Maarten Steen

COSMO: A conceptual framework for service modelling and refinement

This paper presents a conceptual framework for service modelling and refinement, called the COSMO (COnceptual Service MOdelling) framework. This framework provides concepts to model and reason about services, and to support operations, such as composition and discovery, which are performed on them at design and run-time. In particular, the framework should facilitate the use of different service description languages tailored to different service aspects, such as the behaviour of a service and the information it manipulates, or design tasks, such as modelling, analysis and implementation. The idea is that models produced by these languages can be mapped onto the concepts of the framework, thereby facilitating one to relate these models, e.g., to verify consistency. Therefore, a requirement on the framework is to provide concepts that capture all elementary and generic service properties that are relevant during the service development process. We capture these properties by analysing existing service definitions and from earlier experience. Furthermore, we want the same concepts to be applicable throughout the service development process when modelling and refining services at successive abstraction levels. The framework distinguishes three generic abstraction levels, and describes an approach to assess the conformance between the service models produced at these abstraction levels.

Viewpoint consistency in ODP

Open Distributed Processing (ODP) is a joint ITU/ISO standardisation framework for constructing distributed systems in a multi-vendor environment. Central to the ODP approach is the use of viewpoints for specification and design. Inherent in any viewpoint approach is the need to check and manage the consistency of viewpoints. In previous work we have described techniques for consistency checking, refinement, and translation between viewpoint specifications, in particular for LOTOS and Z/Object-Z. Here we present an overview of our work, motivated by a case study combining these techniques in order to show consistency between viewpoints specified in LOTOS and Object-Z.

A Formal Framework for Viewpoint Consistency

Multiple Viewpoint models of system development are becoming increasingly important. Each viewpoint offers a different perspective on the target system and system development involves parallel refinement of the multiple views. Viewpoints related approaches have been considered in a number of different guises by a spectrum of researchers. Our work particularly focuses on the use of viewpoints in Open Distributed Processing (ODP) which is an ISO/ITU standardisation framework. The requirements of viewpoints modelling in ODP are very broad and, hence, demanding. Multiple viewpoints, though, prompt the issue of consistency between viewpoints. This paper describes a very general interpretation of consistency which we argue is broad enough to meet the requirements of consistency in ODP. We present a formal framework for this general interpretation; highlight basic properties of the interpretation and locate restricted classes of consistency. Strategies for checking consistency are also investigated. Throughout we illustrate our theory using the formal description technique LOTOS. Thus, the paper also characterises the nature of and options for consistency checking in LOTOS.

Supporting viewpoint-oriented enterprise architecture

Increasingly, organisations establish what is called an enterprise architecture. The enterprise architecture combines and relates all architectures describing some aspect of the organization, such as the business process architecture, the information architecture, and the application architecture. It is a blueprint of the organisation, which serves as a starting point for analysis, design and decision making. Viewpoints define abstractions on the set of models representing the enterprise architecture, each aimed at a particular type of stakeholder and addressing a particular set of concerns. The use of viewpoints is widely advocated for managing the inherent complexity in enterprise architecture. Viewpoints can both be used to view certain aspects in isolation, and for relating two or more aspects. However, in order to make such a viewpoint-oriented approach practically feasible, architects require a tool environment, which supports the definition, generation, editing and management of architectural views. Moreover, such an environment should work in concert with existing domain-specific modelling tools. We present the design of such a tool environment for viewpoint-oriented enterprise architecture.

ODP enterprise viewpoint specification

Abstract The Open Distributed Processing (ODP) standardisation initiative has led to a framework by which distributed systems can be modelled using a number of viewpoints. These include an enterprise viewpoint, which focuses on the objectives and policies of the enterprise that the system is meant to support. Although the ODP reference model provides abstract languages of relevant concepts, it does not prescribe particular techniques that are to be used in the individual viewpoints. In particular, there is a need to develop appropriate notations for ODP enterprise specification, in order to increase the applicability of the ODP framework. In this paper, we tackle this concern and develop a specification language to support the current draft of the enterprise viewpoint. In doing so, we analyse the current definition of the ODP enterprise viewpoint language. Using the Unified Modelling Language ( uml ), a meta-model of the core concepts and their relationships is constructed, and we also investigate to what extent the uml can be used for enterprise viewpoint specification. We, then, focus on the expression of enterprise policies that govern the behaviour of enterprise objects. We develop a policy language, which is a combination of structured English and simple predicate logic and is built on top of the formal object-oriented specification language Object-Z, into which the complete language is translated. We illustrate the ideas in the paper with a case study that presents an enterprise specification of a library support system.

FDTs for ODP

Abstract This paper discusses the use and integration of formal techniques into the Open Distributed Processing (ODP) standardization initiative. The ODP reference model is a natural progression from OSI. Multiple viewpoints are used to specify complex ODP systems. Formal methods are playing an increasing role within ODP. We provide an overview of the ODP reference model, before discussing the ODP requirements on FDTs, and the role such techniques play. Finally, we discuss the use of formalisms in the central problem of maintaining cross viewpoint consistency.

Reusable Model Transformation Patterns

This paper is a reflection of our experience with the specification and subsequent execution of model transformations in the QVT core and Relations languages. Since this technology for executing transformations written in high-level, declarative specification languages is of very recent date, we observe that there is little knowledge available on how to write such declarative model transformations. Consequently, there is a need for a body of knowledge on transformation engineering. With this paper we intend to make an initial contribution to this emerging discipline. Based on our experiences we propose a number of useful design patterns for transformation specification. In addition we provide a method for specifying such transformation patterns in QVT, such that others can add their own patterns to a catalogue and the body of knowledge can grow as experience is built up. Finally, we illustrate how these patterns can be used in the specification of complex transformations.

Formalising ODP enterprise policies

The open distributed processing (ODP) standardisation initiative has led to a framework by which distributed systems can be modelled using a number of viewpoints. These include an enterprise viewpoint, which focuses on the objectives and policies of the enterprise that the system is meant to support. Although the ODP reference model provides abstract languages of relevant concepts, it does not prescribe particular techniques that are to be used in the individual viewpoints. In particular, there is a need to develop appropriate notations for ODP enterprise specification, in order to increase the applicability of the ODP framework. In this paper, we tackle this concern and develop a specification language to support the enterprise viewpoint. In doing so, we focus on the expression of enterprise policies that govern the behaviour of enterprise objects. The language we develop is a combination of structured English and simple predicate logic, and is built on top of the formal object-oriented specification language Object-Z. We illustrate its use with a case study that presents an enterprise specification of a library support system.

Viewpoint consistency in ODP, a general interpretation

Multiple viewpoints are used in Open Distributed Processing (ODP) in order to decompose the complexity inherent in specifying distributed systems. Multiple viewpoints prompt the issue of consistency between viewpoints. The ODP reference model alludes to three different interpretations of consistency. This paper responds to this uncertainty by proposing a single all embracing interpretation of consistency. We show that our interpretation, firstly, satisfies all the basic requirements of a definition of consistency and, secondly, can be specialised to any of the three ODP reference model definitions. The generality of our definition will be illustrated through instantiation in the FDT LOTOS.

Constructive consistency checking for partial specification

Partial specification is a method of specifying complex systems in which the system is described by a collection of specifications, each approaching the system from a different viewpoint. The specification notation Z is often advocated as a suitable language for this style of specification. For collections of partial specifications to be meaningful, they need to be consistent, i.e. they should not impose contradictory requirements. This paper addresses how the consistency between partial specifications in Z can be checked, by constructing unifications, i.e. least common refinements, of viewpoint specifications.