User interface strategies '88 (videotape) - Shneiderman, Ben; Malone,Thomas; Norman,Donald; Foley,James (University of Maryland at College Park, 1988)

Algorithms for covering and packing and applications to CAD/CAM (abstract only): preliminary results - Mount, Dave; Silverman,Ruth (Proceedings of the 15th annual conference on Computer Science, 1987)
Computational geometry deals with the computational complexity of geometric problems within the framework of the analysis of algorithms. Numerous applications have been found to computer graphics, computer-aided design, pattern recognition and robotics.Among the geometric problems are bin packing problems. C.A. Roger “Packing and Covering”, Cambridge University Press (1964) studied these problems. Many of these are hard problems, and very few have been solved. Some packing problems are the restriction of a very interesting problem in CAM (computer-aided manufacture). In the manufacture of clothing, certain parts, such as sleeves, are laid out as repeated polygonal copies and combinations on a bolt of cloth. This pattern layout is traditionally (and currently) done by hand. It's a candidate for automation. We propose some special cases of this problem whose solution can be extended to practical use. We are working on several geometric questions involving packing translations of objects. Classical results in mathematics demonstrate equivalence between certain packing problems and finding optimal enclosed figures. J. O'Rourke et al [“An optimal algorithm for finding minimal enclosing triangles”, J. of Algorithms 7, 258-264 (1986)], as well as V. Klee and M. Laskowski [“Finding the smallest triangles containing a given convex polygon”, J. of Algorithms 6, 359-375 (1985)] have produced algorithms for finding a smallest area triangle containing (or enclosing) a given polygon. Smallest area convex polygons of a certain type, containing a given set, can be viewed as larger pieces of fabric containing pattern to be cut out. We have an optimal algorithm for finding largest enclosed polygons for a given set. We also have preliminary results for smallest enclosing polygons. These results have theoretical interest, and have applications to robotics and collision avoidance, as well as to manufacture.

Computer-supported cooperative work (panel): is this REALLY a new field of research? - Greif,Irene; Curtis,Bill; Krasner,Herb; Malone,Thomas W.; Shneiderman, Ben (Proceedings of the SIGCHI/GI conference on Human factors in computing systems and graphics interface, 1987)

The decomposition of a square into rectangles of minimal perimeter - Kong,T.Y; Mount, Dave; Werman,Michael (Discrete Applied Mathematics, 1987)
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.

THE DISCRETE GEODESIC PROBLEM - JOSEPH,SB; Mount, Dave; Papadimitriou,C. H (SIAM Journal on Computing (SICOMP), 1987)
We presentan algorithm for determining the shortest path between a source and a destinationon an arbitrary (possibly nonconvex) polyhedralsurface. The path is constrained to lie on the surface, and distances are measured according to the Euclidean metric. Our algorithm runs in time O(n log n) and requires O(n2) space, where n is the number of edges of the surface. After we run our algorithm, the distance from the source to any other destination may be determined using standard techniques in time O(log n) by locating the destination in the subdivision created by the algorithm. The actual shortest path from the source to a destination can bereported in time O(k+log n), where k is the number of faces crossed by the path. The algorithm generalizes to the case of multiple source points to build the Voronoi diagram on the surface, where n is now the maximum of the number of vertices and the number of sources.

Life on a desert island - Drapkin,J.; Miller,M.; Perlis, Don (Proc. Workshop on The Frame Problem in Artificial Intelligence, 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

An output sensitive algorithm for computing visibility graphs - Ghosh,Subir Kumar; Mount, Dave (Foundations of Computer Science, 1987., 28th Annual Symposium on, 1987)
The visibility graph of a set of nonintersecting polygonal obstacles in the plane is an undirected graph whose vertices are the vertices of the obstacles and whose edges are pairs of vertices (u, v) such that the open line segment between u and v does not intersect any of the obstacles. The visibility graph is an important combinatorial structure in computational geometry and is used in applications such as solving visibility problems and computing shortest paths. An algorithm is presented that computes the visibility graph of s set of obstacles in time O(E + n log n), where E is the number of edges in the visibility graph and n is the total number of vertices in all the obstacles.

