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89
The EntityRelationship Model: Toward a Unified View of Data
 ACM Transactions on Database Systems
, 1976
"... A data model, called the entityrelationship model, is proposed. This model incorporates some of the important semantic information about the real world. A special diagrammatic technique is introduced as a tool for database design. An example of database design and description using the model and th ..."
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Cited by 1509 (6 self)
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A data model, called the entityrelationship model, is proposed. This model incorporates some of the important semantic information about the real world. A special diagrammatic technique is introduced as a tool for database design. An example of database design and description using the model and the diagrammatic technique is given. Some implications for data integrity, information retrieval, and data manipulation are discussed. The entityrelationship model can be used as a basis for unification of different views of data: t,he network model, the relational model, and the entity set model. Semantic ambiguities in these models are analyzed. Possible ways to derive their views of data from the entityrelationship model are presented. Key Words and Phrases: database design, logical view of data, semantics of data, data models, entityrelationship model, relational model, Data Base Task Group, network model, entity set
Linearizability: a correctness condition for concurrent objects
, 1990
"... A concurrent object is a data object shared by concurrent processes. Linearizability is a correctness condition for concurrent objects that exploits the semantics of abstract data types. It permits a high degree of concurrency, yet it permits programmers to specify and reason about concurrent object ..."
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Cited by 977 (27 self)
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A concurrent object is a data object shared by concurrent processes. Linearizability is a correctness condition for concurrent objects that exploits the semantics of abstract data types. It permits a high degree of concurrency, yet it permits programmers to specify and reason about concurrent objects using known techniques from the sequential domain. Linearizability provides the illusion that each operation applied by concurrent processes takes effect instantaneously at some point between its invocation and its response, implying that the meaning of a concurrent object’s operations can be given by pre and postconditions. This paper defines linearizability, compares it to other correctness conditions, presents and demonstrates a method for proving the correctness of implementations, and shows how to reason about concurrent objects, given they are linearizable.
Writing Larch Interface Language Specifications
 ACM Transactions on Programming Languages and Systems
, 1987
"... Current research in specifications is emphasizing the practical use of formal specifications in program design. One way to encourage their use in practice is to provide specification languages that are accessible to both designers and programmers. With this goal in mind, the Larch family of formal s ..."
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Cited by 78 (2 self)
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Current research in specifications is emphasizing the practical use of formal specifications in program design. One way to encourage their use in practice is to provide specification languages that are accessible to both designers and programmers. With this goal in mind, the Larch family of formal specification languages has evolved to support a twotiered approach to writing specifications. This approach separates the specification of state transformations and programming language dependencies from the specification of underlying abstractions. Thus, each member of the Larch family has a subset derived from a programming language and another subset independent of any programming languages. We call the former interface languages, and the latter the Larch Shared Language. This paper focuses on Larch interface language specifications. Through examples, we illustrate some salient features of Larch/CLU, a Larch interface language for the programming language CLU. We give an example of writing an interface specification following the twotiered approach and discuss in detail issues involved in writing interface specifications and their interaction with their Shared Language components.
Categories and groupoids
, 1971
"... In 1968, when this book was written, categories had been around for 20 years and groupoids for twice as long. Category theory had by then become widely accepted as an essential tool in many parts of mathematics and a number of books on the subject had appeared, or were about to appear (e.g. [13, 22, ..."
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Cited by 47 (2 self)
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In 1968, when this book was written, categories had been around for 20 years and groupoids for twice as long. Category theory had by then become widely accepted as an essential tool in many parts of mathematics and a number of books on the subject had appeared, or were about to appear (e.g. [13, 22, 37, 58, 65] 1). By contrast, the use of groupoids was confined to a small number of pioneering articles, notably by Ehresmann [12] and Mackey [57], which were largely ignored by the mathematical community. Indeed groupoids were generally considered at that time not to be a subject for serious study. It was argued by several wellknown mathematicians that group theory sufficed for all situations where groupoids might be used, since a connected groupoid could be reduced to a group and a set. Curiously, this argument, which makes no appeal to elegance, was not applied to vector spaces: it was well known that the analogous reduction in this case is not canonical, and so is not available, when there is extra structure, even such simple structure as an endomorphism. Recently, Corfield in [41] has discussed methodological issues in mathematics with this topic, the resistance to the notion of groupoids, as a prime example. My book was intended chiefly as an attempt to reverse this general assessment of the time by presenting applications of groupoids to group theory
Experiential and Formal Models of Geographic Space
 B
, 1995
"... This paper is concerned not with space and spatial relations as objective entities of the world, but rather with human experience and perception of phenomena and relations in space. The goal arising from this concern is to identify models of space that can be used both in cognitive science and in th ..."
