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The COCOON Object Model
, 1994
"... The COCOON model was intended to extend the concepts of relational database management systems (DBMSs) beyond nested relational to objectoriented ones. Key characteristics of COCOON and its database language COOL are: generic, setoriented query and update operators similar to relational algebra an ..."
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Cited by 59 (21 self)
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The COCOON model was intended to extend the concepts of relational database management systems (DBMSs) beyond nested relational to objectoriented ones. Key characteristics of COCOON and its database language COOL are: generic, setoriented query and update operators similar to relational algebra and SQL updates, respectively; objectpreserving semantics of query operators, which allows for the definition of updatable views; update operations that keep modelinherent integrity constraints consistent; a separation of the two aspects of programming language "classes": type vs. collection; predicative description of collections, similar to "defined concepts" in KLOnelike knowledge representation languages; automatic classification of objects and views (positioning in the class hierarchy). This report gives a comprehensive introduction to the COCOON model and its language COOL as well as a formal definition. Our formalization uses denotational semantics, a popular technique in programming...
Computing With FirstOrder Logic
, 1995
"... We study two important extensions of firstorder logic (FO) with iteration, the fixpoint and while queries. The main result of the paper concerns the open problem of the relationship between fixpoint and while: they are the same iff ptime = pspace. These and other expressibility results are obtaine ..."
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Cited by 53 (13 self)
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We study two important extensions of firstorder logic (FO) with iteration, the fixpoint and while queries. The main result of the paper concerns the open problem of the relationship between fixpoint and while: they are the same iff ptime = pspace. These and other expressibility results are obtained using a powerful normal form for while which shows that each while computation over an unordered domain can be reduced to a while computation over an ordered domain via a fixpoint query. The fixpoint query computes an equivalence relation on tuples which is a congruence with respect to the rest of the computation. The same technique is used to show that equivalence of tuples and structures with respect to FO formulas with bounded number of variables is definable in fixpoint. Generalizing fixpoint and while, we consider more powerful languages which model arbitrary computation interacting with a database using a finite set of FO queries. Such computation is modeled by a relational machine...
A Query Language for NC
 In Proceedings of 13th ACM Symposium on Principles of Database Systems
, 1994
"... We show that a form of divide and conquer recursion on sets together with the relational algebra expresses exactly the queries over ordered relational databases which are NC computable. At a finer level, we relate k nested uses of recursion exactly to AC k , k 1. We also give corresponding resul ..."
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Cited by 16 (9 self)
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We show that a form of divide and conquer recursion on sets together with the relational algebra expresses exactly the queries over ordered relational databases which are NC computable. At a finer level, we relate k nested uses of recursion exactly to AC k , k 1. We also give corresponding results for complex objects. 1 Introduction NC is the complexity class of functions that are computable in polylogarithmic time with polynomially many processors on a parallel random access machine (PRAM). The query language for NC discussed here is centered around a form of divide and conquer recursion (dcr ) on finite sets which has obvious potential for parallel evaluation and can easily express, for example, transitive closure and parity. Divide and conquer with parameters e; f; u defines the unique function ', notation dcr (e; f; u), taking finite sets as arguments, such that: '(;) def = e '(fyg) def = f(y) '(s 1 [ s 2 ) def = u('(s 1 ); '(s 2 )) when s 1 " s 2 = ; For parity, we t...
Deterministic Semantics of SetOriented Update Sequences
 In Proceedings, Ninth International Conference on Data Engineering
, 1993
"... An iterator is proposed that allows to apply sequences of update operations in a setoriented way with deterministic semantics. Because the mechanism is independent of a particular model, it can be used in the relational and in objectoriented ones. Thus, the deterministic semantics of embedded SQL ..."
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Cited by 12 (4 self)
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An iterator is proposed that allows to apply sequences of update operations in a setoriented way with deterministic semantics. Because the mechanism is independent of a particular model, it can be used in the relational and in objectoriented ones. Thus, the deterministic semantics of embedded SQL cursors, and of triggers that are applied after (setoriented) SQL updates can be checked. Furthermore, the iterator can be used to apply objectoriented methods, which are usually update sequences defined on a single object, also to sets in a deterministic way. It turns out that the criteria that guarantee determinism are also used in semantic or multilevel concurrency control. 1 Introduction The paper deals with the general problem of defining update languages that are comparable in expressive power to typical query languages. When designing such an update language, one should pursue the following objectives: ffl genericity: update operations should be applicable to all types of objects...
RuleBased Languages
 ANNALS OF MATHEMATICS AND ARTIFICIAL INTELLIGENCE
, 1997
"... The paper presents a survey of the main formal rulebased languages and semantics. Both procedural (fixpoint) and declarative (modeltheoretic) semantics are defined and discussed, including inflationary and noninflationary fixpoint semantics, and the semipositive, stratified and wellfounded sem ..."
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Cited by 4 (0 self)
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The paper presents a survey of the main formal rulebased languages and semantics. Both procedural (fixpoint) and declarative (modeltheoretic) semantics are defined and discussed, including inflationary and noninflationary fixpoint semantics, and the semipositive, stratified and wellfounded semantics. The relative expressive power and complexity of the various languages are provided. Nondeterministic rulebased languages are also discussed, and it is shown how nondeterminism can circumvent some difficulties concerning the expressive power of the deterministic languages. Finally, languages with value invention (in the spirit of objectcreation in oodbs) are presented and issues of expressive power specific to such languages are discussed.
Computing on Structures
"... this paper various devices operating directly on structures, without encoding. The motivation and benefits for doing this are manyfold. On a fundamental level, encodings of structures seem to be a technical device rather than an intrinsic feature. This point has already been made by several mathemat ..."
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Cited by 3 (1 self)
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this paper various devices operating directly on structures, without encoding. The motivation and benefits for doing this are manyfold. On a fundamental level, encodings of structures seem to be a technical device rather than an intrinsic feature. This point has already been made by several mathematicians such as Tarski [Tar86], and Harvey Friedman [Fri71] (see Section 5). It has come up more recently in the context of databases, where devices computing on structures model more acurately database computation carried out against an abstract interface hiding the internal representation of data. Thus, the primary benefit of studying devices and languages computing on structures is that they clarify issues which are obscured in classical devices such as Turing machines. For example, they yield new notions of complexity, quite different from classical computational complexity. They reflect more acurately the actual complexity of computation, which, like database computation, cannot take advantage of encodings of structures. An example is provided by the query even on a set