Abstract. This paper describes the Java Language Extender framework, a tool that allows one to create new domain-adapted languages by importing domain-specific language extensions into an extensible implementation of Java 1.4. Language extensions may define the syntax, semantic analysis, and optimizations of new language constructs. Java and the language extensions are specified as higher-order attribute grammars. We describe several language extensions and their implementation in the framework. For example, one embeds the SQL database query language into Java and statically checks for syntax and type errors in SQL queries. The tool supports the modular specification of composable language extensions so that programmers can import into Java the unique set of extensions that they desire. When extensions follow certain restrictions, they can be composed without requiring any implementation-level knowledge of the language extensions. The tools automatically compose the selected extensions and the Java host language specification. 1

Attribute grammar specification languages, like many domain specific languages, offer significant advantages to their users, such as high-level declarative constructs and domain-specific analyses. Despite these advantages, attribute grammars are often not adopted to the degree that their proponents envision. One practical obstacle to their adoption is a perceived lack of the both domain-specific and general purpose language features needed to address all of the different aspects of a problem. Here we describe Silver, an extensible attribute grammar specification language, and show how it can be extended with general purpose features such as pattern matching and domain specific features such as collection attributes and constructs for supporting data-flow analysis of imperative programs. Silver is implemented in itself by a Silver attribute grammar and utilizes forwarding to implement the extensions in a cost-effective manner. The result is an attribute grammar specification language with a rich set of language features.

Abstract. ADDS (Approach to Document-based Development of Software) is an approach to the development of applications based on a document-oriented paradigm. According to this paradigm, applications are described by means of documents that are marked up using descriptive domain-specific markup languages. Afterwards, applications are produced processing these marked up documents. Formulation of domain-specific markup languages in ADDS is a dynamic and eminently pragmatic activity since these languages evolve in accordance with the authoring needs of the main actors that participate in the development process (i.e. domain experts and developers). OADDS (Operationalization in ADDS) is a processing model that promotes the construction of modular language processors and their incremental evolution. Thus, OADDS is specifically designed to cope with the evolutionary nature of the domain-specific markup languages encouraged by ADDS. ADDS and OADDS have successfully been applied to the development of applications in knowledge-intensive domains (i.e. transport networks and educational hypermedias). This paper also describes the advantages (incremental development and maintenance improvement) that this approach supposes for the development of knowledge-based systems. 1

Abstract. This paper presents ADDS, a systematic approach to sofware development using Domain-Specific Languages (DSLs) and markup technologies. XML is used as a common descriptive framework for DSLs formulation, obtaining Domain Specific Markup Languages (DSMLs). According to ADDS, the construction of applications in a domain starts with the provision of suitable DSMLs. Then, the applications in such a domain are described by means of sets of structured documents conforming these DSMLs. Finally, the application is produced by processing this documentation according to an operationalization model called OADDS. Hence ADDS provides a systematic approach to software development based on the processing of XMLdocumentation that can be used in a great variety of domains. 1

Domain specific languages (DSLs) are increasingly used today. Coping with complex language definitions, evolving them in a structured way, and ensuring their error freeness are the main challenges of DSL design and implementation. The use of modular language definitions and composition operators are therefore inevitable in the independent development of language components. In this article, we discuss these arising issues by describing a framework for the compositional development of textual DSLs and their supporting tools. We use a redundance-free definition of a readable concrete syntax and a comprehensible abstract syntax as both representations significantly overlap in their structure. For enhancing the usability of the abstract syntax, we added concepts like associations and inheritance to a grammarbased definition in order to build up arbitrary graphs (as known from metamodeling). Two modularity concepts, grammar inheritance and embedding, are discussed. They permit compositional language definition and thus simplify the extension of languages based on already existing ones. We demonstrate that compositional engineering of new languages is a useful concept when project-individual DSLs with appropriate tool support are defined.

