D. Straube and T. Ozsu. Queries and query processing in object-oriented database systems. ACM Trans. on Information Systems, 8(4):387--430, 1990.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....to perform complementary semantic query optimizations in deductive objectoriented databases. 1 Introduction In object oriented database management systems, query optimization is performed by transforming algebraic expressions and by taking into account the physical representation of data [19][8] Semantic query optimization takes advantage of the semantic knowledge (e.g. integrity constraints) about the content of databases to reformulate a query into a less expensive yet equivalent query. A number of techniques have been followed to perform semantic query optimization in classical ....

D. D. Straube and M. T. Ozsu. Queries and query processing in object-oriented database systems. ACM Transactions on Information Systems, 8(4):387--430, October 1990.

.... without loss of generality, if s 1 ; s k are instances of ATOMIC, AGG or BIO, and s k 1 ; s n are instances of SET or SEQ, then p(s 0 1 ; s 0 n ; x) 9o k 1 2 s k 1 ; 9o n 2 s n : p(s 1 ; s k ; o k 1 ; o n ; x) The Select operator is similar to that of [SO90] which also allows multiple (set) operands. However, our Select operator is more powerful in that (1) it is polymorphic it takes any kind of operands (not only sets) and (2) if there are message sendings in the predicate p(s 1 ; s n ; x) then their invokers can be selected from the ....

Straube, D.D., and Ozsu, M.T. Queries and Query Processing in Object-Oriented Database Systems. Trans. on Info. Syst. 8 , 4, Oct. 1990.

....T 1 . Rule C1 to C7 can optimise queries by turning a predicate over objects into a predicate over the schema which needs to be evaluated only once at compile time instead of once for each object at runtime. Similar, but less general transformation rules for semantic optimisation are proposed in [35]. Quantifiers can be combined freely around a relational operator. The following transformation rules can be used to simplify some usage patterns. Many equivalences depend on the size of a collection, and hence the rules can only be applied immediately prior to execution when the sizes are ....

D. Straube and T. Ozsu. Queries and Query Processing in Object-Oriented Database Systems. ACM Transactions on Office Information Systems, 8(4):387--430, 1990.

....conditions, access nested structure, or produce nested results, an essential feature found in these languages is the nesting of queries, i.e. the embedding of a query into another query. The optimization of object oriented (oo) queries has been intensively studied using algebraic rewriting [4, 7, 23, 24, 25] or rewriting of path expressions [7, 13, 14] However, in spite of the importance of nested queries, we do not know of any research on their optimization. Nested queries in the oo context are usually translated into nested algebraic expressions which are evaluated through rather inefficient ....

D. Straube and T. Ozsu. Queries and query processing in object-oriented database systems. ACM Trans. on Information Systems, 8(4):387--430, 1990.

....search strategies have been developed in the relational context. Much effort has been done in order to adapt the techniques developed for the relational database systems to the object oriented environment. For instance, a number of researchers have worked on algebraic query rewriting (e.g. [17, 6, 18], others have extended relational search strategy [16] However, the characteristics of the object oriented environment had lead to consider entirely new techniques. First, objects are not flat tuples. An object may recursively refer to other objects. In this context, queries often involve ....

....rewriting techniques, ii) that allows easy and exhaustive factorization of duplicated subqueries, and (iii) that supports heuristics in order to reduce the optimization rewriting phase. There exist two main approaches to query rewriting in the object oriented context: the algebraic approach [17, 6, 18] and the one, that we call the type based approach, which transform pointer chasing into join operations [13, 15] We unify these two appoaches in one formalism. We show that it is just the lack of type information (membership to class extents) that makes it impossible to perform type based ....

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D. Straube and T. Ozsu. Queries and Query Processing in Object-Oriented Database Systems. Technical report, Department of computing science, university of Alberta, Edmonton, Alberta, Canada, 1990.

....equivalent to the one generated in Step 3 using a set of transformation rules, 5. given the algebra expressions generated in Step 4, identifying the most cost efficient one, based on a cost model, and 6. query evaluation. This approach to query processing is similar to the ones described in [7] and [8] The rules introduced in this article are transformation rules that are used in Step 4 of the above enumeration. Given a list of transformation rules, we use the Volcano Optimizer Generator [11] to generate a query optimizer. Rules may have a condition part that specifies under which ....

