Suppressor U1 snRNAs in Drosophila. - Lo,P. C.; Roy,D.; Mount, Stephen M. (GeneticsGenetics, 1994)
Although the role of U1 small nuclear RNAs (snRNAs) in 5' splice site recognition is well established, suppressor U1 snRNAs active in intact multicellular animals have been lacking. Here we describe suppression of a 5' splice site mutation in the Drosophila melanogaster white gene (w(DR18)) by compensatory changes in U1 snRNA. Mutation of positions -1 and +6 of the 5' splice site of the second intron (ACG|GTGACT to ACC|GTGAGC) results in the accumulation of RNA retaining this 74-nucleotide intron in both transfected cells and transgenic flies. U1-3G, a suppressor U1 snRNA which restores basepairing at position +6 of the mutant intron, increases the ratio of spliced to unspliced w(DR18) RNA up to fivefold in transfected Schneider cells and increases eye pigmentation in w(DR18) flies. U1-9G, which targets position -1, suppresses w(DR18) in transfected cells less well. U1-3G,9G has the same effect as U1-3G although it accumulates to lower levels. Suppression of w(DR18) has revealed that the U1b embryonic variant (G134 to U) is active in Schneider cells and pupal eye discs. However, the combination of 9G with 134U leads to reduced accumulation of both U1b-9G and U1b-3G,9G, possibly because nucleotides 9 and 134 both participate in a potential long-range intramolecular base-pairing interaction. High levels of functional U1-3G suppressor reduce both viability and fertility in transformed flies. These results show that, despite the difficulties inherent in stably altering splice site selection in multicellular organisms, it is possible to obtain suppressor U1 snRNAs in flies.

Transforming queries from a relational schema to an object schema: A prototype based on F-logic - Chang,Yahui; Raschid, Louiqa; Dorr, Bonnie J (Methodologies for Intelligent SystemsMethodologies for Intelligent Systems, 1994)

Visualization in the information highway - Gershon,Nahum; Card,Stuart K.; Roth,Steven F.; Shneiderman, Ben (Proceedings of the conference on Visualization '94, 1994)

ADMS: a testbed for incremental access methods - Roussopoulos, Nick; Economou,N.; Stamenas,A. (IEEE Transactions on Knowledge and Data Engineering, 1993)
ADMS is an advanced database management system developed-to experiment with incremental access methods for large and distributed databases. It has been developed over the past eight years at the University of Maryland. The paper provides an overview of ADMS, and describes its capabilities and the performance attained by its incremental access methods. This paper also describes an enhanced client-server architecture that allows an incremental gateway access to multiple heterogeneous commercial database management systems
Keywords: Add-drop multiplexers; ADMS; advanced database management system; client-server architecture; commercial database management systems; Computational modeling; Database systems; distributed databases; heterogeneous DBMS; incremental access methods; incremental gateway; Information retrieval; interoperability; join index; large databases; Navigation; network operating systems; Object oriented databases; Object oriented modeling; Query processing; System testing; very large databases; view index; Workstations

A connectionist approach to diagnostic problem solving using causal networks - Reggia, James A.; Peng,Y.; Tuhrim,S. (Information sciences, 1993)

Coupling production systems and database systems: A homogeneous approach - Sellis,T.; Lin,C. C; Raschid, Louiqa (Knowledge and Data Engineering, IEEE Transactions on, 1993)

Development of machining alternatives, based on MRSEVs - Nau, Dana S.; Gupta,S.K.; Kramer,T. R.; Regli,W. C.; Zhang, G. (Computers in Engineering, 1993)
One missing link between CAD and CAM is the lack ofa systematic methodology for generating and evaluating al- ternative ways to manufacture a proposed design. To ad- dress this problem, we are developing a systematic approach for generating and evaluating alternative ways to manufac- ture machined parts, in order to provide information to the designer about the manufacturability of the proposed de- sign, and information to the process engineer about how best to machine the part. This paper describes our overall approach, and how MRSEVs (Material Removal Shape El- ement Volumes, a STEP library of machining features) can be used to support it.

An Experimental Study of Three Dataflow Paradigms in Multithreaded Database Transitive Closure Algorithms on Shared Memory Multiprocessors - Youngmyers,H.; Raschid, Louiqa (Journal of Parallel and Distributed Computing, 1993)
This paper describes an experimental study of three dataflow paradigms, namely, no dataflow, pipelined dataflow, and network dataflow, in multithreaded database transitive closure algorithms on shared memory multiprocessors. This study shows that dataflow paradigm directly influences performance parameters such as the amount of interthread communication, how data are partitioned among the threads, whether access to each page of data is exclusive or shared, whether locks are needed for concurrency control, and how calculation termination is detected. The algorithm designed with no dataflow outperforms the algorithms with dataflow. Approximately linear speedup is achieved by the no dataflow algorithm with sufficient workload and primary memory. An exclusive access working set model and a shared access working set model describe the interactions between two or more threads′ working sets when access to each page of data is exclusive or shared among the threads, respectively. These models are experimentally verified.

Information mediation techniques for problem solving with multiple knowledge servers - Dorr, Bonnie J; Raschid, Louiqa (University of Maryland, 1993)
This paper describes two important information mediation prob-lems that arise when multiple knowledge and data servers are accessed for problem solving. The rst problem is building an intelligent interface be- tween a knowledge server (KS) and a processor (KP) so that queries may be answered intelligently and completely. The second problem is to provide interoperability among multiple KP/KS pairs so that a query may be an- swered using information from multiple sources. We present example scenar- ios which highlight each of these problems and then outline techniques and tasks that are applied towards obtaining a solution. These techniques draw upon disciplines such as query and transaction processing with knowledge bases and machine understanding and translation of natural language. The techniques for solving the information mediation problems described involve parameterized canonical representations (CR) for the KP/KS pairs. The CR will represent possible mappings between a query and the knowledge model and will be used during query transformation to produce a query which will provide more complete and correct answers. Parameterization will help in merging CRs to support interoperability for distributed problem solving.

Interoperable query processing with multiple heterogeneous knowledge servers - Raschid, Louiqa; Chang,Yahui; Dorr, Bonnie J (Proceedings of the second international conference on Information and knowledge management, 1993)

The Interpretation and Recognition of Interfering Strokes - David Doermann; Rosenfeld, A. (IWFHR, 1993)

Investigating touchscreen typing: the effect of keyboard size on typing speed - Sears,Andrew; REVIS,DOREEN; SWATSKI,JANET; CRITTENDEN,ROB; Shneiderman, Ben (Behaviour & Information Technology, 1993)
Abstract Two studies investigated the effect keyboard size has on typing speed and error rates for touchscreen keyboards using the lift-off strategy. A cursor appeared when users touched the screen and a key was selected when they lifted their finger from the screen. Four keyboard sizes were investigated ranging from 24.6 cm to 6.8 cm wide. Results indicate that novices can type approximately 10 words per minute (WPM) on the smallest keyboard and 20 WPM on the largest. Experienced users improved to 21 WPM on the smallest keyboard and 32 WPM on the largest. These results indicate that, although slower, small touchscreen keyboards can be used for limited data entry when the presence of a regular keyboard is not practical. Applications include portable pocket-sized or palmtop computers, messaging systems, and personal information resources. Results also suggest the increased importance of experience on these smaller keyboards. Research directions are suggested.Abstract Two studies investigated the effect keyboard size has on typing speed and error rates for touchscreen keyboards using the lift-off strategy. A cursor appeared when users touched the screen and a key was selected when they lifted their finger from the screen. Four keyboard sizes were investigated ranging from 24.6 cm to 6.8 cm wide. Results indicate that novices can type approximately 10 words per minute (WPM) on the smallest keyboard and 20 WPM on the largest. Experienced users improved to 21 WPM on the smallest keyboard and 32 WPM on the largest. These results indicate that, although slower, small touchscreen keyboards can be used for limited data entry when the presence of a regular keyboard is not practical. Applications include portable pocket-sized or palmtop computers, messaging systems, and personal information resources. Results also suggest the increased importance of experience on these smaller keyboards. Research directions are suggested.

