B. Vance. Towards an Object-Oriented Query Algebra. Technical Report CS/E 91-008, Oregon Graduate Institute, U.S.A., January 1992.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....algebras for data models is to use them as vehicles for query optimisation in systems supporting high level interfaces such as query languages. A large number of algebras have been proposed for data models richer than the relational model [Osb88, Day89, CDLR89, SZ89, SO90, VD90, DD91, WT91, Van92, Alh92, Nor92, AB93, Mit93, GM93, LW93] Many of these algebras extend the relational algebra to manipulate richer modelling constructs and object identifiers as well as to provide more expressive and computational powers. Others take a fundamentally different approach and draw on the experience ....

....structure hence incurs a lower cost than evaluating the operations individually. It can also be argued that the emphasis on control structures would benefit more in the object oriented paradigm where navigation seems to dominate. Different variations of reduce have been studied, for example, in [Van92] It is a very powerful operation with which many useful operations can be expressed. For instance, powerset can be expressed in terms of reduce. power( E ) reduce( single ( empty ( nil ) x :union( single ( empty ( nil ) single ( single ( x ) x y:map( m:map( n:single ( ....

B. Vance. Towards an Object-Oriented Query Algebra. Technical Report CS/E 91-008, Oregon Graduate Institute, U.S.A., January 1992.

....be composed freely. We also expect it to incorporate object identity and the ability to operate on user defined types through messages. There have been numerous proposals for object algebras, such as those of Beeri and Kornatsky [8] and Osborn [9] We expect that ours will resemble those of Vance [10] and Vandenberg [11] It might seem, then, that specifying the parser optimizer interface is a matter of selecting a semantic formalism, such as set theory, equational specifications or denotational semantics, and giving a definition to each operator in the algebra. However, from the point of ....

Vance, B. Toward an object-oriented query algebra. Computer Science & Engineering report 91-08, Oregon Graduate Inst., May 1991.

....object algebra, query languages, complex objects, conceptual schema. 1 Introduction The characteristics of a database algebra have to reflect the properties of the algebraic structures for which algebraic operations are intended. From this perspective, the differences between an object algebra [55, 2, 47, 53, 32, 29, 33, 51] and an algebraic language defined for the manipulation of relations [16, 41, 1] for instance, can be regarded as the consequences of differences in the underlying data models. The features that have to be included in the object algebra are operations for handling the modelling constructs which ....

.... manipulation of complex objects used in this approach are most often variants of the operations apply to all and the operation (tuple) construction [7] The database algebras that have been influenced by the functional languages include: Complex Object Algebra [2] Object Oriented Query Algebra [53] and Query Algebra [47] The above two types of operations together are commonly referred to as restructuring operations [2] A given object algebra either uses one of the approaches, or combines both of them. In general, the restructuring operations are appropriate for expressing queries that: ....

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B. Vance, Towards an object-oriented query algebra, Tech. Report CS/E91-008, Dept. Comp. Science and Eng., Oregon Graduate Institute, Jan. 1991.

....supports many of the features commonly present in object oriented systems and supports some additional features. More recently, a system called AQUA (A QUery Algebra) is the result of a joint effort among researchers who have participated in the design of previous object oriented algebras [Shaw90, Vanc92, Vand91]. AQUA has been designed to address a number of detailed modeling issues that we believe needed further work, but the primary goal of this work has been the design of an algebra that would serve as the input to a broad class of query optimizers. AQUA and the data model on which it is based are ....

....to be nested. In the complex object models, there is no restriction on the ordering or number of applications of these constructors. There is no standard algebra for such objects, but several algebras have been proposed. Finally, algebras have been defined for some object oriented data models [Yu91, Shaw90, Vand91, Vanc92]. These models can be viewed as extending the complex object models with the notions of object identity, 7 inheritance, and methods (procedures defined to operate on objects of a certain type) There is no accepted standard here either. Most recently, AQUA extends the structures to accommodate ....

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B. Vance, "Towards an object-oriented query algebra", Tech. Report CS/E91-008, Dept. of Computer Science and Eng., Oregon Graduate Institute, Beaverton, OR, January 1992.

....this is actually not as restrictive as it may seem. In [13] we have shown that the combinators needed for the compilation of a full AEedged declarative object query language like OQL can entirely be expressed by foldr. Other proposals for expressive query languages also relied on variants of foldr [1, 21, 5]. Cheap (or foldr build) deforestation is a one step transformation that does not involve a fold step. It relies on the observation that a list built from the constructors : cons) and [ nil) which is subsequently reduced by a foldr may actually be reduced during its construction. Furthermore, ....

B. Vance. Towards an Object-Oriented Query Algebra. Technical Report 91008, Oregon Graduate Institute of Science & Technology, January 1992.

....reducing the need for extra summation loops. This applies to aggregations in general, covering OQL s count, max min, avg, exists, and forall (where the latter two aggregate boolean values) The incorporation of general aggregations has been realized by means of fold operators of various sorts [1,2,17,7,13]. fold[ Phi; f ] E) applies function f to every element of E and accumulates the function results via the binary operator Phi. sum(E) is thus implemented by fold[ id] E) The uses of fold are manifold. We will use folding of boolean values to implement quantification as well. Consider fold[ ....

Bennet Vance. Towards an Object-Oriented Query Algebra. Technical Report 91--008, Oregon Graduate Institute of Science & Technology, January 1992.

....space of alternate plans is not very rich because the components of a processing template do not expose which algorithms are used to access data. There is a single implementation for each operator, and all variations in plans essentially come via permutations of arguments. As part of the Revelation[45, 25, 87], Bennet Vance has developed Rexall[88] a functional plan language with support for objects. Rexall allows the recognition of situations where the same physical operator is used to compute different logical operators. The two instances of the physical operator can be combined, eliminating the ....

Bennet Vance. Towards an object-oriented query algebra. Technical Report CS/E-91-008, Oregon Graduate Institute of Science and Technology, January 1992.

....proposals as well as those of other researchers on the topic have explored some of the fundamental issues and provided the starting point for the work reported here. AQUA (A QUery Algebra) is the result of a joint effort among researchers who have participated in the design of previous algebras [26, 30, 31]. AQUA has been designed to address a number of detailed modeling issues that we believe needed further work, but the overarching goal for this work has been the design of an algebra that would serve as the input to a broad class of query optimizers. In this way, it could be used as a de facto ....

....similar goals, but not necessarily in all these areas at once, and our mechanisms for achieving these goals differ substantially from those of our predecessors. Many of the specific constructs of AQUA were inspired by or drawn from the EXTRA EXCESS system [31] ENCORE EQUAL [26] and Revelation [30]. AQUA is intended to support large numbers of bulk types and to do so in a flexible, uniform way, such that the addition of other bulk types later on will be straightforward. 6] proposes a meta level algebra for collections of complex objects with identity and also includes some transformation ....

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B. Vance. Towards an object-oriented query algebra. Tech. Report CS/E91-008, Dept. of Computer Science and Eng., Oregon Graduate Institute, Beaverton, OR, January 1992.

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Bennet Vance. Towards an Object-Oriented Query Algebra. Technical Report 91--008, Oregon Graduate Institute of Sciene & Technology, January 1992.

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Bennet Vance. Towards an Object-Oriented Query Algebra. Technical Report 91--008, Oregon Graduate Institute of Sciene & Technology, January 1992.

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