D.D. Straube and M.T. Ozsu. Queries and Query Processing in Object-Oriented Database Systems. ACM Transactions on Information Systems, 8(4):387--430, 1990.

....contained in a set. 10 x : e1 : bool; e2 : fg select[x:e1 ] e2 ) fg E[ select[x:e1 ] e2 ) fv 2 E[ e2 ] j E[ e 1fv=xg ] g: Projections restrict the interfaces of set elements as in the relational algebra (see also transformational filters in [1] In contrast to projections in [9, 23, 25] that generate objects or values, project is defined with object preserving semantics [21] Therefore, it can be used for hiding information, similar to assignments of instances to variables of a supertype: e : f[f 0 1 ; f 0 m ]g; f 0 1 ; f 0 m ] f1 ; fn ] project [f1 ....

D.D. Straube and M.T. Ozsu. Queries and query processing in objectoriented databases. ACM Transactions on Office Information Systems, 8(4):387--430, October 1990.

....in more comprehensible queries. Optimisation opportunities have been identified for some of the new features. Some optimisations allow syntax level transformation at compile time while others suggest simplification at run time. These optimisations not only subsume previous work of the same kind [Str90] but also include many new optimisations. The organisation of this chapter is as follows. Section 4.1 describes the development of object comprehensions. Section 4.2 presents the syntax of object comprehensions. Section 4.3 demonstrates object comprehensions using a set of example queries. ....

....c2 OEOE c1 4.2 x hasClass c2 : 9 c : ClassName ffl c OEOE c1 c OEOE c2 5 (x hasClass c1) or (x hasClass c2) x hasClass c1 c2 OEOE c1 Table 4.2: Optimising Class Testing. All these transformations can be applied at compile time. This set of semantic optimisation rules subsumes those found in [Str90] An interpretation of the rules is given below Object Comprehensions 58 and followed by an example of the usage of one of the rules. Rule 1 Every class is related directly or indirectly to the root class by the ISA relationship. Entity is the root class. Therefore every object is also of class ....

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D.D. Straube. Queries and Query Processing in Object-Oriented Database Systems. PhD thesis, University of Alberta, Canada, 1990.

....are not studied in this thesis. The study of optimisation generates a set of logical and semantic transformation rules. Search strategies used for transformation are not covered but preliminary results for non recursive queries can be found in [Mit93] Execution plan generation is studied in [SO90] but the choice between generation plans is only very briefly discussed. The research reported in this thesis is carried out in the context of a formal data model and has not been integrated 1.2. Contributions 3 into a running system. However given a suitable implementation platform, it is ....

....in this chapter includes the significant features found in most object oriented data models, for example, IRIS [LK86] GemStone [Ser87] ORION [Kim90] ONTOS [Ont91a] and O 2 [BDK92] to name but a few. A number of object oriented data models have been given a formal specification [MH87, Wol87, SO90, DD91, BDK92, Nor92] however, the various features of objectorientation are studied separately. The reference data model provides a uniform framework for the study of their interaction. In particular, it supports a generalised form of method overloading and addresses the problem of statically ....

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D. Straube and T. Ozsu. Queries and Query Processing in Object-Oriented Database Systems. ACM Transactions on Office Information Systems, 8(4):387--430, 1990.

....binary joins in another order. One could possibly use list notation for arguments join(R, multijoin(L) multijoin(cons(R, L) but that still leaves the problem of providing transforms to change list orderings. Some work on transforms in object algebras with variadic operators already exists [14]. 4.1.5 Non Local Transforms Some transforms seem to have a non local character that is not easily expressed with term rewriting [15] Here, relief might come from transformation grammar techniques used in natural language processing for specifying non local transforms on sentential forms [16] ....

Straube, DD and zsu, MT. Queries and query processing in object-oriented database systems. ACM Trans. on Information Systems 8(4):387-430, October 1990.