Proving self-utterances - Miller,M.; Perlis, Don (Journal of Automated Reasoning, 1987)

Sequence similarity - Mount, Stephen M. (Nature, 1987)

Shared memory algorithms and the medial axis transform - Chandran,S.; Mount, Dave (IEEE Workshop on Computer Architecture for PAMI, 1987)

Storing the subdivision of a polyhedral surface - Mount, Dave (Discrete & Computational Geometry, 1987)
A common structure arising in computational geometry is the subdivision of a plane defined by the faces of a straight-line planar graph. We consider a natural generalization of this structure on a polyhedral surface. The regions of the subdivision are bounded by geodesics on the surface of the polyhedron. A method is given for representing such a subdivision that is efficient both with respect to space and the time required to answer a number of different queries involving the subdivision. For example, given a pointx on the surface of the polyhedron, the region of the subdivision containingx can be determined in logarithmic time. Ifn denotes the number of edges in the polyhedron,m denotes the number of geodesics in the subdivision, andK denotes the number of intersections between edges and geodesics, then the space required by the data structure isO((n +m) log(n +m)), and the structure can be built inO(K + (n +m) log(n +m)) time. Combined with existing algorithms for computing Voronoi diagrams on the surface of polyhedra, this structure provides an efficient solution to the nearest-neighbor query problem on polyhedral surfaces.

TIME PERTURBATION ANALYSIS FOR THE MOS SYSTEM - Gaitan,Michael; Mayergoyz, Issak D (COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 1987)
The development of a numerical implementation of the small signal response of the MOS (Metal-Oxide-Silicon) capacitor using time perturbation analysis is discussed. The effects of nonconstant doping profiles and interface and bulk traps are included. The model uses Fermi-Dirac statistics to describe the occupancy of the interface and bulk traps. The oxide region is considered to have no mobile carriers and any fixed oxide charge distribution is modeled as a charge sheet at the Si-SiO2 interface. This technique can be used to find the small signal response of the device from the static solution.

Completeness results for circumscription - Perlis, Don; Minker, Jack (Artificial Intelligence, 1986)
We investigate the model theory of the notion of circumscription, and find completeness theorems that provide a partial converse to a result of McCarthy. We show that the circumscriptive theorems are precisely the truths of the minimal models, in the case of various classes of theories, and for various versions of circumscription. We also present an example of commonsense reasoning in which first-order circumscription does not achieve the intuitive and desired minimization.

Design and research on the interactive encyclopedia system (TIES) - Morariu,J.; Shneiderman, Ben (Proc. 29th Conference of the Association for the Development of Computer Based Instructional Systems, 1986)
Printed books were an enormous stimulus to science, culture, commerce, and entertainment. Electronic books and hypertext systems may produce a similar stimulus in the next century, but current designs are poor. Typical screens are too small, too slow, too complicated, and too hard to read. With careful attention to the user interface and the underlying technology, we have a chance to create a new medium that is potentially more attractive and effective than printed books in many situations.

An experimental comparison of a mouse and arrow-jump keys for an interactive encyclopedia - Ewing,John; Mehrabanzad,Simin; Sheck,Scott; Ostroff,Dan; Shneiderman, Ben (International Journal of Man-Machine Studies, 1986)
This paper reports on an experiment which was conducted to examine relative merits of using a mouse or arrow-jump keys to select text in an interactive encyclopedia. Timed path traversais were performed by subjects using each device, and were followed by subjective questions. Personality and background of the subjects were recorded to see if those attributes would affect device preference and performance. The arrow-jump keys were found to have the quickest traversal times for paths with either short or long target distances. The subjective responses indicated that the arrow-jump method was overwhelmingly preferred over the mouse method. Personality type was not found to play a critical role.

Learning Disabled Students' Difficulties in Learning to Use A Word Processor: Implications for Instruction and Software Evaluation - MacArthur,Charles A.; Shneiderman, Ben (Journal of Learning DisabilitiesJ Learn Disabil, 1986)
Learning disabled (LD) students can derive great benefits from using word processors. The ability to produce a neat, printed copy can increase motivation and encourage writing for a wider audience. The editing power makes revision possible without tedious recopying, thus freeing students and teachers to approach writing as a process involving repeated drafts. Specific problems with handwriting and spelling can also be circumvented. However, learning to use a word processor often presents problems. Based on a study of LD students learning to use word processing, this paper makes recommendations for evaluating word processing software and designing instruction that is sensitive to students difficulties.