A definition of the semantics of attribute grammars is given, using the lambda calculus. We show how this semantics allows us to prove results about attribute grammars in a calculational style. In particular, we give a new proof of Chirica and Martin's result [6], that the attribute values can be computed by a structural recursion over the tree. We also derive a new definedness test, which encompasses the traditional closure and circularity tests. The test is derived by abstract interpretation.

Abstract. Name analysis for Java is challenging with its complex visibility rules involving nested scopes, inheritance, qualified access, and syntactic ambiguities. We show how Java name analysis including ambiguities related to names of variables, fields, and packages, can be implemented in a declarative and modular manner using the JastAdd compiler construction system. Declarative attributes and context-dependent rewrites enable the implementation to be modularized in the same way as the informal Java language specification. The individual rules in the specification transfer directly to equations in the implementation. Rewrites are used to define new concepts in terms of existing concepts in an iterative manner in the same way as the informal language specification. This enables equations to use both context-free and context-dependent concepts and leads to improved separation of concerns. A full Java 1.4 compiler has been implemented to validate the technique. 1

Abstract. In model-based development, a formal description of the software (the model) is the central artifact that drives other development activities. The availability of a modeling language well-suited for the system under development and appropriate tool support are of utmost importance to practitioners. Considering the diverse needs of different application domains, flexibility in the choice of modeling languages and tools may advance the industrial acceptance of formal methods. We describe a flexible modeling language framework by which language and tool developers may better meet the special needs of various users groups without incurring prohibitive costs. The framework is based on a modular and extensible implementation of languages features using attribute grammars and forwarding. We show a prototype implementation of such a framework by extending the host language Mini-Lustre, an example synchronous data-flow language, with a collection of features such as state transitions, condition tables, and events. We also show how new languages can be created in this framework by feature composition. 1

We show how new syntactic forms and static analysis can be added to a programming language to support abstractions provided by libraries. Libraries have the important characteristic that programmers can use multiple libraries in a single program. Thus, any attempt to extend a language’s syntax and analysis should be done in a composable manner so that similar extensions that support other libraries can be used by the programmer in the same program. To accomplish this we have developed an extensible attribute grammar specification of Java 1.4 written in the attribute grammar specification language Silver. Library writers can specify, as an attribute grammar, new syntax and analysis that extends the language and supports their library. The Silver tools automatically compose the grammars defining the language and the programmer-selected language extensions (for their chosen libraries) into a specification for a new custom language that has language-level support for the libraries. We demonstrate how syntax and analysis are added to a language by extending Java with syntax from the query language SQL and static analysis of these constructs so that syntax and type errors in SQL queries can be detected at compile-time. 1.

In this paper we present a macro system for the Fortress programming language. Fortress is a new programming language designed for scientific and high-performance computing. Features include: implicit parallelism, transactions, and concrete syntax that emulates mathematical notation. Fortress is intended to grow over time to accommodate the changing needs of its users. Our goal is to design and implement a macro system that allows for such growth. The main challenges are (1) to support extensions to a core syntax rich enough to emulate mathematical notation, (2) to support combinations of extensions from separately compiled macros, and (3) to allow new syntax that is indistinguishable from core language constructs. To emulate mathematical notation, Fortress syntax is specified as a parsing expression grammar (PEG), supporting unlimited lookahead. Macro definitions must be checked for well-formedness before they are expanded and macro uses must be well encapsulated (hygienic, composable, respecting referential transparency). Use sites must be parsed along with the rest of the program and expanded directly into abstract syntax trees. Syntax errors at use sites of a macro must refer to the unexpanded program at use sites, never to definition sites. Moreover, to allow for many common and important uses of macros, mutually recursive definitions should be supported. Our design meets these challenges. The result is a flexible system that allows us not only to support new language extensions, but also to move many constructs of the core language into libraries. New grammar productions are tightly integrated with the Fortress parser, and use sites expand into core abstract syntax trees. Our implementation is integrated into the open-source Fortress reference interpreter.To our knowledge, ours is the first implementation of a modular hygienic macro system based on parsing expression grammars.