Learning competition and cooperation - Cho,S.; Reggia, James A. (Neural computation, 1993)

Local conditions for phase transitions in neural networks with variable connection strengths - McFadden,F. E; Peng,Y.; Reggia, James A. (Neural networks, 1993)

Logo Recognition - David Doermann; Rivlin,E.; Weiss, I. (University of Maryland, College Park, 1993)

Logo Recognition using Geomentric Invariants - David Doermann; Rivlin,E.; Weiss, I. (ICDAR, 1993)

MANDATE: managing networks using database technology - Haritsa,J. R; Ball,M. O; Roussopoulos, Nick; Datta,A.; Baras,J. S (IEEE Journal on Selected Areas in Communications, 1993)
There has been a growing demand for the development of tools to manage enterprise communication networks. A management information database is the heart of a network management system-it provides the interface between all functions of the network management system and, therefore, has to provide sophisticated functionality allied with high performance. The authors introduce the design of MANDATE (MAnaging Networks using DAtabase TEchnology), a proposed database system for effectively supporting the management of large enterprise networks. The MANDATE design makes a conscious attempt to take advantage of the special characteristics of network data and transactions, and of advances in database technology, to efficiently derive some of the required management functionality
Keywords: Communication networks; database management systems; enterprise communication networks; Heart; Information management; interface; internetworking; Local area networks; management functionality; management information database; managing networks using database technology; MANDATE; Manufacturing; network operating systems; open systems; Optical fiber cables; Research and development management; Technology management; telecommunication network management; Transaction databases; wide area networks

Multiple disorder diagnosis with adaptive competitive neural networks - Cho,S.; Reggia, James A. (Artificial intelligence in medicine, 1993)

Neural computation in medicine - Reggia, James A. (Artificial Intelligence in Medicine, 1993)

Optimal algorithms on the pipelined hypercube and related networks - JaJa, Joseph F.; Ryu,K. W. (Parallel and Distributed Systems, IEEE Transactions on, 1993)
Parallel algorithms for several important combinatorial problems such as the all nearest smaller values problem, triangulating a monotone polygon, and line packing are presented. These algorithms achieve linear speedups on the pipelined hypercube, and provably optimal speedups on the shuffle-exchange and the cube-connected-cycles for any number <e1>p </e1> of processors satisfying 1 les;<e1>p</e1> les;<e1>n</e1>/((log3<e1>n</e1>)(loglog <e1>n</e1>)2), where <e1>n</e1> is the input size. The lower bound results are established under no restriction on how the input is mapped into the local memories of the different processors
Keywords: algorithms; pipeline; algorithms; pipelined; combinatorial; geometry; parallel; hypercube; shuffle-exchange; combinatorial; mathematics; computational; packing; monotone; polygon; parallel; problems; cube-connected-cycles; line; processing

Performance comparison of three modern DBMS architectures - Delis,A.; Roussopoulos, Nick (IEEE Transactions on Software Engineering, 1993)
The introduction of powerful workstations connected through local area networks (LANs) inspired new database management system (DBMS) architectures that offer high performance characteristics. The authors examine three such software architecture configurations: client-server (CS), the RAD-UNIFY type of DBMS (RU), and enhanced client-server (ECS). Their specific functional components and design rationales are discussed. Three simulation models are used to provide a performance comparison under different job workloads. Simulation results show that the RU almost always performs slightly better than the CS, especially under light workloads, and that ECS offers significant performance improvement over both CS and RU. Under reasonable update rates, the ECS over CS (or RU) performance ratio is almost proportional to the number of participating clients (for less than 32 clients). The authors also examine the impact of certain key parameters on the performance of the three architectures and show that ECS is more scalable that the other two
Keywords: client-server; Computational modeling; Computer architecture; database management systems; DBMS architectures; design rationales; functional components; Indexes; Local area networks; Military computing; Packaging; Performance analysis; performance evaluation; RAD-UNIFY type; simulation models; simulation results; Software architecture; software architecture configurations; software engineering; Throughput; Workstations

The processing of form documents - David Doermann; Rosenfeld, A. (Document Analysis and Recognition, 1993., Proceedings of the Second International Conference on, 1993)
An overview of an approach to the generic modeling and processing of known forms is presented. The system provides a methodology by which models are generated from regions in the document based on their usage. Automatic extraction of an optimal set of features to be used for registration is proposed, and it is shown how specialized detectors can be designed for each feature based on their position, orientation and width properties. Registration of the form with the model is accomplished using probing to establish correspondence. Form components which are corrupted by markings are detected and isolated, the intersections are interpreted and the properties of the non-form markings are used to reconstruct the strokes through the intersections. The feasibility of these ideas is demonstrated through an implementation of key components of the system
Keywords: AUTOMATIC; business; detectors; document; documents; extraction; feature; form; forms; generation; generic; handling; known; markings; model; modeling; non-form; optimal; properties; reconstruction; set; specialized; stroke; width

Query mapping and transformation techniques for problem solving with multiple knowledge servers - Raschid, Louiqa; Chang,Y.; Dorr, Bonnie J (Proceedings of the Second International Conference on Information and Knowledge Management (CIKM-93), 1993)
This paper describes a technique for infor-mation mediation when multiple heterogeneous knowl- edge and data servers are to be accessed during query processing. One problem is building an intelligent in- terface between each knowledge server (KS) and its processor (KP); and the second is to provide interoper- ability among multiple KP/KS so that a query may be answered using information from multiple sources. We present example scenarios which highlight these prob- lems and then outline query mapping and transforma- tion techniques that are applicable. The techniques for solving the interoperability problems involve rep- resentations in some canonical form. This includes a canonical representation (CR) corresponding to each KP/KS pair and a merged CR (MCR) to represent the mapping among the CRs. The MCR and CRs include relevant information obtained from a source query, and heterogeneous mapping (het-map) information, for all possible mappings among the multiple servers. The knowledge in the canonical form must be represented so that it can be easily accessed during query transfor- mation. We use an example of translating queries from an object schema to a relational schema to illustrate typical knowledge that must be represented in some canonical form. We use a high level logical language, F-logic, to represent the heterogeneous mapping (het- map) and query transformation information as a set of declarative rules, in the canonical form.

Semantic classes and syntactic ambiguity - Resnik, Philip (Proceedings of the workshop on Human Language Technology, 1993)

Simple systems that exhibit template-directed replication - Reggia, James A.; Armentrout,S. L; Chou,H. H.; Peng,Y. (Science, 1993)

Structural ambiguity and conceptual relations - Resnik, Philip; Hearst,M. (Proceedings of the Workshop on Very Large Corpora: Academic and Industrial Perspectives, 1993)

Transitive closure: an experimental case study of three multithreaded database algorithms on a shared memory multiprocessor - Young-Myers,H.; Raschid, Louiqa (Parallel and Distributed Information Systems, 1993., Proceedings of the Second International Conference on, 1993)

Using differential technlques to efficiently support transaction time - Jensen,Christian S.; Mark,Leo; Roussopoulos, Nick; Sells,Timos (The VLDB JournalVLDB Journal, 1993)

Using MRSEVs to develop machining alternatives - Nau, Dana S.; Gupta,S.K.; Kramer,T. R.; Regli,W. C.; Zhang, G. (1993)

Behavioral Visual Motion Analysis," - Aloimonos, J.; Duriç,Z.; Fermüller, Cornelia; Huang, L.; Rivlin,E.; Sharma, R. (Proceedings, DARPA Image Understanding Workshop, 1992)

A class-based approach to lexical discovery - Resnik, Philip (Proceedings of the 30th annual meeting on Association for Computational Linguistics, 1992)

A competitive distribution theory of neocortical dynamics - Reggia, James A.; D'Autrechy,C. L; Sutton III,G. G.; Weinrich,M. (Neural Computation, 1992)

A connectionist approach to vertex covering problems - Peng,Y.; Reggia, James A.; Li,T. (Int’l J. Neural Systems, 1992)

copia-like retrotransposons are ubiquitous among plants - Voytas,D. F; Cummings, Michael P.; Koniczny,A.; Ausubel,F. M; Rodermel,S. R (Proc Natl Acad Sci USA, 1992)
Transposable genetic elements are assumed to be a feature of all eukaryotic genomes. Their identification, however, has largely been haphazard, limited principally to organisms subjected to molecular or genetic scrutiny. We assessed the phylogenetic distribution of copia-like retrotransposons, a class of transposable element that proliferates by reverse transcription, using a polymerase chain reaction assay designed to detect copia-like element reverse transcriptase sequences. copia-like retrotransposons were identified in 64 plant species as well as the photosynthetic protist Volvox carteri. The plant species included representatives from 9 of 10 plant divisions, including bryophytes, lycopods, ferns, gymnosperms, and angiosperms. DNA sequence analysis of 29 cloned PCR products and of a maize retrotransposon cDNA confirmed the identity of these sequences as copia-like reverse transcriptase sequences, thereby demonstrating that this class of retrotransposons is a ubiquitous component of plant genomes.

Experiments on the concurrent rule execution in database systems - Delis,A.; Raschid, Louiqa; Sellis,T. (Tools with Artificial Intelligence, 1992. TAI'92, Proceedings., Fourth International Conference on, 1992)

Incrementally maintained network→relational database mapping - Mark,Leo; Roussopoulos, Nick; Newsome,Tina; Laohapipattana,Piriya (Software: Practice and Experience, 1992)
An incrementally maintained mapping from a network to a relational database is presented. This mapping may be established either to support the efficient retrieval of data from a network database through a relational interface, or as the first step in a gradual conversion of data and applications from a network to a relational database system. After the mapping has been established, the only data mapped from the network to the relational database are the increments resulting from updates on the network database. The mapping is therefore an efficient alternative to mappings that repeatedly map the results of retrievals through the relational interface from the network database to the relational database. This is in particular the case when the two databases reside on different hosts. Applications on the network database may, under certain restrictions, gradually be moved to the relational database, while the mapping incrementally maintains the relational database for the applications that remain on the network database.
Keywords: Database conversion; Database gateway; Database mapping; Incremental database mapping

Instrument Grasp: AModel and its Effects on Handwritten Strokes - David Doermann; Varma,V.; Rosenfeld, A. (University of Maryland, College Park, 1992)

