Abstract—UML is a collection of notations for capturing a software system specification. These notations have a specific syntax defined by the Object Management Group (OMG), but many of their constructs only present informal semantics. They are primarily graphical, with textual annotation. The inadequacies of standard UML as a vehicle for complete specification and implementation of real-time embedded systems has led to a variety of competing and complementary proposals. The Real-time UML profile (UML-RT), developed and standardized by OMG, defines a unified framework to express the time, scheduling and performance aspects of a system. We present in this paper a framework approach aimed at deriving a complete specification of a real-time system. Therefore, we combine two methods, a semi- formal one, UML-RT, which allows the visual modeling of a real- time system and a formal one, CSP+T, which is a design language including the specification of real-time requirements. As to show the applicability of the approach, a correct design of a real-time system with hard real time constraints by applying a set of mapping rules is obtained. Keywords—CSP+T, formal software specification, process algebras, real-time systems, Unified Modeling Language. I. INTRODUCTION ML-RT [1] is an industrial standard used to model real- time systems but its modeling entities and syntactic constructions lack of a defined syntax and a precise semantics. In order to unambiguously specify the behavior of a reactive system, we have established a mapping that gives to UML-RT entities a defined meaning according to the semantic domain discussed in the following text. This work is aimed at obtaining a systematic, formal oriented, analysis and design method, which also includes temporal specifications. A set of rules allows us to systematically deriving a verifiable design of a real-time system from a semi-formal system requirements UML-RT model. CSP+T [2], which is an extension of CSP [3], [4], is a good candidate to give a precise semantics to UML-RT Manuscript received received July 15, 2005. This work is supported in part by the Spanish Ministry of Education and Science under Grant MAT2004-06872-C03-03. Kawtar Benghazi Akhlaki is a PhD candidate in the Departamento de Lenguajes y Sistemas Informáticos. Universidad de Granada, Granada 18071, Spain; e-mail: kawtar@ correo.ugr.es. Manuel I. Capel, is in the Universidad de Granada, where he studied Physics, obtained the MSC degree in 1982 and the PhD in Computer Science in 1992. He worked in the Universidad de Murcia before moving in 1989 to the Universidad de Granada where he is now leading a research group in the field of Concurrent Systems. His e-mail address is: mcapel@ugr.es and his Web-page can be found at http://lsi.ugr.es/~mcapel (Ph: 0034958242816, Fax: 0034958243179). analysis entities. On one part, UML-RT provides a visual system description of each object within the analysis model as well as its behaviour, which is diagrammatically represented by a Statecharts diagram [5]. On the other part, CSP+T complements the dynamic description of the target system by introducing timed events, which are used to specify timing constraints on events and actions which occur during the execution of processes in real-time systems. Following the work [6]-[8] already done to translate state diagrams into CSP process terms, we can establish a new set of mapping rules between UML-RT entities and CSP+T terms and operators in order to allow the specification of complex temporal dependences between real-time processes. System structural aspects are specified by constructing class diagrams [9], which describe the system composition and associations between its objects. Thereby, we can obtain a specification of all aspects regarding functionality, behaviour and some key temporal properties of any real- time system under development. As to show the applicability of the method, we have used it to carry out the software development of a basic component of a manufacturing industry paradigmatic case: the “Production Cell”. The rest of this paper is structured as follows: section 2 provides an overview on UML-RT and the UML diagrams used in our approach, section 3 explains the system specification method that we propose here. In section 4, using the example of the Production Cell, we present a complete system specification of one of its robot arm controllers. The article ends up with some conclusions and references. II. UML FOR REAL-TIME SYSTEMS UML-RT extends the basic UML [9] analysis entities with constructs to facilitate the design of complex embedded real-time software systems [10]. The origin of the UML-RT modeling notation is the real-time specific modeling language ROOM [11], which has been modified to follow the UML standardized framework. The language focuses primarily on the specification of the architecture of software systems, i.e., their major components, the externally visible properties of these, and the communication between them. The importance of the software architecture definition in the development cycle is argued by considering that decisions made during the architectural design will have a very important impact on the later system design, being also this phase which can profit the most from a good modeling language. Combining the Description Features of UML- RT and CSP+T Specifications Applied to a Complete Design of Real-Time Systems Kawtar Benghazi Akhlaki, and Manuel I. Capel-Tuñón U World Academy of Science, Engineering and Technology 7 2005 193