....alternatives to object navigation. Kemper and Moerkotte explore the use of relations to support navigation [KM90] A variety of proposals have been made for optimization based on algebraic transformation rules for query operations[LB89, Osb88, Zdo89, SO89, BK90b] For example, Straube and Ozsu [Str90] propose a methodology for query optimization that includes calculus based optimization, the transformation of calculus based queries to algebraic form, type checking of algebraic expressions, the application of algebraic transformation axioms, and the generation of access plans for the algebraic ....

Dave D. Straube. Queries and Query Processing in Object-Oriented Database Systems. PhD thesis, Univ. of Alberta, December 1990.

.... unary and binary to represent entity categories and relationships, respectively, means that our algebra differs from other algebras in its provision of operations specific to binary collections (relationships) Andersen [And91] Scholl et al. [SST92] Shaw and Zdonik [SZ89] SZ90] and Straube [Str90] all restrict their attention to set collections. Both Cluet et al. [CDLR90] and Vandenberg and DeWitt [VD91] cater for multiple kinds of collections. Arising from the two forms of collections unary and binary the collection algebra has two groups of operations. Any operation that can be ....

D. D. Straube. Queries and Query Processing in Object-Oriented Database Systems. PhD thesis, University of Alberta, Edmonton, Alberta, Canada, December 1990.

....a type t i is a subtype of type t j or that t j is a supertype of type t i . Over this subtype supertype relation there is inheritance. A subtype inherits all of its supertype s properties. The subtype supertype relation can also be seen as a specialization generalization relation [10]. Since a subtype can only add or specialize existing properties of its supertype it can be seen as a specialization. As an example consider the following type tree Figure 1 Type tree The type Person has two interface functions 2 , Name and Ssno. The type Employee is a subtype of type Person ....

Straube, D.D. and zsu, M.T., "Queries and Query Processing in Object-Oriented Database Systems", ACM Trans. on Information Systems, Vol. 8, No. 4, October 1990

.... was supported by NUTEK (The Swedish National Board for Industrial and Technical Development) TFR (Swedish Research Council for Engineering Science) and CENIIT (The Center for Industrial Information Technology) 1996 96 28 1 1 Introduction Research on object oriented database systems [4] [28] is often motivated by claiming that it is targeting applications such as office automation systems, computer aided design or finite element analysis (FEA) 5] 6] 18] The object oriented model is a powerful model which contains features that support the programmer in managing the complexity of ....

....are not part of the model. In this paper we show the benefits of having these features when modelling complex applications. In [19] a low level algebra for matrix operations is proposed. Object oriented databases have been subject of extensive research during the last decade, e.g. 4] 5] 6] [28]. However, to the best of our knowledge processing queries with multi methods in object oriented database systems has not yet been addressed. With multi methods additional complexity is introduced into the system since type resolution becomes more complex than type resolution of pure ....

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D. D. Straube, M. T. zsu, "Queries and Query Processing in Object-Oriented Database Systems", ACM Transactions on Information Systems, Vol. 8, No. 4, October 1990.

....and cost model for DTR and its inverse is defined in section 5.0. In section 6.0 the performance measurement is presented, and finally section 7.0 summarizes our experiences and outlines future work. 2. 0 Related work Object Oriented query processing has gained much attention recently [5] 17] [20] [21] 23] However, to the best of our knowledge, the problem of using inverted late bound functions has not been dealt with. The problem of having late bound function calls in execution plans was identified in the Revelation project [5] as a problem that still presents a challenge . A problem ....

....This is a very important characteristic that is fundamental to the AMOS data model. To give a more precise description we need the notion of the extent of a type. The set of all instances of a type t that is not also a member of any subtype of type t is called the extent of type t denoted ext(t) [20] [6] The deep extent [20] of a type t, denoted ext (t) is the union of the extents of each type in the subtree of the type hierarchy rooted at type t. If a type t i is a subtype of type t j then the deep extent of type t j will contain the deep extent of type t i , i.e. t i t j ext ....