Lateral cortical inhibition without lateral inhibitory connections - Reggia, James A.; Sutton,G.; D'Autrechy,C. L; Weinrich,M. (Neural Networks, 1992. IJCNN., International Joint Conference on, 1992)
The authors consider how a set of neurons forming a cortical column, none of which individually can competitively distribute its activity, can function collectively to produce competitive distribution of activation. To address this issue, they describe a model cortical column composed of three populations of excitatory neurons that collectively distribute their activity competitively. The idea of competitive distribution and the neural circuitry that could bring it about are described. Computer simulation results, implications, and testable predictions of the theory are presented
Keywords: brain models; competitive distribution of activation; digital simulation; excitatory neurons; lateral cortical inhibition; neural circuitry; neurophysiology; physiological models

Learning visual coordinate transformations with competition - Cho,S.; Reggia, James A. (Neural Networks, 1992. IJCNN., International Joint Conference on, 1992)

Left-corner parsing and psychological plausibility - Resnik, Philip (Proceedings of the 14th conference on Computational linguistics-Volume 1, 1992)

Load balancing and routing on the hypercube and related networks - JaJa, Joseph F.; Ryu,Kwan Woo (Journal of Parallel and Distributed Computing, 1992)
Several results related to the load balancing problem on the hypercube, the shuffle-exchange, the cube-connected cycles, and the butterfly are shown. Implications of these results for routing algorithms are also discussed. Our results include the following: •⊎ Efficient load balancing algorithms are found for the hypercube, the shuffle-exchange, the cube-connected cycles, and the butterfly. • ⊎ Load balancing is shown to require more time on a p-processor shuffle-exchange, cube-connected cycle or butterfly than on a p-processor weak hypercube. • ⊎ Routing n packets on a p-processor hypercube can be done optimally whenever n = p1+1/k, for any fixed k > 0.

A parallel pipelined strategy for evaluating linear recursive predicates in a multiprocessor environment. - Raschid, Louiqa; Su,S. Y.W (J. Parallel Distrib. Comput., 1992)

Probabilistic tree-adjoining grammar as a framework for statistical natural language processing - Resnik, Philip (Proceedings of the 14th conference on Computational linguistics-Volume 2, 1992)

Real-time procedural textures - Rhoades,John; Turk,Greg; Bell,Andrew; State,Andrei; Neumann,Ulrich; Varshney, Amitabh (Proceedings of the 1992 symposium on Interactive 3D graphics, 1992)

Recovery of temporal information from static images of handwriting - David Doermann; Rosenfeld, A. (Proceedings in the IEEE CVPR, 1992)
The problem of off-line handwritten character recognition has eluded a satisfactory solution for several decades. Researchers working in the area of on-line recognition have had greater success, but the possibility of extracting on-line information from static images has not been fully explored. The experience of forensic document examiners assures us that in many cases, such information can be successfully recovered.We outline the design of a system for the recovery of temporal information from static handwritten images. We provide a taxonomy of local, regional and global temporal clues which are often found in hand-written samples, and describe methods for recovering these clues from the image. We show how this system can benefit from obtaining a comprehensive understanding of the handwriting signal and a detailed analysis of stroke and sub-stroke properties. We suggest that the recovery task requires that we break away from traditional thresholding and thinning techniques, and we provide a framework for such analysis. We demonstrate how isolated temporal clues can reliably be extracted from this framework and propose a control structure for integrating the partial information. We show how many seemingly ambiguous situations can be resolved by the derived clues and our knowledge of the writing process, and provide several examples to illustrate our approach. The support of this research by the Ricoh Corporation is gratefully acknowledged.

Semantics for Rule-based Programs that Express Non-determinism, Causality and Exception Handling Behavior - Raschid, Louiqa (Workshop on Deductive Databases, JICSLP, 1992)

Simple systems exhibiting self-directed replication: annex of transition functions and software documentation - Reggia, James A.; Chou,Hui-Hsien; Armentrout,Steven L.; Peng,Yun (University of Maryland at College Park, 1992)

Six Generations of Building Walkthrough: Final Technical Report to the National Science Foundation - Brooks,Frederick P.; Airey,John; Alspaugh,John; Bell,Andrew; Brown,Randolph; Hill,Curtis; Nimscheck,Uwe; Rheingans,Penny; Rohlf,John; Smith,Dana; Turner,Douglass; Varshney, Amitabh; et al. (University of North Carolina at Chapel Hill, 1992)

Software approaches to segmentation analysis - D'Autrechy,C. L; Reggia, James A.; Berndt,R. S (Computer Science Technical Report Series; Vol. CS-TR-2991, 1992)

Structural analysis of hypertexts: identifying hierarchies and useful metrics - Botafogo,Rodrigo A.; Rivlin,Ehud; Shneiderman, Ben (ACM Transactions on Information Systems, 1992)
Hypertext users often suffer from the “lost in hyperspace” problem: disorientation from too many jumps while traversing a complex network. One solution to this problem is improved authoring to create more comprehensible structures. This paper proposes several authoring tools, based on hypertext structure analysis.In many hypertext systems authors are encouraged to create hierarchical structures, but when writing, the hierarchy is lost because of the inclusion of cross-reference links. The first part of this paper looks at ways of recovering lost hierarchies and finding new ones, offering authors different views of the same hypertext. The second part helps authors by identifying properties of the hypertext document. Multiple metrics are developed including compactness and stratum. Compactness indicates the intrinsic connectedness of the hypertext, and stratum reveals to what degree the hypertext is organized so that some nodes must be read before others. Several existing hypertexts are used to illustrate the benefits of each technique. The collection of techniques provides a multifaceted view of the hypertext, which should allow authors to reduce undesired structural complexity and create documents that readers can traverse more easily.
Keywords: graph theory; hierarchies; hypertext; metrics; structural analysis

Temporal clues in handwriting - David Doermann; Rosenfeld, A. (Pattern Recognition, 1992. Vol.II. Conference B: Pattern Recognition Methodology and Systems, Proceedings., 11th IAPR International Conference on, 1992)
Handwritten character recognition is typically classified as online or offline depending on the nature of the input data. Online data consists of a temporal sequence of instrument positions while offline data is in the form of a 2D image of the writing sample. Online recognition techniques have been relatively successful but have the disadvantage of requiring the data to be gathered during the writing process. This paper presents work on the extraction of temporal information from static images of handwriting and its implications for character recognition
Keywords: character; extraction; feature; handwriting; information; offline; online; recognition; techniques; temporal

Wordnet and distributional analysis: A class-based approach to lexical discovery - Resnik, Philip (AAAI workshop on statistically-based natural language processing techniques, 1992)

An algebra and calculus for relational multidatabase systems - Grant,J.; Litwin,W.; Roussopoulos, Nick; Sellis,T. (, First International Workshop on Interoperability in Multidatabase Systems, 1991. IMS '91. Proceedings, 1991)
With the existence of many autonomous databases widely accessible through computer networks, users will require the capability to jointly manipulate data in different databases. A multidatabase system provides such a capability through a multidatabase manipulation language. The authors propose a theoretical foundation for such languages by presenting a multirelational algebra and calculus based on the relational algebra and calculus. The proposal is illustrated by various queries on an example multidatabase
Keywords: Algebra; autonomous databases; Calculus; Computer networks; Computer science; Data models; Data structures; Database systems; database theory; distributed databases; Military computing; multidatabase manipulation language; multidatabase system; multirelational algebra; query languages; relational algebra; Relational databases; Spatial databases; theoretical foundation

Competitive activation mechanisms in connectionist models - Reggia, James A.; Sutton,G.; Cho,S. (Advances in control networks and large-scale parallel distributed processing models, 1991)

An experimental study of criteria for hypothesis plausibility - Tuhrim,S.; Reggia, James A.; Goodall,S. (Journal of Experimental & Theoretical Artificial Intelligence, 1991)

On finding the minimum bandwidth of interval graphs - Mahesh,R.; Rangan,C.Pandu; Srinivasan, Aravind (Information and Computation, 1991)
Let G = (V, E) be an interval graph, with |V| = n, and |E| = m. An O(n2 log n) algorithm was proposed in Kratsch (Inform Comput. 74, 140–158 (1987)) to find the bandwidth of G. We show that this algorithm is wrong, and provide a corrected version of the same. Also, it was observed in [4] that the bandwidth of a proper interval graph can be computed in O(n log n + m) time. We show how this idea can be modified slightly to yield an O(n = m) algorithm.

