Role change in database domains

In data modelling the universe of discourse (UoD) is divided up into classes having a taxonomic structure which is intended to express some of the structure inherent in the UoD. Some of these classes. for example the class of persons or departments, may be called "natural kinds," in that they are a fixed set of possible objects, existing in some possible state of the UoD, and all of which have a similar structure and behavior. Others have a more dynamic nature, such as the class of stu­ dents. Whereas an object is created as as person and, when it ceases to be a person, ceases to exist, an object may come to be a student and cease to be one without com­ ing into existence or passing away. A class like persons is a natural kind, and a class like students will be called roles in this report. This report studies the formal defini­ tion of roles and the resulting taxonomy of natural kinds and roles

MODELING DYNAMICS OF DATABASES WITH RELATIONAL DISCRETE EVENT SYSTEMS AND MODELS

Behavior of relational databases is studied within the framework of Relational Discrete Event Systems (RDESes) and Models (RDEMs). Three behavior specification methods based on production systems, recurrence equations, and Petri nets are defined and their expressive powers are compared. Production system RDEM is extended to support non-determinism, and various deterministic and non-deterministic production system interpreters are introduced and formally compared in terms of their expressive power. It is shown that the parallel deterministic interpreter has more expressive power than other interpreters including an OPS5-like interpreter. Since it is also parallel, this makes the parallel deterministic interpreter a very attractive interpreter for production systems.Information Systems Working Papers Serie

Axiomatic Specification of Database Domain Statics

In the past ten years, much work has been done to add more structure to database models 1 than what is represented by a mere collection of flat relations (Albano & Cardelli [1985], Albano et al. [1986], Borgida eta. [1984], Brodie [1984], Brodie & Ridjanovic [1984], Brodie & Silva (1982], Codd (1979], Hammer & McLeod (1981], King (1984], King & McLeod [1984], [1985], Mylopoulos et al. [1980], Smith & Smith 1977a & b). 2 The informal approach which most of these studies advocate has a number of disadvantages. First, a recent survey of some of the pro­ posed models by Urban & Delcambre [1986] reveals a wide divergence in terminology and con­ cepts, making comparison of the expressive power of these models difficult. Second, undefined or even ill-defined concepts are a hindrance, not an aid, for the analysis of the Universe of Discourse (UoD). Third, informal treatment 9f such complex structures as set hierarchies, gen­ eralization hierarchies and aggregation hierarchies all in one model, with some dynamics thrown in for good measure, bodes ill for the consistency of these theories. The first goal of the research reported on is to integrate the static structures which these models propose in one coherent, axiomatic framework. It will be shown in chapter 7 that the theory presented here provides the needed conceptual foundations for these models. A second aim is to provide a possible worlds framework onto which to graft theories of the dynamics of the UoD. The third aim is to provide clear concepts which can aid the database model designer in his or her thinking about the UoD. In this report we concentrate on the first goal only, leav­ ing the formulation of theories of domain dynamics and the application to system development as research goals for the near future

Making object-oriented databases more knowledgeable (From ADAM to ABEL)

Tesis leida en la Universidad de Aberdeen. 178 p.The salient points of this thesis are as follows: • Object-Oriented Databases can help in solving the impedance mismatch problem by introducing methods. However, methods have sometimes been overused in the sense th at the code encapsulated refers not only to how the operation is implemented but also to other kinds of knowledge that are implicit in the code. The disadvantages of this approach for modelling integrity constraints, user-defined relationships and active behaviour are pointed out. • The ADAM Object-Oriented Database has been extended to allow the designer to specify integrity constraints declaratively. A constraint equation approach is implemented th at supports the inheritance of constraints. • A need for semantic-rich user-defined relationships has been identified. In this thesis, relationships are represented as objects. An approach to enhance the semantics of relationships in both its structural and behavioural aspects is presented. The most novel idea of the approach presented is the support of the inferred properties and the operational semantics of relationships. • Active Databases have recently become an im portant area of research. This thesis shows how to extend an Object-Oriented Database with active capabilities. The principal contribution lies in representing as ‘first-class’ objects not only the active rules but also the rule manager itself. Hence, besides handling active rules as any other object in the system, future requirements can be supported just by specialising the current rule manager. • Active rules have been proposed for several purposes. Several examples, are given of the direct use of rules. However, higher level tools can be provided of which rule

