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13
Naturally Embedded Query Languages
 LNCS 646: Proceedings of 4th International Conference on Database Theory
, 1992
"... We investigate the properties of a simple programming language whose main computational engine is structural recursion on sets. We describe a progression of sublanguages in this paradigm that (1) have increasing expressive power, and (2) illustrate robust conceptual restrictions thus exhibiting inte ..."
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Cited by 132 (26 self)
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We investigate the properties of a simple programming language whose main computational engine is structural recursion on sets. We describe a progression of sublanguages in this paradigm that (1) have increasing expressive power, and (2) illustrate robust conceptual restrictions thus exhibiting interesting additional properties. These properties suggest that we consider our sublanguages as candidates for "query languages". Viewing query languages as restrictions of our more general programming language has several advantages. First, there is no "impedance mismatch" problem; the query languages are already there, so they share common semantic foundation with the general language. Second, we suggest a uniform characterization of nested relational and complexobject algebras in terms of some surprisingly simple operators; and we can make comparisons of expressiveness in a general framework. Third, we exhibit differences in expressive power that are not always based on complexity arguments...
On The Power Of Languages For The Manipulation Of Complex Objects
 In Proceedings of International Workshop on Theory and Applications of Nested Relations and Complex Objects
, 1993
"... Various models and languages for describing and manipulating hierarchically structured data have been proposed. Algebraic, calculusbased and logicprogramming oriented languages have all been considered. This paper presents a general model for complex objects, and languages for it based on the thre ..."
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Cited by 121 (6 self)
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Various models and languages for describing and manipulating hierarchically structured data have been proposed. Algebraic, calculusbased and logicprogramming oriented languages have all been considered. This paper presents a general model for complex objects, and languages for it based on the three paradigms. The algebraic language generalizes those presented in the literature; it is shown to be related to the functional style of programming advocated by Backus. The notion of domain independence familiar from relational databases is defined, and syntactic restrictions (referred to as safety conditions) on calculus queries are formulated, that guarantee domain independence. The main results are: The domainindependent calculus, the safe calculus, the algebra, and the logicprogramming oriented language have equivalent expressive power. In particular, recursive queries, such as the transitive closure, can be expressed in each of the languages. For this result, the algebra needs the pow...
Normal Forms and Conservative Properties for Query Languages over Collection Types
 In Proceedings of 12th ACM Symposium on Principles of Database Systems
, 1993
"... Strong normalization results are obtained for a general language for collection types. An induced normal form for sets and bags is then used to show that the class of functions whose input has height (that is, the maximal depth of nestings of sets/bags/lists in the complex object) at most i and out ..."
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Cited by 54 (25 self)
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Strong normalization results are obtained for a general language for collection types. An induced normal form for sets and bags is then used to show that the class of functions whose input has height (that is, the maximal depth of nestings of sets/bags/lists in the complex object) at most i and output has height at most o definable in a nested relational query language without powerset operator is independent of the height of intermediate expressions used. Our proof holds regardless of whether the language is used for querying sets, bags, or lists, even in the presence of variant types. Moreover, the normal forms are useful in a general approach to query optimization. Paredaens and Van Gucht proved a similar result for the special case when i = o = 1. Their result is complemented by Hull and Su who demonstrated the failure of independence when powerset operator is present and i = o = 1. The theorem of Hull and Su was generalized to all i and o by Grumbach and Vianu. Our result genera...
Normal Forms And Conservative Extension Properties For Query Languages Over Collection Types
 Journal of Computer and System Sciences
, 1995
"... Strong normalization results are obtained for a general language for collection types. An induced normal form for sets and bags is then used to show that the class of functions whose input has height (that is, the maximal depth of nestings of sets/bags/lists in the complex object) at most i and outp ..."
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Cited by 27 (8 self)
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Strong normalization results are obtained for a general language for collection types. An induced normal form for sets and bags is then used to show that the class of functions whose input has height (that is, the maximal depth of nestings of sets/bags/lists in the complex object) at most i and output has height at most o definable in a nested relational query language without powerset operator is independent of the height of intermediate expressions used. Our proof holds regardless of whether the language is used for querying sets, bags, or lists, even in the presence of variant types. Moreover, the normal forms are useful in a general approach to query optimization. Paredaens and Van Gucht proved a similar result for the special case when i = o = 1. Their result is complemented by Hull and Su who demonstrated the failure of independence when powerset operator is present and i = o = 1. The theorem of Hull and Su was generalized to all i and o by Grumbach and Vianu. Our result generali...
Functional Database Query Languages as Typed Lambda Calculi of Fixed Order (Extended Abstract)
 In Proceedings 13th PODS
, 1994
"... We present a functional framework for database query languages, which is analogous to the conventional logical framework of firstorder and fixpoint formulas over finite structures. We use atomic constants of order 0, equality among these constants, variables, application, lambda abstraction, and le ..."
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Cited by 12 (5 self)
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We present a functional framework for database query languages, which is analogous to the conventional logical framework of firstorder and fixpoint formulas over finite structures. We use atomic constants of order 0, equality among these constants, variables, application, lambda abstraction, and let abstraction; all typed using fixed order ( 5) functionalities. In this framework, proposed in [21] for arbitrary order functionalities, queries and databases are both typed lambda terms, evaluation is by reduction, and the main programming technique is list iteration. We define two families of languages: TLI = i or simplytyped list iteration of order i +3 with equality, and MLI = i or MLtyped list iteration of order i+3 with equality; we use i+3 since our list representation of databases requires at least order 3. We show that: FOqueries ` TLI = 0 ` MLI = 0 ` LOGSPACEqueries ` TLI = 1 = MLI = 1 = PTIMEqueries ` TLI = 2 , where equality is no longer a primitive in TLI = 2 . We also show that ML type inference, restricted to fixed order, is polynomial in the size of the program typed. Since programming by using low order functionalities and type inference is common in functional languages, our results indicate that such programs suffice for expressing efficient computations and that their MLtypes can be efficiently inferred.