Incremental implementation model for relational databases with transaction time - Jensen,C. S; Mark,L.; Roussopoulos, Nick (IEEE Transactions on Knowledge and Data Engineering, 1991)
An implementation model for the standard relational data model extended with transaction time is presented. The implementation model integrates techniques of view materialization, differential computation, and deferred update into a coherent whole. It is capable of storing any view (reflecting past or present states) and subsequently using stored views as outsets for incremental and decremental computations of requested views, making it more flexible than previously proposed partitioned storage models. The working and the expressiveness of the model are demonstrated by sample queries that show how historical data are retrieved
Keywords: Computational modeling; Computer science; Data models; data retrieval; Database languages; Database systems; database theory; decremental computations; deferred update; Degradation; differential computation; historical data; History; incremental computations; Information retrieval; partitioned storage models; queries; relational data model; Relational databases; stored views; Transaction databases; transaction time; view materialization

Modern client-server DBMS architectures - Roussopoulos, Nick; Delis,Alexis (ACM SIGMOD RecordSIGMOD Rec., 1991)

A pipeline N-way join algorithm based on the 2-way semijoin program - Roussopoulos, Nick; Kang,H. (IEEE Transactions on Knowledge and Data Engineering, 1991)
The semijoin has been used as an effective operator in reducing data transmission and processing over a network that allows forward size reduction of relations and intermediate results generated during the processing of a distributed query. The authors propose a relational operator, two-way semijoin, which enhanced the semijoin with backward size reduction capability for more cost-effective query processing. A pipeline N-way join algorithm for joining the reduced relations residing on N sites is introduced. The main advantage of this algorithm is that it eliminates the need for transferring and storing intermediate results among the sites. A set of experiments showing that the proposed algorithm outperforms all known conventional join algorithms that generate intermediate results is included
Keywords: 2-way semijoin program; backward size reduction; Bandwidth; Computer networks; Costs; Data communication; data transmission; Database systems; database theory; Delay; distributed databases; distributed query; forward size reduction; intermediate results; Local area networks; network; Parallel algorithms; pipeline N-way join algorithm; pipeline processing; Pipelines; programming theory; Query processing; Relational databases; relational operator; SITES; Workstations

Pyramid computation of neighbor distance statistics in dot patterns - Banerjee,Saibal; Mount, Dave; Rosenfeld,Azriel (CVGIP: Graphical Models and Image Processing, 1991)
This paper describes an algorithm for computing statistics of Voronoi neighbor distances in a dot pattern, using a cellular pyramid computer, in a logarithmic number of computational steps. Given a set of dots in a square region of the digital plane, the algorithm determines with high probability the Voronoi neighbors of the dots in the interior of the region and then computes statistics of the neighbor distances. An algorithm of this type may account for the ability of humans to perceive at a glance whether the dots in a pattern are randomly or regularly spaced, i.e., their neighbor distances have high or low variance.

Recent applications of competitive activation mechanisms - Reggia, James A.; Peng,Y.; Bourret,P. (Neural Networks: Advances and Applications, 1991)

Recovery of Temporal Information from Static Images of Handwriting - David Doermann; Rosenfeld, A. (Center for Automation Research, University of Maryland, 1991)
The problem of off-line handwritten character recognition has eluded a satisfactory solution for several decades. Researchers working in the area of on-line recognition have had greater success, but the possibility of extracting on-line information from static images has not been fully explored. The experience of forensic document examiners assures us that in many cases, such information can be successfully recovered.We outline the design of a system for the recovery of temporal information from static handwritten images. We provide a taxonomy of local, regional and global temporal clues which are often found in hand-written samples, and describe methods for recovering these clues from the image. We show how this system can benefit from obtaining a comprehensive understanding of the handwriting signal and a detailed analysis of stroke and sub-stroke properties. We suggest that the recovery task requires that we break away from traditional thresholding and thinning techniques, and we provide a framework for such analysis. We demonstrate how isolated temporal clues can reliably be extracted from this framework and propose a control structure for integrating the partial information. We show how many seemingly ambiguous situations can be resolved by the derived clues and our knowledge of the writing process, and provide several examples to illustrate our approach. The support of this research by the Ricoh Corporation is gratefully acknowledged.

Semantics for update rule programs and implementation in a relational database management system - Raschid, Louiqa; Lobo,J. (ACM Transactions on Database Systems, 1991)

Trie hashing with controlled load - Litwin,W. A; Roussopoulos, Nick; Levy,G.; Hong,W. (IEEE Transactions on Software Engineering, 1991)
Trie hashing (TH), a primary key access method for storing and accessing records of dynamic files, is discussed. The key address is computed through a trie. A key search usually requires only one disk access when the trie is in core and two disk accesses for very large files when the trie must be on disk. A refinement to trie hashing, trie hashing with controlled load (THCL), is presented. It is designed to control the load factor of a TH file as tightly as that of a B-tree file, allows high load factor of up to 100% for ordered insertions, and increases the load factor for random insertions from 70% to over 85%. It is shown that these properties make trie hashing preferable to a B-tree
Keywords: B-tree file; Computer science; controlled load; Databases; disk access; dynamic files; file organisation; high load factor; information retrieval systems; key search; load factor; Military computing; ordered insertions; Predictive models; primary key access method; Protocols; random insertions; TH file; THCL; Tree data structures; trees (mathematics); trie hashing

Visual recovery - Aloimonos, J.; Rosenfeld, A. (University of Maryland, Center for Automation Research, Computer Vision Laboratory, 1991)

Abductive Inference Models for Diagnostic Problem-Solving - Yun,P.; Reggia, James A. (Springer-Verlag, New York, 1990)

Competitive learning using competitive activation rules - Sutton III,G. G.; Reggia, James A.; Maisog,J. M (Neural Networks, 1990., 1990 IJCNN International Joint Conference on, 1990)

Connectionist models and information retrieval - Doszkocs,T. E; Reggia, James A.; others (Annual review of information science and technology, 1990)

Diagnostic reasoning at multiple levels of abstraction - Chu,B. T.B; Reggia, James A. (AI Systems in Government Conference, 1990. Proceedings., Fifth Annual, 1990)

Efficient algorithms for list ranking and for solving graph problems on the hypercube - Ryu,K. W.; JaJa, Joseph F. (Parallel and Distributed Systems, IEEE Transactions on, 1990)
A hypercube algorithm to solve the list ranking problem is presented. Let <e1>n</e1> be the length of the list, and let <e1>p</e1> be the number of processors of the hypercube. The algorithm described runs in time O(<e1>n</e1>/<e1>p</e1>) when <e1>n</e1>= Omega;(<e1>p</e1> 1+ epsi;) for any constant epsi; gt;0, and in time O(<e1>n </e1> log <e1>n</e1>/<e1>p</e1>+log3 <e1>p</e1>) otherwise. This clearly attains a linear speedup when <e1>n</e1>= Omega;(<e1>p</e1> 1+ epsi;). Efficient balancing and routing schemes had to be used to achieve the linear speedup. The authors use these techniques to obtain efficient hypercube algorithms for many basic graph problems such as tree expression evaluation, connected and biconnected components, ear decomposition, and st-numbering. These problems are also addressed in the restricted model of one-port communication
Keywords: algorithm; hypercube; algorithms; graph; algorithms; linear; algorithms; sorting; balancing; one-port; basic; communication; sorting; st-numbering; tree; complexity; graph; components; ear; decomposition; graph; evaluation; computational; Expression; graph; problems; biconnected; problems; hypercube; ranking; load; speedup; list; theory; parallel

Efficient compilation of large rule bases using logical access paths - Sellis,Timos K.; Roussopoulos, Nick; Ng,Raymond T. (Information Systems, 1990)
This paper presents an efficient way to compile and store large deductive databases. Deductive rules are modeled through logical access paths and then integrated into a global structure, the Rule-base Access Path Schema (RAP Schema). The RAP Schema stores information on the interrelationships that exist among the computations required for rule executions. Ground data as well as data derived through some rule executions and cached for later reuse are also modeled in the RAP Schema. Some of the advantages of using this rule base organization scheme include the automatic detection of shared computations, the inclusion of cached results of rule executions and query results in the knowledge base. The details of the compilation and query processing phases are the focus of the paper.

Inductive inference model for diagnostic problem-solving - Peng,Y.; Reggia, James A. (Springer-Verlag, 1990)

Information interchange between self-describing databases - Mark,Leo; Roussopoulos, Nick (Information Systems, 1990)
Within the framework of a self-describing database system we describe a set of data management tools and a data dictionary supporting information interchange. The concepts are based on our experience from a project on standardized information interchange in NASA.

Interoperability of multiple autonomous databases - Litwin,Witold; Mark,Leo; Roussopoulos, Nick (ACM Computing SurveysACM Comput. Surv., 1990)

Load balancing on the hypercube and related networks - JaJa, Joseph F.; Ryu,K. W. (Proceedings of 1990 International Conference on Parallel Processing, 1990)

Mailpiece Preprocessing: The population of Character Parts - David Doermann; Rosenfeld, A. (ATC, 1990)

Maintaining consistency in a stratified production system program - Raschid, Louiqa (Proceedings of the AAAI National Conference on Artificial Intelligence, 1990)

Modeling diagnostic problem-solving at multiple levels of abstraction - Chu,B.-T.B.; Reggia, James A. (Artificial Intelligence Applications, 1990., Sixth Conference on, 1990)
A precise domain-independent computational model for diagnostic problem-solving at multiple levels of abstraction is presented. The knowledge representation framework allows causal knowledge to be represented in a precise yet natural way that reflects a human diagnostician's experience in guiding diagnostic reasoning at multiple levels of abstraction. The inference mechanism clearly defines how to form plausible diagnostic hypotheses guided by explicit causal links and the principle of parsimonious covering. It permits the efficient formation of high-level diagnostic hypotheses while at the same time ensuring that all plausible diagnostic alternatives will be considered if one wishes to reason at sufficiently detailed levels. A prototype implementation is described to demonstrate that the proposed inference model is natural for capturing a small but representative fragment of medical causal knowledge, and, with the addition of reasonable heuristics, that the inference mechanism exhibits desirable problem-solving behavior
Keywords: causal knowledge; diagnostic problem-solving; diagnostic reasoning; domain-independent computational model; explicit causal links; heuristic programming; heuristics; inference mechanism; inference mechanisms; knowledge capture; knowledge representation; knowledge representation framework; medical knowledge; multiple abstraction levels; parsimonious covering; plausible diagnostic hypotheses; problem solving

Multiple underlying systems: Translating user requests into programs to produce answers - Bobrow,R.J.; Resnik, Philip; Weischedel,R.M. (Proceedings of the 28th annual meeting on Association for Computational Linguistics, 1990)

Optimal view caching - Amir,Amihood; Roussopoulos, Nick (Information Systems, 1990)
A view in a database is a subset of records selected from several files to satisfy some condition, e.g. the join of two relations.It has been shown that it is more efficient to store pointers to the satisfying records of the base relations rather than the complete records of the view. We are interested in efficient caching of such pointers (in effect constructing the view) when the database lies in secondary storage and only a limited number of buffers exists in memory. A view caching is optimal if it is done with the minimum number of reads from secondary storage. We prove that optimal view caching is NP -complete.

