In many class-based object-oriented systems the association between an instance and a class is exclusive and permanent. Therefore these systems have serious difficulties in representing objects taking on different roles over time. Such objects must be reclassified any time they evolve (e.g., if a person becomes a student and later an employee). Class hierarchies must be planned carefully and may grow exponentially if entities may take on several independent roles. The problem is even more severe for object-oriented databases than for common object-oriented programming. Databases store objects over longer periods, during which the represented entities evolve. This article shows how class-based object-oriented systems can be extended to handle evolving objects well. Class hierarchies are complemented by role hierarchies, whose nodes represent role types an object classified in the root may take on. At any point in time, an entity is represented by an instance of the root and a...

The duality of objects and relationships is so deeply embedded in our thinking that almost all modelling languages include it as a fundamental distinction. Yet there is evidence that the two are naturally complemented by a third, equally fundamental notion: that of roles. Although definitions of the role concept abound in the literature, we maintain that only few are truly original, and that even fewer acknowledge the intrinsic role of roles as intermediaries between relationships and the objects that engage in them. After discussing the major families of role conceptualizations, we present our own basic definition and demonstrate how it naturally accounts for many modelling issues, including multiple and dynamic classification, object collaboration, polymorphism, and substitutability. <3 2000 Elsevier Science B.V. All rights reserved.

In this paper, we argue that object-oriented models must be able to represent three kinds of taxonomic structures: static subclasses, dynamic subclasses and role classes. If CAR is a static subclass of V EHICLE, then a vehicle that is not a car can never migrate to the CAR subclass. If EMP loyee is a dynamic subclass of PERSON , then a PERSON that is not an employee may migrate to EMP . In both cases, an instance of the subclass is identical to an instance of the superclass. Finally, if EMP is modeled as a role class of PERSON every employee differs from every person, but a PERSON instance can acquire one or more EMP instances as roles. We outline an approach to formalizing these taxonomic structures in order-sorted dynamic logic with equality. Keywords: Theoretical foundations, formal methods, OO analysis and design February 2, 1994 Contents 1 Introduction 1 2 Methodological aspects of role-playing and class migration 1 2.1 Object classification and identification : : : : : : : : :...

In this paper we investigate several concepts that are known in database research for some time but which are still surrounded by some confusion. We start with the concepts of object identifier, surrogate and key and list the differences between these concepts, which in practice are often ignored. Sharpening these differences allows us to analyze the distinction between objects and roles that recently surfaced in the literature. Distinguishing objects from roles helps to avoid migration of objects between classes and thus the problems associated with it. We show that this distinction requires the use of role identifiers that, just as object identifiers, should be globally unique and unchangeable. We next show that using role identifiers requires a distinction between two essentially different kinds of inheritance relationships, is-a inheritance and played-by inheritance. These are often both treated as if they were one and the same kind of is-a relationship. The result of the discussio...

Object-oriented databases (OODBs) are believed to more naturally reflect the behavior and organization of complex application domains. The schema consists of a collection of classes, organized into hierarchies which nicely organize abstractions over the domain. Objects are created as instances of classes, encapsulating data and interpretation of data together. An important characteristic is the support for evolutionary programming, and so that existing programs may be extended with new classes without affecting other parts of the system.

This paper presents a semantic foundation of temporal conceptual models used to design temporal information systems. We consider a modelling language able to express both timestamping and evolution constraints. We conduct a deeper investigation of evolution constraints, eventually devising a model-theoretic semantics for a full-fledged model with both timestamping and evolution constraints. The proposed formalization is meant both to clarify the meaning of the various temporal constructors that appeared in the literature and to give a rigorous definition, in the context of temporal information systems, to notions like satisfiability, subsumption and logical implication. Furthermore, we show how to express temporal constraints using a subset of first-order temporal logic, i.e. DLRUS, the description logic DLR extended with the temporal operators Since and Until. We show how DLRUS is able to capture the various modelling constraints in a succinct way and to perform automated reasoning on temporal conceptual models.

ADOME, ADvanced Object Modeling Environment, an approach to integrating data and knowledge management based on object-oriented technology, is presented. Next generation information systems will require more flexible data modelling capabilities than those provided by current object-oriented DBMSs. In particular, integration of data and knowledge management capabilities will become increasingly important. In this context, ADOME provides versatile role facilities that serve as "dynamic binders" between data objects and production rules, thereby facilitating flexible data and knowledge management integration. A prototype that implements this mechanism and the associated operators has been constructed on top of a commercial object-oriented DBMS and a rule base system. Index Terms: Object modeling, knowledge semantics, dynamic roles, object-oriented databases, nextgeneration information systems 1 Introduction Increasingly, organizations require more intelligent information management. In o...

In this paper, concepts of deputy objects and deputy classes for object-oriented databases (OODBs) are introduced. They can be used for unified realization of object views, roles and migration. The previous researches on these concepts were carried out separately, although they are very closely related. Objects appearing in a view can be regarded as playing roles in that view. Object migration is caused by change of roles of an object. Deputy objects can be used for unified treatment of them and generalization of these concepts. The schemata of deputy objects are defined by deputy classes. A set of algebraic operations are developed for deputy class derivation. In addition, three procedures for update propagation between deputy objects and source objects have been designed, which can support dynamic classification. The unified realization of object views, roles and migration by deputy mechanisms can achieve the following advantages. (1) Treating view objects as roles of an object allows them to have additional attributes and methods so that the autonomous views suitable for OODBs can be realized. (2) Handling object roles in the same way as object views enables object migration to be easily realized by dynamic classification functions of object views. (3) Generalization of object views, roles and migration makes it possible that various semantic constraints on them can be defined and enforced uniformly.

The notion of object evolution covers several aspects being important for object-oriented information systems. An object keeps its identity (and some of its properties, of course) while changing its external interface and the implementation of its methods. We present a framework based on a temporal logic where the specification of an object template may be modified during system runtime. The presented extended temporal logic dyOSL explicitly manipulates state-dependent sets of current axioms. This framework can handle several problems arising with object evolution. 1 Introduction Conceptual modeling of information systems has successfully adopted the object paradigm as foundation for modeling techniques. However, many approaches are based on more or less informal frameworks influenced by object-oriented analysis and design [Boo91, CY90, RBP + 90]. But the aim of the conceptual modeling process is an exact and unambiguous, i.e. formal, description of the Universe of Discourse. Only a...

Business Artifacts are the core entities used by businesses to record information pertinent to their operations. Business operational models are representations of the processing of business artifacts. Traditional process modeling approaches focus on the actions taken to achieve a certain goal (verb-centric). Business artifact-centric modeling starts by identifying what is acted upon (noun-centric), and constructs business operational models by identifying the tasks/actions that business actors execute to add business value. In this paper, we identify important classes of properties on artifact-centric operational models. In particular, we focus on persistence, uniqueness and arrival properties. To enable a static analysis of these properties, we propose a formal model for artifact-centric operational models. We show that the formal model guarantees persistence and uniqueness. We prove that, while checking an arrival property is undecidable in general, under a restricted version of the formalism, an arrival property can be checked in EXPTIME. 1