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An important problem of OODB query optimization is to perform efficiently path traversals expressed in queries involving complex objects. Most optimizers consider a restricted search space with only traversals starting at either end of the path. In this paper, we propose a general framework for optimizing OODB queries including overlapping path traversals and explicit joins. This makes it possible to explore any traversal of a path supported by the target execution system. Furthermore, our approach enables the application of deterministic search strategies...
In this paper we present the design of an optimiser for the object-oriented database P/FDM. We explore the approach of using a navigational query language, based on Shipman's original Daplex language [Sh 81] for the optimisation. The advantage of this is that it fits the navigational style of querying very well, but it is also optimisable. The optimisation is based on the equivalence of most Daplex...
We address the generation of execution plans for object-oriented database queries. This is a challenging area of study because, unlike the relational algebra, a uniformly accepted set of object algebra operators has not been defined. Additionally, a standardized object manager interface analogous to storage manager interfaces of relational systems does not exist. We define the interface to an object...
Recently, a new access method, the Hierarchical-Tree (H-tree) was proposed as an efficient access method for object-oriented database that supports superclass-subclass relationship. We show that, the H-tree indexing scheme is indeed a general access method for the new generation DBMS that most probably will support the object-oriented concept and have the deductive capability. The simplest form of...
Recently the author introduced the so called stationary semantics which extends the well-founded semantics of normal logic programs to the class of all disjunctive logic programs and deductive databases. The stationary semantics also extends the perfect model semantics defined earlier for stratified disjunctive databases. As a result, the stationary semantics is the only currently known semantics...
In this paper we introduce G-Log, a declarative graphical query language which combines of the expressive power of logic, the modelling power of objectorientedness and the representation power of graphs. As in the case of prolog, G-Log may be used in a totally declarative way, as well as in a “more procedural” way. Furthermore, it provides an intuitive and flexible graphical tool for non-expert database...
This paper examines the problem of adding non-deterministic constructs to a declarative database language based on Horn Clause Logic. We revise a previously proposed approach, the choice construct introduced by Krishnamurthy and Naqvi, from the viewpoints of amenability to efficient implementation and expressive power. Thus, we define a construct called dynamic choice, which is consistent with the...
An update specifies not only assumptions that are required for the current database, but also assertions that will hold in a new database. Queries are special cases of updates that contain assertions about only the current database. Inspired by connectives and quantifiers in queries, we develop an update calculus that extends relational calculus with assertions about a new database and a new connective,...
We develop a formal model to capture the evolution of method schemas, and obtain basic results on such evolutions. We use our model to obtain an algorithm for incremental consistency checking. The algorithm is optimal in the sense that it avoids any redundant checking.
Object-oriented database systems (ooDBMSs) are supposed to offer at least the functionality available in commercial relational DBMSs of today. One important consequence of this is that they have to provide a separation of the global (conceptual) database schema from the external schema (“subschema”) of a particular task. Views are a mechanism to realize this data independence. In addition, they also...
We identify a number of simple, syntactic properties of recursive subgoals in linear single-rule and two-rule Datalog programs. These properties can be recognized in linear time and provide a sufficient condition for uniform 1-boundedness of single-rule programs. They can also be used to characterize both uniform 1-boundedness for single-rule programs and 1-boundedness for two-rule programs, when...
We provide a general framework for declarative selection operations for complex object databases, based on the safe calculus for complex objects. Within this framework, we consider a class of “single pass-evaluable” selection operations. We show how such selection operations can be succinctly expressed by programs that use only very simple positive existential selections. Also, a syntactic criterion...
A sufficient condition is given for effective computability of a magic program, assuming that predicates satisfy some finiteness and monotonicity constraints. Effective computability means that a bottom-up evaluation is a finite process. This sufficient condition can show effective computability in cases that could not be handled by previous methods. Testing the condition is exponential in the arity...
The author will not pretend to be unbiased in the matter of comparing the deductive and object-oriented approaches to new database systems; he believes that despite some important concepts originating with the object-oriented approach, the deductive family of systems will ultimately dominate. We shall explore some of the reasons why the two approaches do not mix well. Fortunately, most of the features...
We study the problem of updating intensional relations in the framework of deductive databases on which integrity constraints (specifically functional dependencies) are defined. First, a formalization of a model-theoretic semantics of updates is provided: the notions of representability, consistency and determinism are introduced to characterize the various cases. Then, a proof-theoretic approach,...
This paper relates our experience in integrating constraint resolution into an object-oriented deductive system. We motivate this work by showing that disjunctive information and global constraints fit naturally in an object-oriented model and are actually necessary to perform common tasks. We identify three difficulties in developing such an extended object-oriented system (namely, compilation, domain...
Virtually all semantic or object-oriented data models assume objects have an identity separate from any of their parts. These models allow users to define complex object types in which property values may be any other objects. Often the query language allows a user to navigate from object to object by following a property value path. In this paper, we consider the combination of three forms of constraints...
In order to share persistent information among applications, one should provide specifications, which represent stored information and available operations. In addition to specifications, mechanism for viewing persistent information should be provided to applications. This paper proposes mechanisms for providing these abilities to applications and systems which deal with persistent information. The...
Many database applications require the storage and manipulation of different versions of data objects. However, current database systems do not support versioning well. Each application area treats versions in its own way, and these ways are usually incompatible with each other. We show how this incompatibility can be resolved by separating the physical, conceptual, and logical levels of versioning...
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