Statecharts, popular for modelling system behavior in the structural analysis paradigm, are part of a fully executable language set for modelling object-oriented systems. The languages form the core of the emerging Unified Modelling Language.

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ion Abstract: This paper seeks to establish within a formal framework how Coloured Petri Nets can be enhanced to produce Object Petri Nets. It does so by defining a number of intermediate Petri Net formalisms and identifying the features introduced at each step of the development. Object Petri Nets support a complete integration of object-oriented concepts into Petri Nets, including inheritance and the associated polymorphism and dynamic binding. In particular, Object Petri Nets have a single class hierarchy which includes both token types and subnet types. Interaction between subnets can be either synchronous or asynchronous depending on whether the subnet is defined as a super place or a super transition. The single class hierarchy readily supports multiple levels of activity in the net and the generation and removal of tokens has been defined so that all subcomponents are simultaneously generated or removed, thus simplifying memory management. Despite this descriptive power, Object...

The POEMS project is creating an environment for end-to-end performance modeling of complex parallel and distributed systems, spanning the domains of application software, runtime and operating system software, and hardware architecture. Towards this end, the POEMS framework supports composition of component models from these different domains into an end-to-end system model. This composition can be specified using a generalized graph model of a parallel system, together with interface specifications that carry information about component behaviors and evaluation methods. The POEMS Specification Language compiler, under development, will generate an end-to-end system model automatically from such a specification. The components of the target system may be modeled using different modeling paradigms (analysis, simulation, or direct measurement) and may be modeled at various levels of detail. As a result, evaluation of a POEMS end-to-end system model may require a variety of eval...

Schema evolution is a problem that is faced by long-lived data. When a schema changes, existing persistent data can become inaccessible unless the database system provides mechanisms to access data created with previous versions of the schema. Most existing systems that support schema evolution focus on changes local to individual types within the schema, thereby limiting the changes that the database maintainer can perform. We have developed a model of type changes incorporating changes local to individual types as well as compound changes involving multiple types. The model describes both type changes and their impact on data by defining derivation rules to initialize new data based on the existing data. The derivation rules can describe local and nonlocal changes to types to capture the intent of a large class of type change operations. We have built a system called Tess (Type Evolution Software System) that uses this model to recognize type changes by comparing schemas and then produces a transformer that can update data in a database to correspond to a newer version of the schema.

TROLL light is a language for conceptual modeling of information systems. It is designed to describe the Universe of Discourse (UoD) as a system of concurrently existing and interacting objects. TROLL light objects have observable properties modeled by attributes, and the behavior of objects is described by events. Possible object observations may be restricted by constraints, whereas event occurrences may be restricted to specified life cycles. TROLL light objects are organized in an object hierarchy established by subobject relationships. Communication among objects is supported by event calling. Apart from introducing the various possibilities for the syntactical description of objects, we aim to describe how the state of an object community may be changed by event occurrences. 1 Introduction In recent years formal specification techniques have been receiving more and more attention (see for example [CHJ86, TM87, Win90]). Formal specifications are used for supporting the program an...

The POEMS project is creating an environment for endto -end performance modeling of complex parallel and distributed systems, spanning the domains of application software, runtime and operating system software, and hardware architecture. To enable end-to-end modeling of large-scale applications and systems, the POEMS framework is designed to compose models of system components from these different domains, to integrate multiple modeling paradigms (analytical modeling, simulation, and actual system execution), and to allow different components to be modeled at multiple levels of detail. The key components of the POEMS framework include a generalized task graph model for describing parallel computations, automatic generation of the task graph by a parallelizing compiler, a specification language for mapping the computation on models for operating system and hardware components, a library of analytical and simulation models for components from the different domains, and a knowledge base d...

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Abstract. This paper presents the OOA design step in a methodology which integrates automata-based model checking into a commercially supported OO software development process. We define and illustrate a set of design rules for OOA models with executable semantics, which lead to automata models with tractable state spaces. The design rules yield OOA models with functionally structured designs similar to those of hardware systems. These structures support modelchecking through techniques known to be feasible for hardware. The formal OOA methodology, including the design rules, was applied to the design of NASA robot control software. Serious logical design errors that had eluded prior testing, were discovered in the course of model-checking. 1