Gerti Kappel

Object/behavior diagrams

A novel diagram technique is presented to depict the structure as well as the behavior of objects. One of its distinguishing characteristics is its strict adherence to the object-oriented paradigm. A first prototype of an editor for object/behavior diagrams has been developed and is running on SUN-workstations. To assist the user the editor provides hypertext style facilities for navigating through different diagrams. For example, by clicking on an activity in a life cycle diagram one moves to the activity specification diagram of that activity.<<ETX>>

USING AN OBJECT-ORIENTED DIAGRAM TECHNIQUE FOR THE DESIGN OF INFORMATION SYSTEMS

Abstract An object-oriented diagram technique is introduced for the design of information systems. Structural properties of objects are depicted in object diagrams. Dynamic properties are shown in behaviour diagrams. Object diagrams are based on semantic data model concepts. Behaviour diagrams are based on Petri nets and model the life cycles of objects through a set of states (places) and activities (transitions). The relationship between Object/Behaviour diagrams and Predicate/Transition nets is shown. The semantics of Object/Behaviour diagrams is formally defined through a mapping into Predicate/Transition nets.

Semantics of object-oriented data models — The evolving algebra approach

The formal description of the semantics of object-oriented data models is still an open problem. Some characteristic features of object-oriented data models, such as methods and inheritance, involve investigating data and schema. Therefore they can not be handled straightforwardly with first order logic. As an alternative, we propose the evolving algebra approach to specify the formal semantics of object-oriented data models. Evolving algebras provide a framework for defining the operational semantics of programming languages based on dynamic structures. In this paper we show how evolving algebras can be used in particular to define the operational semantics of object creation, of overriding and dynamic binding, and of inheritance at the type level (type specialization) and at the instance level (object specialization).

Local Referential Integrity

This paper introduces the concept of local referential integrity according to which an object may only reference objects belonging to the same composite object. For example, in production planning an employee of some department may only be scheduled to work on machines belonging to the same department. Usually, such a constraint must be stated explicitly by a predicate as “add on” to a database schema. Object-oriented data models have become popular for just the opposite. They represent implicitly integrity constraints which formerly had to be stated explicitly. Prominent examples, which so far have been studied independently, are referential integrity and composite objects. Local referential integrity combines both concepts by applying referential integrity within a composite object. We show that local referential integrity can be represented easily within an object-oriented database schema by using “local object classes” as domains of relationships. A local object class is a set of objects belonging exclusively to some composite object. Local referential integrity is maintained if any relationship from within a composite object to one of its local classes references a current member of that class.

State of art and open issues on graphical user interfaces for object-oriented database systems

Abstract Graphical user interfaces have become very popular for database systems because they increase the usability of these applications. The functionality and ease-of-use of the graphical user interface, however, depend on the expressiveness and complexity of the underlying data model. With the advent of new database technology based on powerful data models like the object-oriented data model, new challenges and new opportunities are posed in user interface design. In the paper critical issues of graphical user interface development for object-oriented database systems are discussed.

Inheritance of Object Behavior — Consistent Extension of Object Life Cycles

Inheritance is one of the most prominent features of object-oriented design. Object types are organized in hierarchies in which subtypes inxad herit the structure as well as the behavior of supertypes. As inheritance of behavior is concerned, the discussion has mainly focused on inheritance of single activities in the past. Object behavior, however, is specified at two interrelated levels of detail: at the activity level and at the obxad ject type level. The latter is specified in terms of object life cycles that identify legal sequences of states and activities. In this paper we treat inheritance of object life cycles in the realm of Behavior Diagrams, which are based on Petri nets. A behavior diagram of an object type models the possible life cycles of its instances by states, activities, and arcs corresponding to places, transitions, and arcs of Petri nets. In an inheritance hierarchy, subtypes usually specialize supertypes in two ways: by extension and by refinement. For Behavior Diagrams, extension means adding activities, states, and arcs; and refinement means expanding activities and states in subnets. The main contribution of this paper is a set of sufficient and necessary conditions to check whether a behavior diagram B consistently extends another behavior diagram B.

Reorganizing Object Behavior by Behavior Composition — Coping with Evolving Requirements in Office Systems

Office systems are typical representatives of applications with evolving requirements. The functionality of office systems must reflect, for example, organizational changes, new laws, and work flow optimizations. Since an application should not be rebuilt from scratch every time requirements change, reorganization mechanisms and tools supporting application evolution are needed.

Object-Oriented Analysis and Design — A Case Study

Several methods for object-oriented system development have been published by the scientific community. Recently, industrial software developers are also attracted by the object-oriented paradigm and consider switching from structured techniques to an object-oriented approach to system development. A question commonly asked by industry is, how both approaches compare on industrial applications. To investigate on this issue, a case study has been undertaken.

Form Flow Systems Based on NF2-Relations

In this paper it will be shown that a conceptual model based on nonfirst-normal-form (NF2) relations is well suited for applications in the area of form flow systems. A decomposition technique of NF2-relations is introduced which allows a semantic interpretation of the decomposed relations in an easy way.

Einleitung und Motivation

Informationssysteme haben in den letzten Jahren an Bedeutung gewonnen. Wurden sie fruher fast ausschlieslich im betriebswirtschaftlich administrativen Bereich eingesetzt, so sind sie heute auch aus dem technischen Anwendungsbereich (Computer Aided Design, Computer Integrated Manufacturing, um nur einige Schlagworte zu nennen) kaum wegzudenken. Informationssysteme sind datenintensive Softwaresysteme, d. H. sie stellen die Funktionalitat zur Verwaltung und Manipulation groser Mengen von Daten zur Verfugung und bauen daher in der Regel auf einem Datenbanksystem auf. In diesem Sinne bauen Informationssysteme auch auf einem Beschreibungsmodell, traditionell auch Datenmodell genannt, auf, das es erlaubt, den jeweils abzubildenden Problembereich so realitatsnah wie moglich zu spezifizieren. Neue Anforderungen an diese Beschreibungsmodelle sind u.a. die Modellierung von komplex strukturierten Daten, wie sie vor allem in technischen Anwendungen anzutreffen sind, und die Modellierung von dynamischer Information zusatzlich zu und gemeinsam mit den statischen Datenstrukturen. Eine Antwort auf diese Anforderungen sind objektorientierte Informationssysteme, d.h. Informationssysteme basierend auf einem objektorientierten Beschreibungsmodell.