There is a real need for clear and sound design specifications of distributed systems at the architectural level. This is the level of the design which deals with the high-level organisation of computational elements and the interactions between those elements. The paper presents the Darwin notation for specifying this high-level organisation. Darwin is in essence a declarative binding language which can be used to define hierarchic compositions of interconnected components. Distribution is dealt with orthogonally to system structuring. The language supports the specification of both static structures and dynamic structures which may evolve during execution. The central abstractions managed by Darwin are components and services. Services are the means by which components interact. In addition to its use in specifying the architecture of a distributed system, Darwin has an operational semantics for the elaboration of specifications such that they may be used at runtime to di...

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Proceedings of the IEEE January 2003 The paper describes a model-integrated approach for embedded software development that is based on domain-specific, multiple view models used in all phases of the development process. Models explicitly represent the embedded software and the environment it operates in, and capture the requirements and the design of the application, simultaneously. Models are descriptive, in the sense that they allow the formal analysis, verification and validation of the embedded system at design time. Models are also generative, in the sense that they carry enough information for automatically generating embedded systems using the techniques of program generators. Because of the widely varying nature of embedded systems, a single modeling language may not be suitable for all domains, thus modeling languages are often domain-specific. To decrease the cost of defining and integrating domain-specific modeling languages and corresponding analysis and synthesis tools, the model-integrated approach is applied in a metamodeling architecture, where formal models of domain-specific modeling languages – called metamodels – play a key role in customizing and connecting components of tool chains. The paper will discuss the principles and techniques of model-integrated embedded software development in detail, as well as the capabilities of the tools supporting the process. Examples in terms of real systems will be given that illustrate how the model-integrated approach addresses the physical nature, the assurance issues, and the dynamic structure of embedded software.

Darwin is a configuration language for distributed and parallel programs, providing a hierarchical structure of components with dynamic binding. In order to specify precisely the behaviour of Darwin programs, we sketch a translation of the features of the language into the ß-calculus, a formalism for modelling concurrent processes. The match between underlying models for Darwin and ß-calculus is good. Examples done in the calculus are clean abstractions of the same solutions in other concurrent languages. 1 Introduction Without a formal specification a language is defined by its compiler and even with the best intentions several compilers for a language will lead to several variants. For any concurrent language designed to be implemented on very different architectures and the importance of a formal language specification becomes paramount. A good specification language is one that enables a clear simple specification to be written. This is most likely if the underlying model that th...

Abstract. Embedded systems represent fundamentally new challenges for software design, which render conventional approaches to software composition ineffective. Starting with the unique challenges of building embedded systems, this paper discusses key issues of model-based technology for embedded systems. The discussion uses Model-Integrated Computing (MIC) as an example for model-based software development. In MIC, domainspecific, multiple view models are used in all phases of the development process. Models explicitly represent the embedded software and the environment it operates in, and capture the requirements of the application, simultaneously. Models are descriptive, in the sense that they allow the formal analysis, verification and validation of the embedded system at design time. Models are also generative, in the sense that they carry enough information for automatically generating embedded systems from them using the techniques of program generators. 1

: This paper shows how Z can be used as a substrate for an architectural style description language. The language provides a collection of abstract software types that support the description of execution and interface semantics, logical views, and relationships between logical views. The software types correspond to application-invariant Z schemas, which provide a type-theoretic basis for the language that allows it to be used for describing, analyzing, and comparing various architectural styles and logical views. 1.. Introduction The field of software architectures deals with the design, construction, maintenance, and structure of large software systems. The study of these systems raises problems analogous to those which motivated the development of data structures, with program modules playing the role of data types. First, identifying common architectural patterns for software systems is analogous to identifying basic data structures such as lists, stacks, and trees. The importanc...

This paper is our attempt to translate the natural language definition of UML's module concept into twelve predicate logic formulas that give precise answers to points (1) and (2) above. Furthermore, we will suggest five additional formulas that address point (3) above. Within all these formulas we will use the following (all-quantified) variables:

The term software architectural style has recently been introduced to refer to the conventions that are used to interpret a description of a software architecture. The representation and analysis of useful architectural styles is an important problem. This paper gives an overview of a methodology developed by the authors for describing the syntax and semantics of software architectural styles with an application to the US Naval Research Laboratory's Processing Graph Method (PGM). This coarse-grain dataflow architectural style has been used for more than ten years to develop signal processing applications in government and industry. 1. Introduction Since the late 1970s, software systems have been designed as collections of modules that interact with their environments through well-defined interfaces [DK]. This perspective gave rise to a number of module interconnection languages (MILs) that could be used to describe the configuration of the modules and interfaces of a software system [...

In memory of my mother, Priscilla C. Davis iii ACKNOWLEDGEMENTS An undertaking such as this cannot be completed alone, and I would like to acknowledge the many persons who helped me succeed in this task. First and foremost, I would like to thank my family. My father and my sister provided must needed support, understanding, and the occasional kick-in-the-pants I needed to survive this journey. Without them, I could not have started, let alone finished, graduate studies. Special thanks to Melissa for all of the support and motivation she gave. She provided my personal support group that got me through the tough times. Her unwavering support is immensely appreciated. Secondly, I would like to thank each and every member of my Ph.D. committee for their comments, insight, and direction. My advisor, Dr. Janos Sztipanovits, merits special thanks for the many years of leadership. His insight, determination, dedication, and desire to explore new ideas has been an inspiration. Dr. Sztipanovits would always allow me the

: UML is the first OO modeling language with a useful modularization and information hiding concept. It supports nesting, import, and refinement of so-called packages. This paper translates UML's informal package definition into predicate logic formulas and solves some open problems concerning the visibility of exported and imported modeling elements. Furthermore, the formulas will be transformed into a specification based on PROgrammed Graph REwriting Systems. We will very briefly sketch how a graphical UML editor can be generated from this PROGRES specification. 1 Introduction After about 20 years of research and development, object-oriented (OO) modeling methods and notations have reached a certain degree of maturity and acceptance. They are no longer the occult science of a small number of OO gurus, but the widely accepted approach for analysis (OOA) and design (OOD) of software (hardware) systems. Popular OO methods --- like Booch (1994), OMT (Rumbaugh et al. (1991)), or OOSE (...