Learning disabled students' difficulties in learning to use a word processor: implications for design - MacArthur,Charles A.; Shneiderman, Ben (ACM SIGCHI Bulletin, 1986)
Learning disabled students can derive great benefits from using work processors. The ability to produce a neat, printed copy can increase motivation and encourage writing for a wider audience. The editing power makes revision possible without tedious re-copying, thus freeing students and teachers to approach writing as a process involving repeated drafts. Specific problems with handwriting and spelling can also be circumvented. However, learning to use the editing capabilities often presents problems for students, especially those with learning difficulties. Word processors must be designed that are simple, easy to learn, and yet powerful. This study makes software design recommendations based on a study of learning disabled students learning to use word processing.Two groups of four LD students (4th-6th grade) were given twelve hours of word processing instruction using two word processors. Detailed records of progess and errors were made during learning and a final assessment task. Specific design problems are reported and recommendations are made for tasks such as cursor movement, insertion/deletion, use of nulls, blanks, and formatting characters, and overall organization.

Parallel ear decomposition search (EDS) and st-numbering in graphs - Maon,Y.; Schieber,B.; Vishkin, Uzi (Theoretical Computer Science, 1986)

A Parallel Self-Modifying Default Reasoning System - Minker, Jack; Perlis, Don; Subramanian,K. (AAAI, 1986)

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.

Computing protected circumscription - Minker, Jack; Perlis, Don (The Journal of Logic Programming, 1985)

The Engineering of an Environment on Small Machines - Zelkowitz, Marvin V; Elgot,J.; Itkin,D.; Kowalchack,B.; Maggio,M. (Proceedings of the IEEE 1st International Conference on Computer Workstations, 1985)

On Finding Shortest Paths on Convex Polyhedra. - Mount, Dave (CENTER FOR AUTOMATION RESEARCH, UNIVERSITY OF MARYLAND COLLEGE PARK, 1985)
Applications in robotics and autonomous navigation have motivated the study of motion planning and obstacle avoidance algorithms. The special case considered here is that of moving a point (the object) along the surface of a convex polyhedron (the obstacle) with n vertices. Sharir and Schorr have developed an algorithm that, given a source point on the surface of a convex polyhedron, determines the shortest path from the source to any point on the polyhedron in linear time after O(n cubed log n) preprocessing time. The preprocessed output requires O(n squared) space. By using known algorithms for fast planar point location, the shortest path query time for Sharir and Schorr's algorithm is shown to be O(k + log n) where k is the number faces traversed by the path. We give an improved preprocessing algorithm that runs in O(n squared log n) time requiring the same query time and space. We also show how to store the output of the preprocessing algorithm in O(n log n) space while maintaining the same query time. (Author)
Keywords: *ALGORITHMS; *POLYGONS; *Polyhedrons; *PREPROCESSING; AUTONOMOUS NAVIGATION; AVOIDANCE.; BARRIERS; INTERROGATION; MOTION; output; PATHS; PE61102F; planning; POSITION(LOCATION); ROBOTICS; THEORETICAL MATHEMATICS; TIME

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

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

Voronoi Diagrams on the Surface of a Polyhedron. - Mount, Dave (CENTER FOR AUTOMATION RESEARCH, UNIVERSITY OF MARYLAND COLLEGE PARK, 1985)
This document presents an algorithm that computes the Voronol diagram of a set of point lying on the surface of a possibly nonconvex polyhedron. Distances are measured in the Euclidean metric along the surface of the polyhedron. The algorithm runs in O(n squared log n) time and requires O(n squared) space to store the final data structure, where n is the maximum of the number of edges and source points on the polyhedron. This algorithm generalizes or improves the running times of a number of shortest path problems both on polyhedra and in the plane amidst polygonal obstacles. By applying standard algorithms for point location, we can determine the distance from a query point to the nearest source in O(log n) time and can list the shortest path in O(k + log n) time, where k is the number of faces traversed by the path. The algorithm achieves its efficiency by a novel method of searching the polyhedron's surface. (Author)
Keywords: *POLYGONS; *Polyhedrons; algorithms; DIAGRAMS.; EDGES; INTERROGATION; PATHS; PE61102F; POSITION(LOCATION); SURFACES; THEORETICAL MATHEMATICS; WUAFOSR2304A7

Applications or Protected Circumscription - Minter,J.; Perlis, Don (7th International Conference on Automated Deduction, Napa, California, USA, May 14-16, 1984: proceedings, 1984)

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

Protected circumscription - Minker, Jack; Perlis, Don (Proc. Workshop on Non-Monotonic Reasoning, 1984)

Randomized and deterministic simulations of PRAMs by parallel machines with restricted granularity of parallel memories - Mehlhorn,K.; Vishkin, Uzi (Acta Informatica, 1984)

