An approach to accommodating semantic heterogeneity in a federation of interoperable, autonomous, heterogeneous databases is presented. A mechanism is described for identifying and resolving semantic heterogeneity while at the same time honoring the autonomy of the database components that participate in the federation. A minimal, common data model is introduced as the basis for describing sharable information, and a three-pronged facility for determining the relationships between information units (objects) is developed. Our approach serves as a basis for the sharing of related concepts through (partial) schema unification without the need for a global view of the data that is stored in the different components. The mechanism presented here can be seen in contrast with more traditional approaches such as “integrated databases” or “distributed databases”. An experimental prototype implementation has been constructed within the framework of the Remote-Exchange experimental system.

ODE is a database system and environment based on the object paradigm. It offers one integrated data model for both database and general purpose manipulation. The database is defined, queried and manipulated in the database programming language O++ which is based on C++. O++ borrows and extends the object definition facility of C++, called the class. Classes support data encapsulation and multiple inheritance. We provide facilities for creating persistent and versioned objects, defining sets, and iterating over sets and clusters of persistent objects. We also provide facilities to associate constraints and triggers with objects. This paper presents the linguistic facilities provided in O++ and the data model it supports. 1. INTRODUCTION The object paradigm is a natural way of organizing data as it allows users to structure, retrieve and update data in terms of the application domain. ODE is a database system and environment based on the object paradigm. The database is defined, queri...

The Mneme project is an investigation of techniques for integrating programming language and database features to provide better support for cooperative, information-intensive tasks such as computer-aided software engineering. The project strategy is to implement efficient, distributed, persistent programming languages. We report here on the Mneme persistent object store, a funda-mental component of the project, discussing its design and initial prototype. Mneme stores objects in a simple and general format, preserving object identity and object interrelationships. Specific goals for the store include portability, extensibility (especially with respect to object management policies), and performance. The model of memory that the store aims at is a single, cooperatively-shared heap, distributed across a collection of networked computers. The initial prototype is intended mainly to explore performance issues and to support object-oriented persistent programming languages. We include performance measurements from the prototype as well as more qualitative results.

We describe the TIGUKAT objectbase management system that is under development at the Laboratory for Database Systems Research at the University of Alberta. TIGUKAT has a novel object model whose identifying characteristics include a purely behavioral semantics and a uniform approach to objects. Everything in the system, including types, classes, collections, behaviors, functions as well as meta-information, is a first-class object with well-defined behavior. In this way, the model abstracts everything, including traditional structural notions such as instance variables, method implementation and schema definition, into a uniform semantics of behaviors on objects. Our emphasis in this paper is on the object model, its implementation, the persistence model and the query language. We also (briefly) present other database management functions that are under development such as the query optimizer, the version control system and transaction manager.

Abstract. This paper studies the RDF model from a database perspective. From this point of view it is compared with other database models, particularly with graph database models, which are very close in motivations and use cases to RDF. We concentrate on query languages, analyze current RDF trends, and propose the incorporation to RDF query languages of primitives which are not present today, based on the experience and techniques of graph database research. 1

We give an axiomatic definition of the basic structure, called a class dictionary graph, used by object-oriented designers and programmers during the software development process. The contributions of this paper are twofold: An axiomatic foundation for objectoriented data modeling and efficient algorithms for checking whether a given data model satisfies the axioms. The presented data model is the foundation of a number of techniques for developing object-oriented systems including adaptive software, schema abstraction from object examples, schema optimization, planning techniques for system development, the Law of Demeter, etc. Keywords: Object-oriented data modeling and programming, algorithms and tools for objectoriented design, axioms for data models, Demeter Method. 1 Introduction In object-oriented data modeling and programming, each entity of the problem domain is represented by a set of objects with relations and operations. Each object is composed of part objects/su...

1 Introduction A Formal Temporal Object-Oriented Data Model Elisa Bertino Elena Ferrari Giovanna Guerrini snapshot tuple timestamping attribute timestamping bertino@hermes.mc.dsi.unimi.it, ferrarie@dsi.unimi.it guerrini@disi.unige.it Temporal databases are an active and fast growing research area. Although many extensions to the relational data model have been proposed in order to incorporate time, there is no comparable amount of work in the context of object-oriented data models. This paper presents Chimera, a temporal extension of the Chimera object-oriented data model. The main contribution of this work is to define a formal temporal object-oriented data model and to address on a formal basis several issues deriving from the introduction of time in an object-oriented context. Dipartimento di Scienze dell'Informazione - Universit`a di Milano Via Comelico, 39/41 - I20133 Milano, Italy Dipartimento di Informatica e Scienze dell'Informazione - Universit`a di Genova Vi...

Abstract | This paper tells the story of OQL, the standard query language of the Object Database Management Group (ODMG) [30]. The story starts in 1988, at INRIA in the Alta r Group y. The objective of that group was to develop an object-oriented database system [41]. This objective was reached: in September 1991 the O2 database system started its commercial career as the main product of a company called O2Technology [6]. As opposed to its competitors, O2 featured a full- edged query language named O2SQL [22]. The story goes on with the creation of the ODMG in 1991 and the adoption of O2SQL as the standard object query language under its new and nal name: OQL. During the following years, OQL went through some modi cations, the most important ofwhich resulted in OQL 1.2 that o ers some level of compliance with SQL92. On top of providing the expressive power of the SQL92 query language [54], OQL allows objects to be queried. This is a claim also supported by the upcoming SQL3. However, due to its adequacy to the object oriented type system and its functional nature, OQL is much simpler to learn, use and implement. A goal of this paper is to demonstrate this. This paper tells about the mistakes and pertinent choices we made while designing and implementing OQL. I hope it also conveys the great pleasure I had to be part of this adventure. Key words: Object-oriented database, query language 1.

Virtually all semantic or object-oriented data models assume objects have an identity separate from any of their parts, and allow users to define complex object types in which part values may be any other objects. In [20], a more general form of functional dependency is proposed for such models in which component attributes may correspond to descriptions of property paths, called path functional dependencies (PFDs). The main contribution of the reference is a sound and complete axiomatization for PFDs when databases may be infinite. However, a number of issues were left open which are resolved in this paper. We first prove that the same axiomatization remains complete if PFDs are permitted empty left-hand sides, but that this is not true if logical consequence is defined with respect to finite databases. We then prove that the implication problem for arbitrary PFDs is decidable. The proof suggests a means of characterizing an important function closure which is then used to derive an effective procedure for constructing a deterministic finite state automation representing the closure. The procedure is further refined to efficient polynomial time algorithms for the implication problem for cases in which antecedent PFDs are a form of complex key constraint. Index Terms: constraints, functional dependencies, object-oriented data models, complex objects, implication problems

Order-sorted equational logic is extended with dynamic logic to a specification language for dynamic objects. Special attention is paid to different concepts of encapsulation that play a role in object-orientation. It is argued that the resulting language, CMSL, meets those requirements of the object-oriented database system manifesto [6] that are applicable to object-oriented conceptual models (as opposed to OO databases).