Parsimonious covering theory in cognitive diagnosis and adaptive instruction - Reggia, James A.; D'Autrechy,C. L (Diagnostic Monitoring of Skill and Knowledge AcquisitionDiagnostic Monitoring of Skill and Knowledge Acquisition, 1990)

Phase transitions in connectionist models having rapidly varying connection strengths - Reggia, James A.; Edwards,M. (Neural Computation, 1990)

Supervised and reinforced competitive learning - Sutton III,G. G.; Reggia, James A.; Maisog,J. M (Neural Networks, 1990., 1990 IJCNN International Joint Conference on, 1990)

A comfort measure for diagnostic problem solving - Peng,Yun; Reggia, James A. (Information Sciences, 1989)
In order to apply Bayes' theorem for diagnostic problem solving when multiple disorders can occur simultaneously, several previous proposals have suggested using the ratio of posterior probabilities to rank diagnostic hypotheses. Approaches using such relative likelihoods lose the measure of absolute strengths of hypotheses, and thus are incapable of evaluating the “quality” of a problem solution. In this paper, we propose to impose a quantity called a “comfort measure” on the solution: a solution of a diagnostic problem is a minimal-size set of hypotheses such that the sum of their posterior probabilities exceeds a given comfort measure. Based on a probabilistic causal model developed previously, a problem-solving strategy is presented which does not require the manifestation independence assumption required with direct Bayesian classification, and which is applicable to multimembership classification problems. This strategy selectively generates diagnostic hypotheses and calculates both their relative likelihood and the lower and upper bounds of their posterior probabilities. These bounds are successively refined as more hypotheses are generated. Using these bounds, not the real posterior probabilities, the problem-solving strategy identifies a solution satisfying the given comfort measure, usually after only a small portion of all possible hypotheses have been generated.

A connectionist model for diagnostic problem solving - Peng,Y.; Reggia, James A. (Systems, Man and Cybernetics, IEEE Transactions on, 1989)

A connectionist model for dynamic control - Whitfield,K. C; Goodall,S. M; Reggia, James A. (Telematics and Informatics, 1989)

A data flow implementation of a competition-based connectionist model* 1 - Tagamets,M. A; Reggia, James A. (Journal of Parallel and Distributed Computing, 1989)

Dynamic bin packing problem - Dikshit,Piyush; Guimaraes,Katia; Ramamurthy,Maya; Agrawala, Ashok K.; Larsen,Ronald L (SIAM Journal on Computing, 1989)
In a previous work we have defined a general architecture model for autonomous systems, which can be mapped easily to describe the functions of any automated system (SDAG-86-01). In this note, we use the model to describe the problem of thermal management in space stations. First we briefly review the architecture, then we present the environment of our application, and finally we detail the specific function for each functional block of the architecture for that environment.

Efficient Techniques for Routing and for Solving Graph Problems on the Hypercube - JaJa, Joseph F.; Ryu,K. W. (University of Maryland, 1989)

Functional and psychosocial effects of multimodality limb-sparing therapy in patients with soft tissue sarcomas - Chang,A. E; Steinberg,S. M; Culnane,M.; Lampert,M. H; Reggia, James A.; Simpson,C. G; Hicks,J. E; White,D. E; Yang,J. J; Glatstein,E. (Journal of Clinical Oncology, 1989)

Generating plausible diagnostic hypotheses with self-processing causal networks - Wald,J.; Farach,M.; Tagamets,M.; Reggia, James A. (Journal of Experimental & Theoretical Artificial Intelligence, 1989)

Lessons learned from the ACM hypertext on hypertext project - Rous,B.; Shneiderman, Ben; Yankelovich,N.; Yoder,E. (Proceedings of the second annual ACM conference on Hypertext, 1989)

List ranking on the Hypercube - Ryu,K. W.; JaJa, Joseph F. (Proceedings of the 1989 International Conference on Parallel Processing, 1989)

A method for interactive satellite failure diagnosis: Towards a connectionist solution - Bourret,P.; Reggia, James A. (NASA. Goddard Space Flight Center, The 1989 Goddard Conference on Space Applications of Artificial Intelligence p 143-152(SEE N 89-26578 20-63), 1989)

Methods for deriving competitive activation mechanisms - Reggia, James A. (Neural Networks, 1989. IJCNN., International Joint Conference on, 1989)
Inhibitory interactions in connectionist models have traditionally been implemented using inhibitory connections. Recently, an alternative approach based on competitive activation mechanisms has been proposed. To make this alternative approach practical in large and complex models, it is necessary to formulate general methods for creating task-specific competitive activation mechanisms. The author presents two such methods that have been applied successfully: heuristic computer-assisted search and decomposition of global optimization criteria. The usefulness of these two methods is demonstrated through simulations that establish the effectiveness of the competitive activation mechanisms so produced.<<ETX>>
Keywords: connectionist models; decomposition; global optimization criteria; heuristic computer-assisted search; neural nets; optimisation; search problems; task-specific competitive activation mechanisms; virtual machines

Optimal parallel algorithms for one-layer routing - Chang,S. C.; JaJa, Joseph F.; Ryu,K. W. (Instititue for Advanced Computer Studies, Univ of Maryland, College Park, 1989)

Parallel plan execution with self-processing networks - D'Autrechy,C. L; Reggia, James A. (Telematics and Informatics, 1989)

Parsimonious covering as a method for natural language interfaces to expert systems* 1 - Dasigi,V. R; Reggia, James A. (Artificial Intelligence in Medicine, 1989)

Analysis of competition-based spreading activation in connectionist models - Wang,P. Y; Seidman,S. B; Reggia, James A. (International journal of man-machine studies, 1988)

Artificial neural systems in medical science and practice. - Reggia, James A. (MD computing: computers in medical practice, 1988)

Competitive dynamics in a dual-route connectionist model of print-to-sound transformation - Reggia, James A.; Marsland,P. M; Berndt,R. S (Complex Systems, 1988)

The decomposition of a rectangle into rectangles of minimal perimeter - Kong,T.Y; Mount, Dave; Roscoe,AW (SIAM Journal on Computing, 1988)
This paper solves the problem of subdividing a unit square into p rectangles of area 1/p in such a way that the maximal perimeter of a rectangle is as small as possible. The correctness of the solution is proved using the well-known theorems of Menger and Dilworth.

Deep compilation of large rule bases - Sellis,T.; Roussopoulos, Nick (Proceedings 2nd International Conference on Expert Database Systems, 1988)

Efficient parallel triconnectivity in logarithmic time - Ramachandran,V.; Vishkin, Uzi (VLSI Algorithms and Architectures, 1988)

An efficient pictorial database system for PSQL - Roussopoulos, Nick; Faloutsos,C.; Sellis,T. (IEEE Transactions on Software Engineering, 1988)
Pictorial databases require efficient and direct spatial search based on the analog form of spatial objects and relationships instead of search based on some cumbersome alphanumeric encodings of the pictures. A description is given of PSQL, a query language that allows pictorial domains to be presented to the user in their analog form and allows him or her to do direct manipulation on the objects found on those domains. Direct spatial search and computation on the pictures is done using efficient data structures, R- and R+-trees (multidimensional B-trees), which are excellent devices for searching spatial objects and relationships found on pictures
Keywords: alphanumeric encodings; Computer science; Data structures; Database languages; database management systems; Database systems; Encoding; Image coding; Image databases; multidimensional B-trees; Object oriented databases; pictorial database system; PSQL; query language; query languages; R+-trees; Relational databases; Spatial databases; spatial objects; spatial search; User interfaces

Expert database systems: Efficient support for engineering environments - Sellis,T.; Roussopoulos, Nick; Mark,L.; Faloutsos,C. (Data & Knowledge Engineering, 1988)
Manufacturing and Engineering processes use both large scale data and knowledge bases, and the use of expert systems in such environments has become a necessity. Expert Database Systems have evolved from conventional database systems to meet the requirements of current Artificial Intelligence applications. However, future Expert Database Systems will contain knowledge bases of significant size which makes main memory insufficient and the use of a database system a necessity. We propose an effective way of building High Performance Expert Database Systems to support manufacturing and engineering environments. These systems are based on Incremental Computation Models; such models utilize results of previous computations by merging them with newly derived results of computations on small increments representing changes in the database. Our system will be able to support very large knowledge bases by utilizing novel structures and access methods and by using a very sophisticated inference engine based on incremental computation models.
Keywords: engineering databases; Expert database systems; high performance systems; incremental computation models

Expert system development: letting the domain specialist directly author knowledge bases - Tuhrim,S.; Reggia, James A.; Floor,M. (Expert systems: the user interface, 1988)