RNA splicing and the involvement of small ribonucleoproteins - Mount, Stephen M.; Steitz,J. A. (Modern cell biology, 1984)
Keywords: Article synthèse; Articulo sintesis; review; Ribonucleoprotein; Ribonucleoproteina; Ribonucléoprotéine; RNA; Sn-RNA; splicing

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

An empirical comparison of two PLATO text editors. - Shneiderman, Ben; Hill,R.; Jacob,R.; Mah,W. (Journal of Computer-Based Instruction, 1983)
Two PLATO system text editors were evaluated with 14 nonprogrammers and 14 programmers who were either university staff or college students. Half of each group learned the "plain" editor, which had 8 commands and 3 screens of HELP material; while the other half of each group learned the "fancy" editor, which had 15 commands and 1 screen of HELP material. The fancy editor is a subset of the widely used TUTOR editor, but nonprogrammers preferred the plain editor. Faster learning, faster performance, fewer invocations of HELP material, and fewer requests for human assistance were characteristic of the plain editor.

Program indentation and comprehensibility - Miara,Richard J.; Musselman,Joyce A.; Navarro,Juan A.; Shneiderman, Ben (Communications of the ACM, 1983)
Keywords: indentation; program format; program readability

Pseudogenes for human small nuclear RNA U3 appear to arise by integration of self-primed reverse transcripts of the RNA into new chromosomal sites - Bernstein,L B; Mount, Stephen M.; Weiner,A M (CellCell, 1983)
We find that both human and rat U3 snRNA can function as self-priming templates for AMV reverse transcriptase in vitro. The 74 base cDNA is primed by the 3' end of intact U3 snRNA, and spans the characteristically truncated 69 or 70 base U3 sequence found in four different human U3 pseudogenes. The ability of human and rat U3 snRNA to self-prime is consistent with a U3 secondary structure model derived by a comparison between rat U3 snRNA and the homologous D2 snRNA from Dictyostelium discoideum. We propose that U3 pseudogenes are generated in vivo by integration of a self-primed cDNA copy of U3 snRNA at new chromosomal sites. We also consider the possibility that the same cDNA mediates gene conversion at the 5' end of bona fide U3 genes where, over the entire region spanned by the U3 cDNA, the two rat U3 sequence variants U3A and U3B are identical.
Keywords: Animals; Base Sequence; DNA; genes; HUMANS; Nucleic Acid Conformation; Rats; Recombination, Genetic; Repetitive Sequences, Nucleic Acid; RNA; RNA, Small Nuclear; RNA-Directed DNA Polymerase; Templates, Genetic; Transcription, Genetic

RNA processing: Lessons from mutant globins - Mount, Stephen M.; Steitz,Joan (Nature, 1983)

RNA processing: Sequences that signal where to splice - Mount, Stephen M. (Nature, 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

Splicing of messenger RNA precursors is inhibited by antisera to small nuclear ribonucleoprotein - Padgett,Richard A.; Mount, Stephen M.; Steitz,Joan A.; Sharp,Phillip A. (Cell, 1983)

The U1 small nuclear RNA-protein complex selectively binds a 5′ splice site in vitro - Mount, Stephen M.; Pettersson,Ingvar; Hinterberger,Monique; Karmas,Aavo; Steitz,Joan A. (Cell, 1983)
The ability of purified U1 small nuclear RNA-protein complexes (U1 snRNPs) to bind in vitro to two RNAs transcribed from recombinant DNA clones by bacteriophage T7 RNA polymerase has been studied. A transcript which contains sequences corresponding to the small intron and flanking exons of the major mouse beta-globin gene is bound in marked preference to an RNA devoid of splice site sequences. The site of U1 snRNP binding to the globin RNA has been defined by T1 ribonuclease digestion of the RNA-U1 snRNP complex. A 15-17-nucleotide region, including the 5' splice site, remains undigested and complexed with the snRNP such that it can be co-precipitated by antibodies directed against the U1 snRNP. Partial proteinase K digestion of the U1 snRNP abolishes interaction with the globin RNA, indicating that the snRNP proteins contribute significantly to RNA binding. No RNA cleavage, splicing, or recognition of the 3' splice site by U1 snRNPs has been detected. Our results are discussed in terms of the probable role of U1 snRNPs in the messenger RNA splicing of eucaryotic cell nuclei.