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D. D. Straube, M. T. zsu, "Queries and Query Processing in Object-Oriented Database Systems", ACM Trans. on Information Systems, Vol. 8, No. 4, October 1990

.... Some of the models and query languages are either direct followups of the work on nested relations complex objects or at least have been developed in the same research group (such as [16, 41, 112, 111, 49, 33] Others, even though developed independently, show the same similarities (for example [80, 12, 130, 116, 8, 124, 73]) This is a clear indication that the results on complexity, expressive power, optimization, and implementation issues obtained in the context of nested relations complex objects can be utilized in the new field of objectoriented databases. For example, most of the equivalences stated for object ....

D.D. Straube and M.T. Ozsu. Queries and query processing in object-oriented databases. Technical Report TR 90--11, Dept. of Computing Science, University of Alberta, Edmonton, Alberta, Canada, April 1990. To appear in ACM TOIS.

.... Keywords: Object oriented database systems, semantic and rule based query optimization 1 Introduction Progress in the optimization of declarative object oriented queries has been concentrated on structural aspects, like the manipulation of complex data values and the usage of path indices [6] 7][25]. In algebraic query optimization the optimization process is based on equivalences for the built in query algebra operators. In semantic query optimization it is recognized that also application specific knowledge in form of constraints on attributes can be used. But in most approaches the ....

....is through path methods: E 1 : p In Paragraph: p document( b p.section.document is mapped to map a 2 , a 1 document( A 1 a 1 , Paragraph ) # map a 2 , a 1 .section.document ( A 1 a 1 , Paragraph ) 8. In older object oriented algebras this was not always the case, see e.g. [25]. On the other hand, our map operator is comparable to the operator denoted by # a:e in [10] 13 2. Equivalent Conditions This type is very similar to the previous one, except that here we consider only the equivalence of boolean expressions: x IN C: cond 1 (x) # cond 2 (x) We can ....

[Article contains additional citation context not shown here]

D.D. Straube, M.T. Özsu: "Queries and Query Processing in Object-Oriented Database Systems", ACM Transactions on Information Systems, vol. 8, no. 4, pp. 387--430, October 1990.

....equivalent to the formal languages, which makes it easier to perform logical transformations and argue about its safety. Query optimization is essential for efficient execution plans. A lot of research in extending relational query optimization techniques has been done in recent years (e.g. [31]) A more viable approach is to use object oriented design to develop an extensible query optimizer that can evolve and improve its performance over time. An extensible query optimizer is under development for TQL, where the components of the optimizer such as cost functions, algebraic ....

D.D. Straube and M.T. Ozsu. Queries and Query Processing in Object-Oriented Database Systems. ACM Transactions on Information Systems, 8(4):387--430, October 1990.

No context found.

D. Straube and T. Ozsu. Queries and query processing in object-oriented database systems. ACM Trans. on Information Systems, 8(4):387--430, 1990.

No context found.

D.D. Straube and M.T.  Ozsu, \Queries and Query Processing in Object-Oriented Database Systems," ACM Transactions on Information Systems, Vol. 8, No. 4, pp. 387-430, 1990.

No context found.

Dave D. Straube. Queries and Query Processing in Object-Oriented Database Systems. PhD thesis, Department of Computing Science, University of Alberta, Edmonton, Alberta, Canada, December 1990. Technical Reporrt TR90-33.

No context found.

D. Straube and T. Ozsu. Queries and query processing in object-oriented database systems. ACM Trans. on Information Systems, 8(4):387--430, 1990.

No context found.

Straube, D. and zsu, M. Queries and query processing in objectoriented database systems. ACM Ttrans. Information Systems 8, 4 (1990), 387-430.

No context found.

D.D. Straube and M.T. Ozsu. Queries and query processing in object-oriented databases. Technical Report TR 90--11, Dept. of Computing Science, University of Alberta, Edmonton, Alberta, Canada, April 1990. To appear in ACM TOIS.

No context found.

D.D. Straube and M.T. Ozsu. Queries and query processing in object-oriented databases. Technical Report TR 90--11, Dept. of Computing Science, University of Alberta, Edmonton, Alberta, Canada, April 1990. To appear in ACM TOIS.

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