Attribute grammars were introduced by D. Knuth [1] and since then have proved to be useful in specifying the semantics of programming languages and in the automatic construction of compilers and interpreters. While implementation of programming languages is the original and most-widely recognized area of attribute grammars, they are also used in many other areas such as [2]: natural language interfaces, graphical user interfaces, visual programming, pattern recognition, hardware design, communication protocols, software engineering, static analysis of programs, databases, etc. However, only a few commercial compilers have been developed using attribute grammars as a design and implementation tool. It has been argued that attribute grammars are unsuitable for the production of high-speed compilers for general-purpose programming languages, since they are just a model of compilation and, thus, too primitive for real engineering discipline, and that they do not directly support the generation and optimization of machine code. The first problem is concerned with the pragmatic aspects of ordinary attribute grammars. Ordinary attribute grammars have deficiencies which become apparent in specifications for real programming languages. Such specifications are large, unstructured, and hard to understand, modify and maintain. Yet worse still, small modifications of some parts in the specification have widespread effects on the other specification parts. There has been a lot of research work on augmenting ordinary attribute grammars with extensions in order to overcome the deficiencies of attribute grammars, such as lack of modularity, extensibility and reusability. Several concepts, such as remote attribute access, object-orientation, templates, rule models, symbol computations, high order features etc., have been implemented in various attribute grammar specification languages. This problem is still insufficiently solved, despite all these different approaches. The aspect-oriented attribute grammar, introduced in this paper, is proposed to better solve this problem. In aspect-oriented attribute grammar, concepts from aspect-oriented programming [3] have been integrated with attribute grammars. Aspect-oriented programming is a recently proven approach for describing crosscutting concerns in a modular manner. The second problem of attribute grammars, the lack of proper support for code generation and optimization, has also been insufficiently solved as yet and is out of the scope of this paper. An immediate conclusion might be, however, that attribute grammars are more appropriate in the design and implementation of Domain-Specific Languages (DSLs) [4] rather than for development of conventional optimizing compilers. Domain-specific languages, such as database query languages, robot-control languages, hardware design languages, and mark-up languages are usually developed with an emphasis on high-level application abstractions rather than on optimal performance. On the other hand, there is a strong case for formally specifying the syntax and semantics of DSLs [4]. The proposed aspect-oriented attribute grammar is a feasible formalism from which a DSL compiler, as well as related tools, (e.g., debuggers) [5] can be automatically generated.
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