A general-purpose simulation environment for developing connectionist models - D'Autrechy,C. L; Reggia, James A.; Sutton,G. G; Goodall,S. M (Simulation, 1988)

The Maryland approach to image understanding - Aloimonos, J.; Davis, Larry S.; Rosenfeld, A. (Science Applications International Corp, Proceedings: Image Understanding Workshop,, 1988)

Parallel set covering algorithms - Sekar,S.; Reggia, James A. (Artificial Intelligence Applications, 1988., Proceedings of the Fourth Conference on, 1988)
The authors develop some parallel algorithms for set covering. A brief introduction is given into the parsimonious set covering theory, and algorithms using one type of parsimony called irredundancy are developed. They also discuss several machine-independent parallel constructs that are used to express the parallel algorithms. The algorithms were tested on the Butterfly parallel processor system. The authors present some of the tests conducted and their analyses. Finally, the merits and limitations of the algorithms that were identified during the tests are presented
Keywords: Butterfly parallel processor system; irredundancy; Parallel algorithms; parsimonious set covering theory; set covering; set theory

Partial Revertants of the Transposable Element-Associated Suppressible Allele White-Apricot in Drosophila Melanogaster: Structures and Responsiveness to Genetic Modifiers - Mount, Stephen M.; Green,M. M.; Rubin,G. M. (GeneticsGenetics, 1988)
The eye color phenotype of white-apricot (w(a)), a mutant allele of the white locus caused by the insertion of the transposable element copia into a small intron, is suppressed by the extragenic suppressor suppressor-of-white-apricot (su(w(a))) and enhanced by the extragenic enhancers suppressor-of-forked su(f)) and Enhancer-of-white-apricot (E(w(a))). Derivatives of w(a) have been analyzed molecularly and genetically in order to correlate the structure of these derivatives with their response to modifiers. Derivatives in which the copia element is replaced precisely by a solo long terminal repeat (sLTR) were generated in vitro and returned to the germline by P-element mediated transformation; flies carrying this allele within a P transposon show a nearly wild-type phenotype and no response to either su(f) or su(w(a)). In addition, eleven partial phenotypic revertants of w(a) were analyzed. Of these, one appears to be a duplication of a large region which includes w(a), three are new alleles of su(w(a)), two are sLTR derivatives whose properties confirm results obtained using transformation, and five are secondary insertions into the copia element within w(a). One of these, w(aR84h), differs from w(a) by the insertion of the most 3' 83 nucleotides of the I factor. The five insertion derivatives show a variety of phenotypes and modes of interaction with su((f) and su(w(a)). The eye pigmentation of w(aR84h) is affected by su(f) and E(w(a)), but not su(w(a)). These results demonstrate that copia (as opposed to the interruption of white sequences) is essential for the w(a) phenotype and its response to genetic modifiers, and that there are multiple mechanisms for the alteration of the w(a) phenotype by modifiers.

Self-processing networks and their biomedical implications - Reggia, James A.; Sutton III,G. G. (Proceedings of the IEEE, 1988)

Analysis of object oriented spatial access methods - Faloutsos,C.; Sellis,T.; Roussopoulos, Nick (ACM SIGMOD Record, 1987)

On Cost-effectiveness of a Semijoin in Distributed Query Processing. - Kang,Hyunmo; Roussopoulos, Nick (Institute for Systems Research, University of Maryland, College Park, 1987)
The cost-effective reduction of relations by semijoins is the basis of the heuristic approach to distributed query processing. The cost-effectiveness of a semijoin was simply determined in the literature assuming that the local processing cost is negligible compared to the data transmission cost in distributed query processing. However, recently questions have been raised about the validity of the assumption, and some experimental works revealed that the local processing cost is also significant in distributed query processing. In this paper, we are concerned with the cost-effectiveness of a semijoin considering the local processing cost as well as the data transmission cost. To measure the effectiveness of a semijoin in terms of the local processing cost, we introduce the join sequence in which the relations are joined at the result site to answer the query. A dynamic programming algorithm is developed to generate the optimal join sequence for a given query. A simple heuristic algorithm is also developed to generate a join sequence for a given query.
Keywords: Technical Report

Diagnostic problem-solving with causal chaining - Peng,Y.; Reggia, James A. (International Journal of Intelligent Systems, 1987)

Fine and Medium Grained Parallel Algorithms for Matrix QR Factorization - O'Leary, Dianne P. (Algorithms and Applications on Vector and Parallel ComputersAlgorithms and Applications on Vector and Parallel Computers, 1987)

Meta-Data Management. - Mark,Leo; Roussopoulos, Nick (Institute for Systems Research, University of Maryland, College Park, 1987)
A database system should support a rich variety of meta-data describing and controlling the management and use of data. Few present database systems provide even rudimentary integrated meta-data management facilities.
Keywords: Technical Report

Modeling diagnostic reasoning: a summary of parsimonious covering theory - Reggia, James A.; Peng,Y. (Computer methods and programs in biomedicine, 1987)

A probabilistic causal model for diagnostic problem solving (parts 1 and 2) - Peng,Y.; Reggia, James A. (IEEE Transactions on Systems, Man and Cybernetics, 1987)

Properties of a competition-based activation mechanism in neuromimetic network models - Reggia, James A. (Proceedings of the First International Conference on Neural Networks, 1987)

The R+-tree: A dynamic index for multi-dimensional data - Sellis,T.; Roussopoulos, Nick; Faloutsos,C. (Proceedings of VLDB 1987, 1987)

Structure from Motion from Line Correspondencies: New Results - Science, University of Maryland at College Park. Dept. of Computer; Spetsakis, M. E; Aloimonos, J.; Research, University of Maryland at College Park. Center for Automation (1987)

Using 2-way Semijoins in Distributed Query Processing. - Kang,Hyunmo; Roussopoulos, Nick (Institute for Systems Research, University of Maryland, College Park, 1987)
In distributed query processing, the semijoin has been used as an effective operator in reducing relations referenced in the query to reduce the total amount of data transmission. In this paper, we propose a new relational algebra operator, 2-way semijoin, which is an extended version of the semijoin, for more cost- effective distributed query processing. The 2-way semijoin is compared to the semijoin in terms of the reduction power and the propagation of reduction effects. We show that the 2-way semijoin has more reduction power than the semijoin and that the propagation of reduction effects by the 2-way semijoin is further than by the semijoin.
Keywords: Technical Report

Is Bigger Better?: The Effects of Display Size on Program Reading - Reisel,J.F.; Shneiderman, Ben (Tech Report HCIL-86-08, 1986)
An experiment was conducted in which four window sizes (10, 22, 60 and 120 lines) were compared for their effectiveness for program reading. The largest window, in which the entire program could be seen at one time, was found significantly better, in both time to complete the reading task and the number of correct answers in the reading task. Subjects also preferred the larger windows to the smaller windows.

A comparative analysis of methods for expert systems - Ramsey,C. L; Reggia, James A.; Nau, Dana S.; Ferrentino,A. (International journal of man-machine studies, 1986)

Confidence Intervals for Inequality-Constrained Least Squares Problems, with Applications to Ill-Posed Problems - O'Leary, Dianne P.; Rust,B. W. (SIAM Journal on Scientific and Statistical Computing, 1986)
Computing confidence intervals for functions b(x) wT"x,where Kx y + e and e is a normallydistributed error vector, is a standard problem in multivariate statistics. In this work, we develop an algorithm for solving this problem if additional information, x->0, is given. Applications to estimating solutions to integral equations of the first kind are given.

Engineering Information Systems: Builders and Designers Perspective - Roussopoulos, Nick (SIGMOD Conference, 1986)

Modelling reading aloud and its relevance to acquired dyslexia - Reggia, James A.; Berndt,R. S (Computer methods and programs in biomedicine, 1986)

A parallel processing strategy for evaluating recursive queries - Raschid, Louiqa; Su,S. Y.W (Proceedings of the 12th International Conference on Very Large Data Bases, 1986)

The parsimonious covering model for inexact abductive reasoning in diagnostic systems - Ahuja,S. B; Reggia, James A. (Recent Developments in the Theory and Applications of Fuzzy Sets. Proceedings of NAFIPS, 1986)

Principles and techniques in the design of ADMS+((advanced data-base management system)) - Roussopoulos, Nick; Kang,H. (Computer, 1986)

Relationships between deductive and abductive inference in knowledge-based diagnostic problem solving - Nau, Dana S.; Reggia, James A. (Expert Database Systems: Proceedings of the First International Workshop. New York: Benjamin Cummings, 1986)

A Special-Function Unit for Sorting and Sort-Based Database Operations - Raschid, Louiqa; Fei,T.; Lam,H.; Su,S. Y.W (IEEE Transactions on Computers, 1986)
Achieving efficiency in database management functions is a fundamental problem underlying many computer applications. Efficiency is difficult to achieve using the traditional general-purpose von Neumann processors. Recent advances in microelectronic technologies have prompted many new research activities in the design, implementation, and application of database machines which are tailored for processing database management functions. To build an efficient system, the software algorithms designed for this type of system need to be tailored to take advantage of the hardware characteristics of these machines. Furthermore, special hardware units should be used, if they are cost- effective, to execute or to assist the execution of these software algorithms.
Keywords: Application software; Computer applications; Database machines; Hardware; hardware sorter; Microelectronics; Software algorithms; Software design; Software systems; sort-based algorithms for database operations; sorting; special-function processor; Technology management

