We propose a database logic which accounts in a clean declarative fashion for most of the “object-oriented” features such as object identity, complex objects, inheritance, methods, etc. Furthermore, database schema is part of the object language, which allows the user to browse schema and data using the same declarative formalism. The proposed logic has a formal semantics and a sound and complete resolution-based proof procedure, which makes it also computationally attractive.

Pointer swizzling is the conversion of database objects between an external form (object identifiers) and an internal form (direct memory pointers). Swizzling is used in some object-oriented databases, persistent object stores, and persistent and database programming language implementations to speed manipulation of memory resident data. Here we describe a simplifying model of application behavior, revealing those aspects where swizzling is most relevant in both benefits and costs. The model has a number of parameters, whichwehavemeasured for a particular instance of the Mneme persistent object store, varying the swizzling technique used. The results confirm most of the intuitive, qualitative tradeoffs, with the quantitative data showing that some performance differences between schemes are smaller than might be expected. However, there are some interesting effects that run counter to naive intuition, most of which we explain using deeper analysis of the algorithms and data struc...

We define an algebra which synthesizes relational query concepts with object-oriented databases. The algebra fully supports abstract data types and object identity while providing associative access to objects, including a unique join capability. The operations take an abstract view of objects and access typed collections of objects through the public interface defined for the type. The algebra supports access to relationships implied by the structure of the objects, as well as the definition and creation of new relationships between objects. The structure of the algebra and the abstract access to objects offer opportunities for query optimization. 1 Introduction Object-oriented databases are emerging in response to a requirement for more complete modelling of complex data in modern design and office environments. Such databases attempt to combine the modelling power of object-based programming models with traditional database concepts such as persistence, data sharing, cons...

A language for databases with sets, tuples, lists, object identity and structural inheritance is proposed. The core language is logic-based with a fixpoint semantics. Methods with overloading and methods evaluated externally providing extensibility of the language are considered. Other important issues such as updates and the introduction of explicit control are discussed. 1 INTRODUCTION The success of the relational database model [19, 38, 27] is certainly due to technological advances such as fast query processing or reliable concurrency control. However, we believe that a major factor in that success has been the existence of simple-to-use languages allowing the definition and manipulation of data. This has to be remembered while considering future generations of database systems. Object-oriented database systems are now being developed, e.g., [15, 12, 22, 39, 36]. An object-oriented approach [24] is used to answer the needs of a much wider variety of applications. Most of th...

We study here how to provide the designer of geographic databases with a database query language extensible and customizable. The model presented here is a first step toward a high level spatial query language adapted to the manipulation of thematic maps. For this, we take as an example a toy application on thematic maps, and show by using a complex objects algebra that application dependent geometric operations can be expressed through an extension of the replace operator of [AB88].

This paper argues that comprehensions, a construct found in some programming languages, are a good query notation for DBPLs. It is shown that, like many other query notations, comprehensions can be smoothly integrated into DBPLs and allow queries to be expressed clearly, concisely and efficiently. More significantly, two advantages of comprehensions are demonstrated. The first advantage is that, unlike conventional notations, comprehension queries combine computational power with ease of optimisation. That is, not only can comprehension queries express both recursion and computation, but equivalent comprehension transformations exist for all of the major conventional optimisations. The second advantage is that comprehensions provide a uniform notation for expressing and performing some optimisation on queries over several bulk data types. The bulk types that comprehensions can be defined over include sets, relations, bags and lists. A DBPL can also be automatically extended to provide and partially optimise comprehension queries over new bulk types constructed by the application programmer, providing that the new type has some well-defined properties. 1

In a class hierarchy, a “role set ” is t,he set of classes where an object may reside simultaneously. A “migration pattern ” is a sequence of role sets. A “migration inventory, ” which is a set, of migrat,ion patterns, is viewed as a dynamic const,raintm on ohjrct migration. A set of transact ious is “sound ” wrt a11 inventory if it. generates only pat.t.t~rns in the invrntory; “complete ” if all pat,terns in the invent,ory can be generated. An initial stucly on characterizing migration inventories of transact,ions is presented. Three update languages are considered: SL which contains five operat,ors, CSL+ which ext rn(ls SL wit.h posit.ivc conditionals, and CSL which allows hot,h positive and negative condit.ionals. Four kinds of invent.orics are studied based on ln~znrss and znj~~,rtl~ntr s/art. It is shown that inventories produced by SL t,ransactions are regular and every regular inventory can be generated by SL transactions. Soundness and complet,eness for SL t,ransactions are decidahlt3. lnvc\llt,orics gpnrrated by CSL (CSL+) t,ra.nsactions arc r.e‘. and every r.e. inventory can be generat,rd by (:SL+ (CSL) transa.ctions under nonimmediate st,art,. It is also show t,hat, every r.e. immediate-start invent,ory can be obtained by a left quotient, of t,he invent,ory of CSL+ (CSL) transactions hy a regular seb. The exact, charact#erizat.ions are open. However, cvrry contrxl-frcr srt can be generat,ed. Soundness and rmllplPt~enms for ($1, (CSL+) t,ransa.ctions are undecidahlr. 1

T ROLL is a language to specify information systems with dynamic behavior. Here, we elaborate on the specification of object aggregation in T ROLL . We distinguish between two kinds of aggregation, static and dynamic aggregation. Static aggregation means that the composition of objects is described using predicates over constant properties. Dynamic aggregation means that we may alter the composition of objects by invoking special operations (events) that are implicitly defined for each dynamic complex object. Additionally, we describe the specification of disjoint complex as a means for structuring a specification. We introduce language features to describe object aggregation and give some hints towards their semantics. 1 Introduction The first steps in an object-oriented approach to information system development concentrate on the abstract description of the relevant static and dynamic aspects of real-world objects (the Universe of Discourse, UoD) [Gri82, RBP + 90, Boo90] (concept...

In this thesis we address the problem of providing efficient processing of queries in the extensible environment induced by object-oriented databases. We define a framework for query processing in an object-oriented database and develop designs for major components of this framework. The framework encompasses an object-oriented data model, an algebra to query over that model, transformation rules for the algebra, an internal representation for queries expressed in the algebra, a cost model for analyzing query expressions, and an architecture for an extensible query optimizer. The major contributions of this thesis are an algebra and transformation rules, a representation, and an architecture for extensible query optimization. We show how these components fit into the framework and interact with each other. The EQUAL query algebra presented in this thesis is the first query algebra for object-oriented database systems to be completely consistent with data abstraction, and one of the few...

Query optimizers for persistent object systems should be extensible to react to user-supplied abstract types. Current architectures support only a single, non-extensible technique for controlling the optimization process. We propose an alternative to the current extensible architectures that will support multiple optimizer control strategies and the addition of new control strategies. The optimizer consists of a collection of optimization regions, each of which can transform queries according to a particular control strategy, set of transformations and cost model. A global optimizer control coordinates the movement of a query between these regions. This architecture provides extensibility in the optimizer's repertoire of control strategies through the addition of new regions. In this paper we describe our approach and demonstrate its utility by following the optimizer as it works on an example query. The optimizer will move the query between three distinct regions. The different region...