Abstract. Object-oriented design patterns have been one of the most important and successful ideas in software design over the last ten years, and have been well adopted both in industry and academia. A number of open research problems remain regarding patterns, however, including the differences between patterns, variant forms of common patterns, the naming of patterns, the organisation of collections of patterns, and the relationships between patterns. We provide a semiotic account of design patterns, treating a pattern as a sign comprised of the programmers ’ intent and its realisation in the program. Considering patterns as signs can address many of these common questions regarding design patterns, to assist both programmers using patterns and authors writing them. 1

Design patterns are of major interest to increase software quality and abstraction level. However, design patterns are difficult to choose, to apply, and to recover. We propose a set of tools to use design patterns in a round-trip fashion. We define a meta-model to describe design patterns. This meta-model is specifically oriented towards design patterns instantiation and detection. We develop a source-to-source transformation engine to modify the source code to comply with design patterns descriptions. Meanwhile, we use an explanationbased constraint solver to detect design patterns in source code from their descriptions. With these tools, we hope to offer a mean to apply and to recover design patterns without overhead for the developers. ∗This work is partly funded by Soft-Maint – 4, rue du Château de l ’ Éraudière – 44 324 Nantes –

Abstract—Executable language model driven by data streams is proposed. At the same time, this model is language architecture developed from context-free grammar enriched with communication channels. Four types of formal communication channels and one type of informal communication channel were identified for functional languages, to provide systematic background for human-machine communication. Formal channel positions are determined by a grammar, not by a programmer. Data streams are aproximately as concise as computer machine code but they are semantically equivalent to high-level programs. Using simple example of functional language we present the principle of functional language architecture construction and its driving by data stream. In particular, we show how the program is initially recorded, and how it can be repeatedly generated, either in original or in a modified version. Data streams radically decrease structural complexity of current programs, preserving their semantics, since they are not executed at low-level computer architecture but at high-level language architecture. Index Terms—Executable modeling, language models, language architectures, data driven program generation, domain