Using abductive inferencing to derive complex error classifications for discrete sequential processes - Ahuja,S. B; Reggia, James A. (Proceedings of the 19th annual symposium on Simulation, 1986)

Abductive inference - Reggia, James A. (Proceedigns of the Expert Systems in Government Symposium, 1985)

Answer justification in abductive expert systems for diagnostic problem solving - Reggia, James A.; Perricone,B.; Nau, Dana S.; Peng,Y. (IEEE Transactions on Biomedical Engineering, 1985)

Answer Justification in Diagnostic Expert Systems-Part II: Supporting Plausible Justifications - Reggia, James A.; Perricone,B. T.; Nau, Dana S.; Peng,Y. (Biomedical Engineering, IEEE Transactions on, 1985)

Complete nucleotide sequence of the Drosophila transposable element copia: homology between copia and retroviral proteins. - Mount, Stephen M.; Rubin,G. M. (Molecular and Cellular BiologyMol. Cell. Biol., 1985)
We have determined the complete nucleotide sequence of the copia element present at the white-apricot allele of the white locus in Drosophila melanogaster. This transposable element is 5,146 nucleotides long and contains a single long open reading frame of 4,227 nucleotides. Analysis of the coding potential of the large open reading frame, which appears to encode a polyprotein, revealed weak homology to a number of retroviral proteins, including a protease, nucleic acid-binding protein, and reverse transcriptase. Better homology existed between another part of the copia open reading frame and a region of the retroviral pol gene recently shown to be distinct from reverse transcriptase and required for the integration of circular DNA forms of the retroviral genome to form proviruses. Comparison of the copia sequence with those of the Saccharomyces cerevisiae transposable element Ty, several vertebrate retroviruses, and the D. melanogaster copia-like element 17.6 showed that Ty was most similar to copia, sharing amino acid sequence homology and organizational features not found in the other genetic elements.

Direct spatial search on pictorial databases using packed R-trees - Roussopoulos, Nick; Leifker,D. (ACM SIGMOD Record, 1985)

DS Nau, and PY Wang. A formal model of diagnostic inference - Reggia, James A. (Information Sciences, 1985)

Dynamic access control for relational views. - Roussopoulos, Nick; Bader,C. (INFO. SYST., 1985)

Evaluation of Medical Expert Systems: A Case Study in Performance Analysis - Reggia, James A. (Proceedings of the Ninth Annual Symposium on Computer Applications in Medical Care, 1985)

A formal model of abductive inference - Reggia, James A.; Nau, Dana S.; Wang,P.; Peng,Y. (Information Sciences, 1985)

A formal model of diagnostic inference, II. Algorithmic solution and application - Reggia, James A.; Nau, Dana S.; Wang,P. Y; Peng,Y. (Information Sciences, 1985)

Schema manipulation in self-describing and self-documenting data models - Roussopoulos, Nick; Mark,L. (International Journal of Parallel Programming, 1985)

SEES—A Software testing Environment Support System - Roussopoulos, Nick; Yeh,R. T (IEEE Transactions on Software Engineering, 1985)
SEES is a database system to support program testing. The program database is automatically created during the compilation of the program by a compiler built using the YACC compiler-compiler.
Keywords: Computer architecture; Database systems; Error correction; Program processors; Programming profession; Relational databases; Software testing; software tools; Workstations; Writing

SELF-DESCRIBING AND SELF-DOCUMENTING DATABASE SYSTEMS - Roussopoulos, Nick; Mark,L. (Languages for automation, 1985)

A theoretical foundation for abductive expert systems - Reggia, James A.; Nau, Dana S.; Peng,Y.; Perricone,B. (North-Holland, New York, 1985)

A timed petri net methodolgoy for specifying real-time system timing requirements - Coolahan Jr,J. E; Roussopoulos, Nick (International Workshop on Timed Petri Nets, 1985)

An abductive non-monotonic logic - Reggia, James A.; Nau, Dana S. (Workshop on Nonmonotonic Reasoning, 1984)

Computer-aided assessment of transient ischemic attacks. A clinical evaluation. - Reggia, James A.; Tabb,D. R.; Price,T. R.; Banko,M.; Hebel,R. (Archives of neurology, 1984)

A framework for self-describing and self-documenting database systems - Roussopoulos, Nick; Mark,L. (NBS Trends and Application Conference, 1984)

GDDT--A graphical design and documentation tool for software development - Roussopoulos, Nick; Kelley,Stephen (Computers & Graphics, 1984)
This paper describes "The Graphical Design and Documentation Tool" (GDDT), a general purpose support system for design and documentation. Self documentation and ease of use are presented as important criteria for such tools. Interactive graphics is introduced as a methodology for creating and maintaining hierarchical representations. The graphical representations of various requirements specification techniques and design tools are supported by an extended network model which supports hierarchical decomposition of structures. GDDT is proposed as a general purpose design tool which supports the most common logical constructions of both requirements specification and design methodologies and yet has a high level human interface which makes it easy to learn and use.

An introduction to PSQL: A pictorial structured query language - Roussopoulos, Nick; Leifker,D. (Proc. IEEE Workshop on Visual Languages, 1984)

Monitoring an Ada software development - Basili, Victor R.; Chang,Shih; Gannon,John; Katz,Elizabeth; Panlilio-Yap,N. Monina; Ramsey,Connie Loggia; Zelkowitz, Marvin V; Bailey,John; Kruesi,Elizabeth; Sheppard,Sylvia (ACM SIG Ada Letters, 1984)

A Programming Environment Framework Based on Reusability - Yeh,Raymond T.; Mittermeir,Roland; Roussopoulos, Nick; Reed,Joylyn (Proceedings of the First International Conference on Data Engineering, 1984)

Simulation of phonemic errors using artificial intelligence symbol processing techniques - Reggia, James A.; Ahuja,S. B (Proceedings of the 17th annual symposium on Simulation, 1984)

SLIPS - Morris,M. S; Reggia, James A.; Ahuja,S. B; Hart,J.; Watson,V. (Journal of Medical Systems, 1984)

Achievements and Prospects with Regard to Energy Recycling in Textile Finishing Shops - Pop, Mihai; Romas, D.; Romania (UN, 1983)

The case for artificial intelligence in medicine - Reggia, James A. (Computer Applications in Medical Care, 1983. Proceedings. The Seventh Annual Symposium on, 1983)

Diagnostic expert systems based on a set covering model - Reggia, James A.; Nau, Dana S.; Wang,P. Y (International Journal of Man-Machine Studies, 1983)

Evaluating multiple coordinated windows for programming workstations - Shneiderman, Ben; GRANTHAM,C.; Norman,K.; ROGERS,J.; Roussopoulos, Nick (NASA. Goddard Space Flight Center Proc. of the Eighth Ann. Software Eng. Workshop 11 p(SEE N 84-23137 13-61), 1983)
Programmers might benefit from larger screens with multiple windows or multiple screens, especially if convenient coordination among screens are arranged. Uses for multiple coordinated displays in a programmers workstation are explored. Initial efforts focus on the potential applications, a command language for coordinating the displays, and the psychological basis for effective utilization so as to avoid information overload. Subsequent efforts will be devoted to implementing the concepts and performing controlled psychologically oriented experiments to validate the hypotheses.

Expert systems based on set covering model - Reggia, James A.; Dana,S. N.; Pearl,Y. W. (International Journal on Man-Machine Studies, 1983)

Multi-resolution relaxation - Narayanan,K. A.; O'Leary, Dianne P.; Rosenfeld,Azriel (Pattern Recognition, 1983)
Several types of iterative methods can be used to segment the pixels in an image into light and dark regions; these include “relaxation” methods of probability adjustment and steepest-descent methods of cost function minimization. Conventionally, these methods operate on the image at a single resolution. This paper investigates the possibility of using these approaches at two (or more) resolutions in order to reduce their computational cost—e.g. first obtain an approximate solution by iterating at low resolution, then refine the solution using a few iterations at high resolution.
Keywords: Multigrid methods; Pyramids; Relaxation; segmentation

A New Inference Method for Frame-based Expert System - Reggia, James A.; Nau, Dana S.; Wang,P. Y (Proceedings of the National Conference on Artificial Intelligence, 1983)

A Relational Database to Support Graphical Design and Documentation - Roussopoulos, Nick; Kelley,S. (Databases for Business and Office Applications, Database Week, 1983)

The Role of Spatial Knowledge in Expert Systems - Reggia, James A. (Representation and Processing of Spatial Knowledge, TR-1275. Dept. of Comp. sci „Univ. of Maryland, May, 1983)

S., Wang. PY, Diagnostic Expert Systems Based on a Set Covering Model - Reggia, James A.; Nau, Dana S. (International Journal on Man-Machine studies, 1983)

A self-describing meta-schema for the RM/T data model - Roussopoulos, Nick; Mark,L. (IEEE Workshop On Languages for Automation, IEEE Computer Society Press, 1983)

Small Ribonucleoproteins from Eukaryotes: Structures and Roles in RNA Biogenesis - Steitz,J. A.; Wolin,S. L.; Rinke,J.; Pettersson,I.; Mount, Stephen M.; Lerner,E. A.; Hinterberger,M.; Gottlieb,E. (Cold Spring Harbor Symposia on Quantitative BiologyCold Spring Harb Symp Quant Biol, 1983)
Detailed reviews describing work presented at the annual Cold Spring Harbor Symposia on Quantitative Biology

