Jos Warmer

Object Modeling with the OCL

With the move towards UML becoming a family of modelling languages, there is a need to view the Object Constraint Language in the same light. The aim of this paper is to identify a meta-modelling facility that encompasses the specification of the semantics of a family of object constraint languages. This facility defines a common set of model concepts, semantic domain concepts and semantic mappings that can be conveniently reused when constructing new family members.

Extending OCL to include actions

The UMLs Object Constraint Language provides the modeller of object-oriented systems with ways to express the semantics of a model in a precise and declarative manner. The constraints which can be expressed in this language, all state requirements on the static aspects of the system. The Object Constraint Language currently lacks a way to express that events have happened or will happen, that signals are or will be send, or that operations are or will be called. This paper introduces an extension to OCL to solve the above problem: the so-called action clause. We describe how this extension is integrated with the UML semantics to avoid semantics overlap. It also shows that a modeler can use it to specify dynamic requirements declaratively on an abstract level, without the need to use full operational dynamic diagrams.

The Amsterdam Manifesto on OCL

In November 1998 the authors participated in a two-day workshop on the Object Constraint Language (OCL) in Amsterdam. The focus was to clarify issues about the semantics and the use of OCL, and to discuss useful and necessary extensions of OCL. Various topics have been raised and clarified. This manifesto contains the results of that workshop and the following work on these topics. Overview of OCL.

Defining UML family members using prefaces

The Unified Modeling Language is extensible, and so can be regarded as a family of languages. Implicitly or explicitly, any particular UML model should be accompanied by a definition of the particular UML family member used for the model. The definition should cover syntactic and semantic issues. This paper proposes a mechanism for associating models with such definitions. Any particular definition would form what we call a preface. The name is intended to suggest that the definition of a particular UML family member must conceptually come before any model built using that family member. A preface would be large, and should be organised using packages. This would allow large amounts of sharing between different prefaces. The paper proposes that prefaces should have an axiomatic style of semantics, through not necessarily fully formal, and it offers a general approach to semantics that would reduce problems of inconsistency within a large preface, based on the idea of general cases and special cases.

Informal Formality? The Object Constraint Language and Its Application in the UML Metamodel

Within the field of object technology it is becoming recognised that constraints are a good way to produce more precise and formal specifications than with diagrams alone. Evidence of this is that UML incorporates a standard constraint language called OCL (Object Constraint Language). The availability of OCL will encourage UML users to add constraints to their UML models. This paper explains OCL and demonstrates its applicability. Probably the largest application of OCL to date was its use to define the metamodel of UML, and the experiences gained in this application are discussed.

Defining the context of OCL expressions

Expressions written in Object Constraint Language (OCL) within a UML model assume a context, depending upon where they are written. Currently the exact nature of this context is not fully defined. Furthermore there is no mechanism for defining the context for OCL expressions in extensions to UML. This paper defines the context of OCL expressions, and proposes precise and flexible mechanisms for how to specify this context.

Tool support for OCL and related formalisms – needs and trends

The recent trend in software engineering to model-centered methodologies is an excellent opportunity for OCL to become a widely used specification language. If the focus of the development activities is shifted from implementation code to more abstract models then software developers need a formalism to provide a complete, unambiguous and consistent model at a very detailed level. OCL is currently the only language that can bring this level of detail to UML models. The purpose of the workshop was to identify future challenges for OCL and to discuss how OCL and its current tool support can be improved to meet these challenges. The workshop gathered numerous experts from academia and industry to report on success stories, to formulate wishes to the next generation of OCL tools, and to identify weaknesses in the language, which make OCL sometimes cumbersome to use. The workshop could also attract numerous people whose aim was to get an overview on the state of the art of OCL tool support and on how OCL can efficiently be applied in practice.

Mod4J: a qualitative case study of model-driven software development

Model-driven software development (MDSD) has been on the rise over the past few years and is becoming more and more mature. However, evaluation in real-life industrial context is still scarce. In this paper, we present a case-study evaluating the applicability of a state-of-the-art MDSD tool, MOD4J, a suite of domain specific languages (DSLs) for developing administrative enterprise applications. MOD4J was used to partially rebuild an industrially representative application. This implementation was then compared to a base implementation based on elicited success criteria. Our evaluation leads to a number of recommendations to improve MOD4J. We conclude that having extension points for hand-written code is a good feature for a model driven software development environment.

Making UML activity diagrams object-oriented

The way the activity diagram in the Unified Modeling Language is currently defined is not object-oriented. Activity diagrams specify data/object flow. We feel that the object-oriented principles should hold for every part of the standard for object-oriented analysis and design. Therefore this paper proposes a few small changes to the UML metamodel that will integrate activity diagrams into an object-oriented scheme, focusing on three fundamental object-oriented principles: responsibility, information hiding/encapsulation, and delegation.

OCL for (meta-)models in multiple application domains

The workshop OCLApps 2006 was organized as a part of MoDELS/UML Conference in Genova, Italy. It continues the series of five OCL (Object Constraint Language) workshops held at previous UML/MoDELS conferences between 2000 - 2005. Similar to its predecessors, the workshop addressed both people from academia and industry. The advent of the MDA (Model Driven Architecture) vision and the rapid acceptance of MDE (Model Driven Engineering) approaches emphasize new application domains (like Semantic Web or Domain Specific Languages) and call for new OCL functionalities. In this context, the OCLApps 2006 Workshop, was conceived as a forum enabling researchers and industry experts to present and debate how the OCL could support these new requirements.