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18
Semantic data models
 ACM Computing Surveys
, 1988
"... Semantic data models have emerged from a requirement for more expressive conceptual data models. Current generation data models lack direct support for relationships, data abstraction, inheritance, constraints, unstructured objects, and the dynamic properties of an application. Although the need for ..."
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Cited by 173 (4 self)
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Semantic data models have emerged from a requirement for more expressive conceptual data models. Current generation data models lack direct support for relationships, data abstraction, inheritance, constraints, unstructured objects, and the dynamic properties of an application. Although the need for data models with richer semantics is widely recognized, no single approach has won general acceptance. This paper describes the generic properties of semantic data models and presents a representative selection of models that have been proposed since the mid1970s. In addition to explaining the features of the individual models, guidelines are offered for the comparison of models. The paper concludes with a discussion of future directions in the area of conceptual data modeling.
Efficient Checking of Temporal Integrity Constraints Using Bounded History Encoding
, 1995
"... : We present an efficient implementation method for temporal integrity constraints formulated in Past Temporal Logic. Although the constraints can refer to past states of the database, their checking does not require that the entire database history be stored. Instead, every database state is extend ..."
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Cited by 93 (6 self)
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: We present an efficient implementation method for temporal integrity constraints formulated in Past Temporal Logic. Although the constraints can refer to past states of the database, their checking does not require that the entire database history be stored. Instead, every database state is extended with auxiliary relations that contain the historical information necessary for checking constraints. Auxiliary relations can be implemented as materialized relational views. 1 Introduction Integrity constraints form an essential part of every database application. It is customary to distinguish between two kinds of constraints: static and temporal (or dynamic). Static constraints refer to the current state of the database, e.g.,"every manager is also an employee ", while temporal constraints may refer to past and future states in addition to the current state, e.g., "salaries of employees should never decrease" or "once a student drops out of the Ph.D. program, she should not be readmit...
On the Decision Problem for TwoVariable FirstOrder Logic
, 1997
"... We identify the computational complexity of the satisfiability problem for FO², the fragment of firstorder logic consisting of all relational firstorder sentences with at most two distinct variables. Although this fragment was shown to be decidable a long time ago, the computational complexity ..."
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Cited by 78 (1 self)
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We identify the computational complexity of the satisfiability problem for FO², the fragment of firstorder logic consisting of all relational firstorder sentences with at most two distinct variables. Although this fragment was shown to be decidable a long time ago, the computational complexity of its decision problem has not been pinpointed so far. In 1975 Mortimer proved that FO² has the finitemodel property, which means that if an FO²sentence is satisfiable, then it has a finite model. Moreover, Mortimer showed that every satisfiable FO²sentence has a model whose size is at most doubly exponential in the size of the sentence. In this paper, we improve Mortimer's bound by one exponential and show that every satisfiable FO²sentence has a model whose size is at most exponential in the size of the sentence. As a consequence, we establish that the satisfiability problem for FO² is NEXPTIMEcomplete.
Temporal Logic in Information Systems
 In Logics for Databases and Information Systems
, 1998
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Conceptual Modelling of Database Applications Using an Extended ER Model
, 1992
"... In this paper, we motivate and present a data model for conceptual design of structural and behavioural aspects of databases. We follow an object centered design paradigm in the spirit of semantic data models. The specification of structural aspects is divided into modelling of object structures and ..."
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Cited by 50 (9 self)
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In this paper, we motivate and present a data model for conceptual design of structural and behavioural aspects of databases. We follow an object centered design paradigm in the spirit of semantic data models. The specification of structural aspects is divided into modelling of object structures and modelling of data types used for describing object properties. The specification of object structures is based on an Extended EntityRelationship (EER) model. The specification of behavioural aspects is divided into the modelling of admissible database state evolutions by means of temporal integrity constraints and the formulation of database (trans)actions. The central link for integrating these design components is a descriptive logic based query language for the EER model. The logic part of this language is the basis for static constraints and descriptive action specifications by means of pre and postconditions. A temporal extension of this logic is the specification language for tem...