Timing Requirements for Time-Driven Systems Using Augmented Petri Nets - Coolahan,J. E.; Roussopoulos, Nick (IEEE Transactions on Software Engineering, 1983)
A methodology for the statement of timing requirements is presented for a class of embedded computer systems. The notion of a "time-driven" system is introduced which is formalized using a Petri net model augmented with timing information. Several subclasses of time-driven systems are defined with increasing levels of complexity. By deriving the conditions under which the Petri net model can be proven to be safe in the presence of time, timing requirements for modules in the system can be obtained. Analytical techniques are developed for proving safeness in the presence of time for the net constructions used in the defined subclasses of time-driven systems.
Keywords: Application software; Concurrent computing; Control systems; Embedded computing; Embedded system; Helium; Modeling methodology; performance specifications; Petri nets; Power system modeling; Real time systems; real-time systems; Timing; timing requirements

Transferability of medical decision support systems based on Bayesian classification - Zagoria,R. J; Reggia, James A. (Medical Decision Making, 1983)

Image Smoothing and Segmentation by Cost Minimization - Narayanan,K. A.; O'Leary, Dianne P.; Rosenfeld,Azriel (IEEE Transactions on Systems, Man, and Cybernetics, 1982)

KMS reference manual - Reggia, James A.; Perricone,B. (Dep. Comput. Sci., Univ. Maryland, College Park, Tech. Rep. TR-1136, 1982)

The Logical Access Path Schema of a Database - Roussopoulos, Nick (IEEE Transactions on Software Engineering, 1982)
A new schema which models the usage of the logical access paths of the database is proposed. The schema models all database activities (i.e., retrievals and updates), and integrates their logical access paths by recognizing common subpaths and increasing the "weight" of the shared subpaths. The logical access path schema provides a comprehensive picture of the logical access paths, and the cumulative usage of the shared subpaths and/or intermediate results. The schema serves a dual purpose. Firstly, it is used as a model of the access requirements during the database design, and secondly, as the basis for optimization during the operation of the database.
Keywords: Aggregation hierarchy; Calculus; Computer science; Data structures; Databases; Design optimization; external logical subschema; generalization hierarchy; Information retrieval; Joining processes; logical access path; propositional calculus; views

An Optimization Approach to Edge Reinforcement - Narayanan,K. A.; O'Leary, Dianne P.; Rosenfeld,Azriel (IEEE Transactions on Systems, Man, and Cybernetics, 1982)
The present investigation is concerned with an optimization approach to edge reinforcement which does not involve probabilistic concepts. A cost function is defined, based on the local pattern of edge responses, which is low for sharp, strong edges, and a steepest descent method is used to adjust the edge magnitudes so as to reduce the value of this cost function. The edge reinforcement results obtained in this way appear to be better than those obtained by relaxation methods, whether based on conditional probability or on optimization. The results of an application of the considered procedure to a portion of a Landsat scene are shown, taking into account the input image, the results of 10 iterations of the steepest descent procedure, results produced by means of the relaxation process reported by Schachter et al. (1977), and results obtained with the aid of the optimization relaxation process considered by Faugeras and Berthod (1979).

View indexing in relational databases - Roussopoulos, Nick (ACM Transactions on Database SystemsACM Trans. Database Syst., 1982)

Bayesian classification in medicine: The transferability question - Zagoria,R.; Reggia, James A.; Price,T.; Banko,M. (Proceedings of the Fifth Annual Symposium on Computer Applications in Medical Care, 1981)

Computer-assisted medical decision making: a critical review - Reggia, James A. (Annals of biomedical engineering, 1981)

Knowledge-based decision support systems: Development through high-level languages - Reggia, James A.; Perricone,B. T. (Proc. 20th Ann. Tech. Meeting of Wash. DC ACM, 1981)

An Algorithm for Mutual Exclusion in Computer Networks. - Agrawala, Ashok K.; Ricart, G. (Department of Computer Science, University of Maryland, College Park, 1980)
An algorithm is proposed which creates mutual exclusion in a computer network whose nodes can communicate only by messages and do not share memory. The algorithm sends only 2*(N-1) Messages, where N is the number of nodes in the network, per critical section invocation. This number of messages is a minimum if parallel, distributed, symmetric control is used; hence, the algorithm is optimal in this minimal under some general assumptions. Like Lamport's 'bakery algorithm,' unbounded sequence numbers are used to provide first-come first-served priority into the critical section. It is shown that the number can be contained in a fixed amount of memory by storing it as the residue of a modulus. The number of messages required to implement the exclusion can be reduced by using sequential node-by-node processing, by using broadcast message techniques or by sending information through timing channels. The readers and writers problem is solved by a simple modification of the algorithm. The modifications necessary to make the algorithm robust are described.

Approximate pattern matching in a pattern database system - Davis, Larry S.; Roussopoulos, Nick (Information Systems, 1980)
This work is concerned with the organization of a large database of binary pictures (normalized for size, rotation and position) and with the efficient "inexact match" of an input pattern against the whole database. Current techniques in pattern analysis use matching algorithms without any regard to the global organization of the storage representations of the models they are to match. Consequently, the algorithms are only practical for small databases. This paper discusses the design of a pattern database system and the economy that it provides for the matching problem. The database organization is based on the quad-tree representation of binary patterns. Given an arbitrary decomposition D (or partition) of a pattern P and an arbitrary function f on the pattern, we repeatedly apply f on D(P), D(D(P))P, ... to obtain higher and higher levels of abstraction f(D)(P)), f(D(D(P))), ... of the pattern. The computed values obtained after the jth application of f are used to label the ith level of the pyramid. The specific representation used in this paper is called the sum-quad-tree, in which each level of the tree stores the sum of the labels of its sons. The lowest level of the sum-quad-tree corresponds to the individual pixels and is the nth level (i.e. node m at level n implies v(m) = 0 or v(m) = 1). Nodes at the jth level of the sum-quad-tree correspond to sums of 2n-j × 2n-j picture points, so that the 0th level contains the number of 1's in the pattern. The pyramid representation is used as a hierarchical (n-level) indexing scheme of the database. The advantage of this organization is that the matching algorithms presented reject most of the patterns in the database by utilizing the relatively small in size index tables and thus avoid the overhead of unnecessary CPU time and operation between main memory and secondary storage.

The Effect of the Future in Work Distribution. - Agrawala, Ashok K.; Ricart, G. (COMPUTER SCIENCE CENTER, UNIVERSITY OF MARYLAND COLLEGE PARK, 1980)
A controller is considered which routes arrivals among several servers of different speeds. A decision which sends work to the server which will complete it soonest does not optimize the average completion time (mean flow time) because it doesn't take into account the impact of the decision on future arrivals. This impact on future arrivals, the 'future effect', can be significant at high arrival rates. An estimate of the size of the future effect is derived and controllers which take it into account in routing decisions can reduce the average completion time to near optimum. The effect is most pronounced when the service requirements for arrivals are nearly constant, server speeds are markedly different, and the arrival rate is close to the system's capacity. A controller considering the future effect will more heavily weigh a potential server's backlog than the arrival's service time when making a routing decision

Systematic Derivation of Software Requirements - Yeh,R. Y; Roussopoulos, Nick; Chang,P. (Proceedings of the 1st International Conference on the Entity-Relationship Approach to Systems Analysis and Design, 1980)

Foundations of microprogramming: architecture, software, and applications - Agrawala, Ashok K.; Rauscher,T. G (Academic Press, 1976)

A Generalized Conjugate Gradient Method for the Numerical Solution of Elliptic Partial Differential Equations - Concus,Paul; Golub, Gene H.; O'Leary, Dianne P. (Sparse Matrix ComputationsSparse Matrix Computations, 1976)
We consider a generalized conjugate gradient method for solvingsparse, symmetric, positive-definite systems of linear equations, principally those arising from the discretization of boundary value problems for elliptic partial differential equations. The method is based on splitting off from the original coefficient matrix a symmetric, positive-definiteonethat corresponds to a more easily solvable system of equations, and then accelerating the associated iteration using conjugate gradients. Optimality and convergence properties are presented, and the relation to other methods is discussed. Several splittings for which the method seems particularly effective are also discussed, and for some, numerical examples are given

TORUS: A step towards bridging the gap between data bases and the casual user - Mylopoulos,J.; Borgida,A.; Cohen,P.; Roussopoulos, Nick; Tsotsos,J.; Wong,H. (Information Systems, 1976)
This paper describes TORUS, a natural language understanding system that serves as a front end to a data base management system in order to facilitate communication with casual users. The system employs a semantic network to store knowledge about a data base of student files. This knowledge is used to find the meaning of each input statement, to decide what action to take with respect to the data base, and to select information that must be output in response to the input statement. A prototype version of TORUS has been implemented.

TORUS-a natural language understanding system for data management - Mylopoulos,J.; Borgida,A.; Cohen,P.; Roussopoulos, Nick; Tsotsos,J.; Wong,H. (Proceedings of the Fourth International Conference on Artificial Intelligence, 1975)

Using semantic networks for data base management - Roussopoulos, Nick; Mylopoulos,J. (Proceedings of the 1st International Conference on Very Large Data Bases, 1975)

A max {m, n} algorithm for determining the graph H from its line graph G - Roussopoulos, Nick (Information Processing Letters, 1973)