A catalogue of splice junction sequences - Mount, Stephen M. (Nucleic Acids ResearchNucl. Acids Res., 1982)
Splice junction sequences from a large number of nuclear and viral genes encoding protein have been collected. The sequence ACAG/GTGAAGT was found to be a consensus of 139 exon-intron boundaries (or donor sequences) and (CT)nNTCAG/G was found to be a consensus of 130 intron-exon boundaries (or acceptor sequences). The possible role of splice junction sequences as signals for processing is discussed.

Isomorphism of graphs with bounded eigenvalue multiplicity - Babai,László; Grigoryev,D. Yu.; Mount, Dave (Proceedings of the fourteenth annual ACM symposium on Theory of computing, 1982)
We investigate the connection between the spectrum of a graph, i.e. the eigenvalues of the adjacency matrix, and the complexity of testing isomorphism. In particular we describe two polynomial time algorithms which test isomorphism of undirected graphs whose eigenvalues have bounded multiplicity. If X and Y are graphs of eigenvalue multiplicity m, then the isomorphism of X and Y can be tested by an O(n4m+c) deterministic and by an O(n2m+c) Las Vegas algorithm, where n is the number of vertices of X and Y.

Structure and function of small ribonucleoproteins from eukaryotic cells - Steitz,J. A.; Berg,C; Gottlieb,E.; Hardin,J A; Hashimoto,C; Hendrick,J P; Hinterberger,M.; Krikeles,M; Lerner,M R; Mount, Stephen M. (Princess Takamatsu symposiaInt. Symp. Princess Takamatsu Cancer Res. Fund, 1982)
Autoantibodies from patients with systemic lupus erythematosus and other related diseases have been used to identify and study small RNA-protein complexes from mammalian cells. Properties of three previously described and several new classes of small ribonucleoproteins (RNPs) are reviewed. The sequence of Drosophila U1 RNA reveals that the region proposed to pair with 5' splice junctions is conserved, while that proposed to interact with 3' junctions diverges; this forces some revision of the model for U1 small nuclear (sn)RNP participation in hnRNA splicing. Further characterization of the Ro and La small RNPs has shown that the Ro small cytoplasmic (sc)RNPs are a subclass of La RNPs. Both tRNA and 5S rRNA precursors are at least transiently associated with the La protein. This raises the possibility that the La protein may be an RNA polymerase III transcription factor.
Keywords: Antigen-Antibody Complex; Autoantibodies; HUMANS; Lupus Erythematosus, Systemic; Nucleoproteins; Ribonucleoproteins; RNA Polymerase III; Transcription, Genetic

Sequence of U1 RNA from Drosophila melanogaster: implications for U1 secondary structure and possible involvement in splicing - Mount, Stephen M.; Steitz,Joan A. (Nucleic Acids ResearchNucl. Acids Res., 1981)
U1 RNA from cultured Drosophila melanogaster cells (Kc) was identified by its ability to be recognized, as an RNP, by anti-(U1)RNP antibodies from human lupus patients. Its sequence was deduced largely from direct analysis of the RNA molecule and then confirmed by DNA sequence determinations on a genomic clone isolated by hybridization to Drosophila U1 RNA. The Drosophila U1 RNA sequence exhibits 72% agreement with human U1 RNA. Nucleotides 3-11, which are complementary to the entire consensus sequence for donor (5′) splice junctions in hnRNA, and to part of the acceptor (3′) consensus, are exactly conserved. However, nucleotides 14-21, postulated to interact only with acceptor junctions, differ. Comparison of the Drosophila U1 sequence with vertebrate U1 sequences allows a particular secondary structure model to be preferred over others. These results are consistent with the hypothesis that U1 snRNPs are involved in splicing, but suggest specific modifications of the model detailing molecular interactions between U1 RNA and hnRNA during the splicing reaction.

Transcription of cloned tRNA and 5S RNA genes in a Drosophila cell free extract - Dingermann,Theodor; Sharp,Stephen; Appel,Bernd; DeFranco,Donald; Mount, Stephen M.; Heiermann,Reinhard; Pongs,Olaf; Söll,Dieter (Nucleic Acids ResearchNucl. Acids Res., 1981)
We describe the preparation of a cell-free extract from Drosophila Kc cells which allows transcription of a variety of cloned eukaryotic RNA polymerase III genes. The extract has low RNA-processing nuclease activity and thus the major products obtained are primary transcripts.