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Cited by 38 (5 self)
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This paper is concerned not with space and spatial relations as objective entities of the world, but rather with human experience and perception of phenomena and relations in space. The goal arising from this concern is to identify models of space that can be used both in cognitive science and in the design and implementation of geographic information systems (GISs). Experiential models of the world are based on sensorimotor and visual experiences with environments, and form in individual minds as the associated bodies and senses experience their worlds. Formal models consist of axioms expressed in a formal language, together with mathematical rules to infer conclusions from them. The paper reviews both kinds of models, viewing them each as abstractions of the same 'real world.' The review of experiential models is grounded in recent developments in cognitive science, expounded by Rosch, Johnson, Talmy, and especially Lakoff. Among other things, these models suggest that perception and...
ObjectOriented Modeling for GIS
, 1992
"... The data model upon which most of today's commercial database management systems are based has shown to be insufficient for geographic information systems (GISs). The recently promoted objectoriented model provides some useful tools for data abstraction and data structuring, which augment the ..."
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Cited by 35 (8 self)
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The data model upon which most of today's commercial database management systems are based has shown to be insufficient for geographic information systems (GISs). The recently promoted objectoriented model provides some useful tools for data abstraction and data structuring, which augment the conventional tools and overcomes some deficiencies inherent to the traditional relational model. In particular, the concepts of complex objects with pertinent operations are more powerful modeling methods than the currently popular structure of relational tables and relational algebra. This survey article presents the concepts of objectoriented modeling applied to geographic data and demonstrates their impact on future GISs.
Propositional information system
, 1996
"... Resolution is an often used method for deduction in propositional logic. Here a proper organization of deduction is proposed which avoids redundant computations. It is based on a generic framework of decompositions and local computations as introduced by Shenoy, Shafer [29]. The system contains the ..."
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Cited by 29 (15 self)
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Resolution is an often used method for deduction in propositional logic. Here a proper organization of deduction is proposed which avoids redundant computations. It is based on a generic framework of decompositions and local computations as introduced by Shenoy, Shafer [29]. The system contains the two basic operations with information, namely marginalization (or projection) and combination; the latter being an idempotent operation in the present case. The theory permits the conception of an architecture of distributed computing. As an important application assumptionbased reasoning is discussed. 1
Dynamic Algebras: Examples, Constructions, Applications
 Studia Logica
, 1991
"... Dynamic algebras combine the classes of Boolean (B 0 0) and regular (R [ ; ) algebras into a single finitely axiomatized variety (B R 3) resembling an Rmodule with "scalar" multiplication 3. The basic result is that is reflexive transitive closure, contrary to the intuition tha ..."
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Cited by 19 (1 self)
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Dynamic algebras combine the classes of Boolean (B 0 0) and regular (R [ ; ) algebras into a single finitely axiomatized variety (B R 3) resembling an Rmodule with "scalar" multiplication 3. The basic result is that is reflexive transitive closure, contrary to the intuition that this concept should require quantifiers for its definition. Using this result we give several examples of dynamic algebras arising naturally in connection with additive functions, binary relations, state trajectories, languages, and flowcharts. The main result is that free dynamic algebras are residually finite (i.e. factor as a subdirect product of finite dynamic algebras), important because finite separable dynamic algebras are isomorphic to Kripke structures. Applications include a new completeness proof for the Segerberg axiomatization of propositional dynamic logic, and yet another notion of regular algebra. Key words: Dynamic algebra, logic, program verification, regular algebra. This paper or...
The Cryptographic Impact of Groups with Infeasible Inversion
 MASTER’S THESIS, MIT
, 2003
"... Algebraic group structure is an important  and often overlooked  tool for constructing and comparing cryptographic applications. Our driving example is the open problem of finding provably secure transitive signature schemes for directed graphs, proposed by Micali and Rivest [41]. A directed trans ..."
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Cited by 19 (1 self)
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Algebraic group structure is an important  and often overlooked  tool for constructing and comparing cryptographic applications. Our driving example is the open problem of finding provably secure transitive signature schemes for directed graphs, proposed by Micali and Rivest [41]. A directed transitive signature scheme (DTS) allows Alice to sign a subset of edges on a directed graph in such a way that anyone can compose Alice's signatures on ab and bc to obtain her signature on edge ac. We formalize the necessary mathematical criteria for a secure DTS scheme when the signatures can be composed in any order, showing that the edge signatures in such a scheme form a special (and powerful) mathematical group not known to exist: an Abelian trapdoor group with infeasible inversion (ATGII). Furthermore, we show that such a DTS scheme is more complex  in a blackbox sense  than standard signatures, public key encryption and oblivious transfer. To our knowledge, this is the first separation between standard signature schemes and any of the many variant signature schemes proposed. We formalize