Persistent Caching: An Implementation Technique for Complex Objects with Object Identity
 IEEE Transactions on Software Engineering
, 1992
"... Database systems that can efficiently manage complex objects are increasingly needed in many different fields such as office automation, knowledge processing, CAD/CAM, CASE, etc. A lot of recent complex object database systems support the concepts of object identity and object identifier. Followi ..."
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Cited by 12 (4 self)
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Database systems that can efficiently manage complex objects are increasingly needed in many different fields such as office automation, knowledge processing, CAD/CAM, CASE, etc. A lot of recent complex object database systems support the concepts of object identity and object identifier. Following an object identifier to access the referenced object is called navigation operation and is an essential operation in dealing with complex objects. Navigation operation is a difficult operation to implement efficiently since every navigation operation inherently causes one disk access operation. This paper proposes a scheme to notably accelerate the navigation operation among a sea of complex objects, by increasing the effectivenumber of objects in one disk page. The main concept of the presented technique is threefold: The first is to store a cached value within a complex object that is referencing another complex object. The second is that when the referenced object is to be updated the update propagation is delayed until the time when the cached value is referenced. Lastly, the third idea is to utilize a hashed table on main memory to efficiently validate the consistency between the cached values and the original values. Index terms  Complex objects, objectoriented database, object identity, persistent objects, caching, and delayed update propagation. I
A SQLlike Query Calculus for ObjectOriented Database Systems
 Proc. Int. Symp. on ObjectOriented Methodologies and Systems (ISOOMS'94
, 1994
"... . Currently much effort is being spent on providing objectoriented databases with ad hoc query facilities. In this paper we present a SQLlike query calculus whose major contribution lies in its inherent orthogonality and rigorous mathematical foundation. The calculus is essentially a calculus of co ..."
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Cited by 8 (7 self)
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. Currently much effort is being spent on providing objectoriented databases with ad hoc query facilities. In this paper we present a SQLlike query calculus whose major contribution lies in its inherent orthogonality and rigorous mathematical foundation. The calculus is essentially a calculus of complex values but it is defined independently of any concrete database model. The calculus can be used to formulate queries in valuebased and objectbased data models. Moreover it provides a general facility for the manipulation of complex values. 1 Introduction Objectoriented database systems (OODB) are usually embedded in a programming language environment providing full computational power. Consequently, designers of OODB at first did not feel the need to integrate ad hoc query facilities into their systems. However, it has been recognized that some associative retrieval is of importance even for OODB [8, 12, 13]. A welltried ad hoc query language is SQL. SQL came up with relational da...
Transforming Conceptual Data Models into an Object Model
 In ERâ€™92
, 1992
"... . In this paper a conceptually simple structural object model focusing on object types, attributes and ISA relationships is introduced. The model is derived mainly from an extended EntityRelationship approach, but concepts from other semantic and objectoriented models have influenced its features. ..."
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Cited by 7 (0 self)
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. In this paper a conceptually simple structural object model focusing on object types, attributes and ISA relationships is introduced. The model is derived mainly from an extended EntityRelationship approach, but concepts from other semantic and objectoriented models have influenced its features. It is shown how highlevel conceptual data models can be mapped to this model, and to what extent the object model subsumes classical modeling paradigms. 1 Introduction In recent years numerous data models for the conceptual modeling of information systems have been proposed. Among them there are semantic data models like SDM [13], IFO [3] and (extended) ER models [8, 9, 10, 24, 31, 34], complex object models like [1, 18, 26], purely objectbased models like FDM [28] as well as objectbased models with complex values such as [22]. All the approaches have different motivation, terminology, and aims. Here we aim to show you how some of these models can be translated into a conceptually simpl...
The Restricted and Bounded Fixpoint Closures of the Nested Algebra are Equivalent
 In Proceedings of DBPL'95
, 1995
"... The nested model is an extension of the traditional, "flat" relational model in which relations can also have relationvalued entries. Its "default" query language, the nested algebra, is rather weak, unfortunately, since it is only a conservative extension of the traditional, "flat" relational algeb ..."
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Cited by 4 (1 self)
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The nested model is an extension of the traditional, "flat" relational model in which relations can also have relationvalued entries. Its "default" query language, the nested algebra, is rather weak, unfortunately, since it is only a conservative extension of the traditional, "flat" relational algebra, and thus can only express a small fraction of the polynomialtime queries. Therefore, it was proposed to extend the nested algebra with a leastfixpoint construct, but the resulting language turned out to be too powerful: many inherently exponential queries could also be expressed. Two polynomialtime restrictions of the leastfixpoint closure of the nested algebra were proposed: the restricted leastfixpoint closure (by Gyssens and Van Gucht) and the bounded fixpoint closure (by Suciu). Here, we prove that both restrictions are equivalent in expressive power. We also exhibit a proof technique, called type substitution, by which we reduce our result to its obvious counterpart in the "fla...