An experience modelling telecommunications systems using ODP-DLcomp

Abstract

Abstract. The ODP-DLcomp language is intended to describe systems in the ODP computational model. It is object-oriented, implementation-independent and its formal semantics are based on LOTOS, thus it is a Formal Description Technique. It supports specification of interface and object templates, with appropriate creation and binding operations. An application of the language is demonstrated using the Plain Old Telephone System example.Keywords: Open Distributed Processing, OO Languages, Specification, Telephony IntroductionODP-DLcomp was designed and implemented at GMD-FOKUS by Frank Koch [Koch94]. The first author participated in the group at the time.The motivation behind this new language was to offer a more readable and compact alternative to the LOTOS description of the ODP computational model [Vog93] but also to offer a bridge between Formal Description Techniques and Object Oriented implementation languages.In this paper, we show that ODP-DLcomp includes all the essential concepts for system definition in the ODP computational model. It is high-level and object-based. One of its important characteristics is that its semantics are defined in terms of the formal language LOTOS[BoBr87] [LoFH92]. In fact, the definition is constructive and a prototype compiler from ODP-DLcomp into LOTOS is available. Thus, the language has all the essential characteristics required of a Formal Description Technique for ODP. Because of their capability of being compiled into a language that is at least partially executable, specifications written in ODP-DLcomp constitute a prototype of the system being specified. Activities such as validation and test case generation, possible from LOTOS specifications, therefore are also possible from ODP-DLcomp specifications.This language is somewhat comparable to TINA ODL [TINAC94], however the latter is not formal, and does not offer the capability of behavior specification.A brief introduction to the language is given, followed by an example of its use for the description of a Plain Old Telephone System. Basic concepts of ODP computational modelThe ODP computational viewpoint provides the concepts needed to explain how services can be programmed in a form suitable for distribution [FLM95]. This viewpoint focuses on the organization of applications in architecturally conformant ways rather than on the mechanisms used to distribute or support the applications in the system. The ODP com-2 putational model is the abstract model to express the concepts of the computational viewpoint. It is a framework for describing the structure, specification and execution of the (components of the) distributed application on the distributed computing platform. It describes the coarse-grained structure of an application, i.e., the application components and their interaction at an abstract, system independent level. Each coarse-grained entity of a distributed application is represented by an object, called computational object, with a (set of) well defined interface(s), called computational interface(s). Th...