Relationship analysis : improving the systems analysis process

A significant aspect of systems analysis involves discovering and representing entities and their inter-relationships. Guidelines exist to identify entities but do not provide a rigorous and comprehensive process to explicitly capture the relationship structure of the problem domain. Whereas, other analysis techniques lightly address the relationship discovery process, Relationship Analysis is the only systematic, domain-independent analysis technique focusing exclusively on a domain\u27s relationship structure. The quality of design artifacts, such as class diagrams, and development time necessary to generate these artifacts can be improved by first representing the complete relationship structure of the problem domain. The Relationship Analysis Model is the first theory-based taxonomy to classify relationships. A rigorous evaluation was conducted, including a formal experiment comparing novice and experienced analysts with and without Relationship Analysis. It was shown that the Relationship Analysis Process based on the model does provide a fuller and richer systems analysis, resulting in improved quality of and reduced time in generating class diagrams. It also was shown that Relationship Analysis enables analysts of varying experience levels to achieve a similar level of quality of class diagrams. Relationship Analysis significantly enhances the systems analyst\u27s effectiveness, especially in the area of relationship discovery and documentation resulting in improved analysis and design artifacts

On the Utilisation of Persistent Programming Environments

There is a growing gap between the supply and demand of good quality software, which is primarily due to the difficulty of the programming task and the poor level of support for programmers. Programming is carried out using software tools which do not match very well either real world understanding of a problem or even the other tools which need to be used. In every phase of software production, the programmer must master new tools which function in a different way from each other. The Persistent Programming Paradigm attempts to reduce these problems by providing a programming environment which gives consistent methods of accessing program values of various kinds. Long-term and short-term data are treated in the same way. Numbers, text, graphical values and even program objects are all referred to in the same consistent way. Languages which support persistence provide considerable power within a simple environment, so that programmers can perform most if not all parts of the programming task in a coherent and uniform manner. This thesis tests the hypothesis that programmers do in fact derive some benefit from this - the simplification of the program and faster implementation of complex programs. The persistent language PS-algol is introduced and used to build: user-interface and compiler tools; a database application; some data modelling tools, both relational and semantic; a rapid prototyping system; an object-oriented language; and software support systems. In doing so, the thesis demonstrates the breadth of work which can be achieved using a Persistent Programming Language, and the ease with which these various projects can be implemented. Further, the thesis derives the beginnings of a methodology for using such a language and analyses how PS-algol could be improved. In doing so, the work aims to put the Persistent Programming Paradigm on a firm basis following significant use and experimentation

P-Pascal : a data-oriented persistent programming language

Bibliography: pages 187-199.Persistence is measured by the length of time an object is retained and is usable in a system. Persistent languages extend general purpose languages by providing the full range of persistence for data of any type. Moreover, data which remains on disk after program termination, is manipulated in the same way as transient data. As these languages are based on general purpose programming languages, they tend to be program-centred rather than data-centred. This thesis investigates the inclusion of data-oriented features in a persistent programming language. P-Pascal, a Persistent Pascal, has been designed and implemented to develop techniques for data clustering, metadata maintenance, security enforcement and bulk data management. It introduces type completeness to Pascal and in particular shows how a type-complete set constructor can be provided. This type is shown to be a practical and versatile mechanism for handling bulk data collections in a persistent environment. Relational algebra operators are provided and the automatic optimisation of set expressions is performed by the compiler and the runtime system. The P-Pascal Abstract Machine incorporates two complementary data placement strategies, automatic updating of type information, and metadata query facilities. The protection of data types, primary (named) objects and their individual components is supported. The challenges and opportunities presented by the persistent store organisation are discussed, and techniques for efficiently exploiting these properties are proposed. We also describe the effects on a data-oriented system of treating persistent and transient data alike, so that they cannot be distinguished statically. We conclude that object clustering, metadata maintenance and security enforcement can and should be incorporated in persistent programming languages. The provision of a built-in, type-complete bulk data constructor and its non-procedural operators is demonstrated. We argue that this approach is preferable to engineering such objects on top of a language, because of greater ease of use and considerable opportunity for automatic optimisation. The existence of such a type does not preclude programmers from constructing their own bulk objects using other types - this is but one advantage of a persistent language over a database system