Are snRNPs involved in splicing? - Lerner,Michael R.; Boyle,John A.; Mount, Stephen M.; Wolin,Sandra L.; Steitz,Joan A. (Nature, 1980)
Discrete, stable small RNA molecules are found in the nuclei of cells from a wide variety of eukaryotic organisms. Many of these small nuclear RNA (snRNA) species, which range in size from about 90 to 220 nucleotides, have been well-characterised biochemically, and some sequenced. However, their function has remained obscure. The most abundant snRNA species exist as a closely related set of RNA–protein complexes called small nuclear ribonucleoproteins (snRNPs). snRNPs are the antigens recognised by antibodies from some patients with lupus erythematosus (LE), an autoimmune rheumatic disease. Anti-RNP antibodies from lupus sera selectively precipitate snRNP species containing Ula7 and Ulb9 RNAs from mouse Ehrlich ascites cell nuclei, whereas anti-Sm antibodies bind these snRNPs and four others containing U2, U4, US and U6 RNAs. Both antibody systems precipitate the same seven prominent nuclear proteins (molecular weight 12,000–32,000). All molecules of the snRNAs U1, U2, U4, U5 and U6 appear to exist in the form of antigenic snRNPs9. The particles sediment at about 10S and each probably contains a single snRNA molecule. Indirect immunofluorescence studies using anti-RNP and anti-Sm sera confirm the nuclear (but non-nucleolar) location of the antigenic snRNPs. Here we present several lines of evidence that suggest a direct involvement of snRNPs in the splicing of hnRNA. Most intriguing is the observation that the nucleotide sequence at the 5′ end of U1 RNA exhibits extensive complementarity to those across splice junctions in hnRNA molecules.

Syntactic/semantic interactions in programmer behavior: A model and experimental results - Shneiderman, Ben; Mayer,Richard (International Journal of Parallel Programming, 1979)
This paper presents a cognitive framework for describing behaviors involved in program composition, comprehension, debugging, modification, and the acquisition of new programming concepts, skills, and knowledge. An information processing model is presented which includes a long-term store of semantic and syntactic knowledge, and a working memory in which problem solutions are constructed. New experimental evidence is presented to support the model of syntactic/semantic interaction.

A guide to major job accounting systems: the Logger system of the UNIVAC 1100 series operating system - Mohr,Jeffrey Myron; Agrawala, Ashok K.; Flannagan,J. F. (U.S. Dept. of Commerce, National Bureau of Standards : for sale by the Supt. of Docs., U.S. Govt. Print. Off., 1978)
Keywords: Accounting; Business & Economics / Accounting / General; Electronic digital computers; EXEC 8 (Electronic computer system); Reference / Questions & Answers; Univac 1100 series (Computer); Univac computer

Experimental investigations of the utility of detailed flowcharts in programming - Shneiderman, Ben; Mayer,Richard; McKay,Don; Heller,Peter (Communications of the ACM, 1977)
This paper describes previous research on flowcharts and a series of controlled experiments to test the utility of detailed flowcharts as an aid to program composition, comprehension, debugging, and modification. No statistically significant difference between flowchart and nonflowchart groups has been shown, thereby calling into question the utility of detailed flowcharting. A program of further research is suggested.
Keywords: Debugging; experimental testing; flowcharts; human factors; modification; program composition; program comprehension

The relationship between the pattern recognition problem and the workload characterization problem - Agrawala, Ashok K.; Mohr,J. M (1977 CMG Conference, 1977)

Utility Functions, Public Goods, and Income Redistribution - Mann,Arthur J.; Perlis, Don (Public Finance Review, 1977)
The results of fiscal incidence studies depend upon the underlying utility functions pertinent to the distribution of public good benefits among income classes. Generally, the use of such functions is not explicitly recognized. By taking, in the first instance, an extended approach to utility based on an original Aaron-McGuire formulation and, in the second instance, a new approach, it is concluded that the income-equalizing tendencies of fiscal activities may be overstated when more conventional analysis is employed.

Error checking with pointer variables - Zelkowitz, Marvin V; McMullin,Paul R.; Merkel,Keith R.; Larsen,Howard J. (Proceedings of the 1976 annual conference, 1976)
The use of pointer variables in a programming language often results in a difficult class of errors to detect. Pointers may point to storage that no longer is allocated, or storage may be allocated as one data type and accessed as another. This report describes the implementation of pointers in the PLUM PL/1 compiler such that all error conditions are detected. In addition, preliminary tests with PLUM seem to indicate that the total checking of pointers is not as expensive an operation as it first appears.

The EXEC-8 Log System: Error Analysis - Mohr,J. M; Agrawala, Ashok K.; Flanagan,J. F.; Science,University of Maryland. Dept. of Computer (University of Maryland, Dept. of Computer Science, 1976)

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)