On the Feasibility of Checking Temporal Integrity Constraints
, 1995
"... We analyze the computational feasibility of checking temporal integrity constraints formulated in some sublanguages of firstorder temporal logic. Our results illustrate the impact of the quantifier pattern on the complexity of this problem. The presence of a single quantifier in the scope of a temp ..."
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Cited by 41 (6 self)
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We analyze the computational feasibility of checking temporal integrity constraints formulated in some sublanguages of firstorder temporal logic. Our results illustrate the impact of the quantifier pattern on the complexity of this problem. The presence of a single quantifier in the scope of a temporal operator makes the problem undecidable. On the other hand, if no quantifiers are in the scope of a temporal operator and all the quantifiers are universal, temporal integrity checking can be done in exponential time. 1 Introduction As temporal databases become more widely used in practice [27, 28], the need arises to address database integrity issues that are specific to such databases. In particular, it is necessary to generalize the standard notion of static integrity (involving single database states) to temporal integrity (involving sequences of database states). This work is the first attempt to date to analyze the computational feasibility of checking temporal integrity constrain...
BDDBased Decision Procedures for the Modal Logic K
 Journal of Applied Nonclassical Logics
, 2005
"... We describe BDDbased decision procedures for the modal logic K. Our approach is inspired by the automatatheoretic approach, but we avoid explicit automata construction. Instead, we compute certain fixpoints of a set of typeswhich can be viewed as an onthefly emptiness of the automaton. We use ..."
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Cited by 26 (1 self)
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We describe BDDbased decision procedures for the modal logic K. Our approach is inspired by the automatatheoretic approach, but we avoid explicit automata construction. Instead, we compute certain fixpoints of a set of typeswhich can be viewed as an onthefly emptiness of the automaton. We use BDDs to represent and manipulate such type sets, and investigate different kinds of representations as well as a "levelbased" representation scheme. The latter turns out to speed up construction and reduce memory consumption considerably. We also study the effect of formula simplification on our decision procedures. To proof the viability of our approach, we compare our approach with a representative selection of other approaches, including a translation of to QBF. Our results indicate that the BDDbased approach dominates for modally heavy formulae, while searchbased approaches dominate for propositionally heavy formulae.
An axiom system for database transactions
 Information Processing Letters 36
, 1990
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Monitoring Dynamic Integrity Constraints on Finite State Sequences and Existence Intervals
 Proc. 3rd Workshop on Foundations of Models and Languages for Data and Objects, InformatikBericht 91/3, TU Clausthal
, 1991
"... : Correct database behaviour in the course of time can be specified by requiring dynamic integrity constraints. These constraints can be expressed as temporal logic formulae which, however, usually are interpreted in infinite state sequences. Since in practice only a partial, finite prefix of an inf ..."
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Cited by 11 (5 self)
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: Correct database behaviour in the course of time can be specified by requiring dynamic integrity constraints. These constraints can be expressed as temporal logic formulae which, however, usually are interpreted in infinite state sequences. Since in practice only a partial, finite prefix of an infinite sequence is known, notions of partial admissibility of finite sequences with respect to constraints have been introduced. Admissibility can be checked on each state transition by following corresponding paths in transition graphs, which can be constructed for arbitrary temporal formulae. In this paper we modify temporal logic and transition graphs as introduced in our former work by giving them an interpretation in the empty state sequence so that the theory can be extended to complete finite sequences. Since practical dynamic constraints are to refer to database objects only during their existence intervals, this extension is utilized to handle integrity checks on the deletion of obje...
Providing timerelated constraints for conventional database systems
 In Proceedings of the 13th International Conference on VLDB
, 1987
"... A model for a historical database is described which is based upon timestamped tuples as the unit of storage. The model includes both physical and logical timestamps. The technical characteristics of writeonce laser discs prevent the use of double logical timestamps. The model distinguishes ver ..."
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Cited by 7 (0 self)
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A model for a historical database is described which is based upon timestamped tuples as the unit of storage. The model includes both physical and logical timestamps. The technical characteristics of writeonce laser discs prevent the use of double logical timestamps. The model distinguishes version from correctionupdates. It is shown that if setvalued attributes are involved the use of null values is unavoidable if backdated correctionupdates are allowed. A method of handling userdefined integrity constraint rules is outlined which involves the maintenance of a timestamped trace of such rules.