Showing papers in "ACM Computing Surveys in 1987"
TL;DR: This paper provides a tutorial introduction to the primary components of semantic models, which are the explicit representation of objects, attributes of and relationships among objects, type constructors for building complex types, ISA relationships, and derived schema components.
Abstract: Most common database management systems represent information in a simple record-based format. Semantic modeling provides richer data structuring capabilities for database applications. In particular, research in this area has articulated a number of constructs that provide mechanisms for representing structurally complex interrelations among data typically arising in commercial applications. In general terms, semantic modeling complements work on knowledge representation (in artificial intelligence) and on the new generation of database models based on the object-oriented paradigm of programming languages.This paper presents an in-depth discussion of semantic data modeling. It reviews the philosophical motivations of semantic models, including the need for high-level modeling abstractions and the reduction of semantic overloading of data type constructors. It then provides a tutorial introduction to the primary components of semantic models, which are the explicit representation of objects, attributes of and relationships among objects, type constructors for building complex types, ISA relationships, and derived schema components. Next, a survey of the prominent semantic models in the literature is presented. Further, since a broad area of research has developed around semantic modeling, a number of related topics based on these models are discussed, including data languages, graphical interfaces, theoretical investigations, and physical implementation strategies.
1,236 citations
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TL;DR: A variety of data compression methods are surveyed, from the work of Shannon, Fano, and Huffman in the late 1940s to a technique developed in 1986, which has important application in the areas of file storage and distributed systems.
Abstract: This paper surveys a variety of data compression methods spanning almost 40 years of research, from the work of Shannon, Fano, and Huffman in the late 1940s to a technique developed in 1986. The aim of data compression is to reduce redundancy in stored or communicated data, thus increasing effective data density. Data compression has important application in the areas of file storage and distributed systems. Concepts from information theory as they relate to the goals and evaluation of data compression methods are discussed briefly. A framework for evaluation and comparison of methods is constructed and applied to the algorithms presented. Comparisons of both theoretical and empirical natures are reported, and possibilities for future research are suggested.
581 citations
TL;DR: There are areas of programming language research—modules, polymorphism, persistence, and inheritance—that must be developed and applied to achieve the goal of a useful and consistent database programming language.
Abstract: Traditionally, the interface between a programming language and a database has either been through a set of relatively low-level subroutine calls, or it has required some form of embedding of one language in another. Recently, the necessity of integrating database and programming language techniques has received some long-overdue recognition. In response, a number of attempts have been made to construct programming languages with completely integrated database management systems. These languages, which we term database programming languages, are the subject of this review.The design of these languages is still in its infancy, and the purpose of writing this review is to identify the areas in which further research is required. In particular, we focus on the problems of providing a uniform type system and mechanisms for data to persist. Of particular importance in solving these problems are issues of polymorphism, type inheritance, object identity, and the choice of structures to represent sets of similar values. Our conclusion is that there are areas of programming language research—modules, polymorphism, persistence, and inheritance—that must be developed and applied to achieve the goal of a useful and consistent database programming language. Other research areas of equal importance, such as implementation, transaction handling, and concurrency, are not examined here in any detail.
384 citations
TL;DR: Using the IS research framework suggested by Ives, Hamilton, and Davis, research into IS problems is classified into several perspectives whose relevance in coping with the problems is discussed.
Abstract: The paper puts information systems (IS) research dealing with IS problems into perspective. IS problems are surveyed and classified. Using the IS research framework suggested by Ives, Hamilton, and Davis, research into IS problems is classified into several perspectives whose relevance in coping with the problems is discussed. Research perspectives focusing on IS operations environment, IS development process, IS development organization, IS development methods, and IS theories are distinguished. The paper concludes with suggestions for future research and how to deal with IS problems in practice.
334 citations
TL;DR: A uniform model in which published algorithms can be cast is given, and the fundamental principles on which distributed deadlock detection schemes are based are presented, and a hierarchy of deadlock models is presented.
Abstract: The problem of deadlock detection in distributed systems has undergone extensive study. An important application relates to distributed database systems. A uniform model in which published algorithms can be cast is given, and the fundamental principles on which distributed deadlock detection schemes are based are presented. These principles represent mechanisms for developing distributed algorithms in general and deadlock detection schemes in particular. In addition, a hierarchy of deadlock models is presented; each model is characterized by the restrictions that are imposed upon the form resource requests can assume. The hierarchy includes the well-known models of resource and communication deadlock. Algorithms are classified according to both the underlying principles and the generality of resource requests they permit. A number of algorithms are discussed in detail, and their complexity in terms of the number of messages employed is compared. The point is made that correctness proofs for such algorithms using operational arguments are cumbersome and error prone and, therefore, that only completely formal proofs are sufficient for demonstrating correctness.
268 citations
TL;DR: This paper reviews empirical studies concerning the readability of text from computer screens and focuses on the form and physical attributes of complex, realistic displays of text material.
Abstract: This paper reviews empirical studies concerning the readability of text from computer screens. The review focuses on the form and physical attributes of complex, realistic displays of text material. Most studies comparing paper and computer screen readability show that screens are less readable than paper. There are many factors that could affect the readability of computer screens. The factors explored in this review are the features of characters, the formatting of the screen, the contrast and color of the characters and background, and dynamic aspects of the screen. Numerous areas for future research are pinpointed.
266 citations
TL;DR: The data-modeling and computational requirements for integrated computer aided manufacturing (CAM) databases are analyzed, and the most common representation schemes for modeling solid geometric objects in a computer are described.
Abstract: The data-modeling and computational requirements for integrated computer aided manufacturing (CAM) databases are analyzed, and the most common representation schemes for modeling solid geometric objects in a computer are described. The primitive instancing model, the boundary representation, and the constructive solid geometry model are presented from the viewpoint of database representation. Depending on the representation scheme, one can apply geometric transformations to the stored geometric objects. The standard transformations, scaling, translation, and rotation, are outlined with respect to the data structure aspects. Some of the more recent developments in the area of engineering databases with regard to supporting these representation schemes are then explored, and a classification scheme for technical database management systems is presented that distinguishes the systems according to their level of object orientation: structural or behavioral object orientation. First, several systems that are extensions to the relational model are surveyed, then the functional data model DAPLEX, the nonnormalized relational model NF2, and the database system R2D2 that provides abstract data types in the NF2 model are described.
116 citations