Introduction

The Abstract State Machine approach has been and is successfully used to model a large number of case studies including industry-relevant ones. The simplicity of the basic data and execution model of ASMs makes them perfectly suitable as the basis for a language that on the one hand can be used as specification language and on the other hand as a high-level programming language. In this paper, the XASM ( Extensible ASM)language is presented which aims at providing support for using ASMs as a programming language for producing efficient and reusable programs. There exists a number of other ASM implementations which all implement most of the ASM constructs as defined in the Lipari-Guide [15]. While the realization of the ASM constructs can be seen as the core functionality which must be present in each ASM support system, the difference of an ASM system compared to all others can be characterized by

• its efficiency,
• the functionality of its support environment,
• its rule abstraction concept, and
• its interoperability with other languages and systems.

For example, all ASM implementations - including XASM- define some macro structures on top of the core ASM language in order to provide some kind of rule abstraction concept. These additional features are indispensable for managing large formalizations. In the ASM-Workbench [12], for instance, the a special ``Rule'' construct is introduced being used to assemble ASM specifications from smaller pieces.

Concerning these features, XASM combines the advantages of using a formally defined method with the features of a full-scale, component-based programming language and its support environment.

The paper is organized as follows: In Section 2 an overview of XASM is given. Section 3 introduces the component-based module concept of XASM, in Section 4 the external language interface of XASM is described. In Section 6 the possibility to specify the syntax of input languages using context-free grammar definitions is presented, which is followed by the description of non-standard language constructs defined in XASM in Section 5. Section 7 sketches the support environment of XASM; Section 8 contains concluding remarks and points out future work.