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Machine Compiler while loops into a compiler We formally de ned similar transformations and implemented them in Prolog Applying our system to the above mentioned toy language yields similar results The goal of our work is to apply the method to speci cations of realistic programming languages and thus detecting missing links insu ciencies and possible optimizations of the transformations We decided to use action notation as such a programming language because it o ers a rich set of primitives underlying both imperative and functional programming languages Two Level Big Step Semantics BIG First we give the syntax of BIG a language designed to write natural semantics speci cations The language combines the structural approach of natural semantics with the idea to split general and implementation details by the use of a separately given interpretation for function symbols T f T j c T j x x variable symbol T c T c constructor symbol C T f function name C T p predicate name E T E T S C E E S C E E Q p T j not p T J S j Q R J S Judgements are transitions of the form C E E or side conditions of the form p T or not p T We will use the term left hand side to refer to C E in a transition and the term right hand side to refer to E In a rule of the form J S the judgements above the line are called preconditions and the judgement below the line is called the conclusion We will denote the variables in a term t by V t Furthermore we adopt the notation for list constructors from Prolog Speci cations in BIG have to be determinate i e whenever two rules have conclusions which unify with a goal at most one of the rules can be successfully applied The restriction to determinate rule sets is important because determinate rule sets can be converted into deterministic ones i e at most one rule will have a conclusion which uni es with a goal Deterministic rules can be converted into term rewriting rules and nally these rewrite rules can be pass separated into rewrite rules for a compiler and an abstract machine In the next section the transformations are discussed in more detail Generating Compilers and Abstract Machines from BIG Spec i cations An overview of the system is given in Figure Since the system transforms speci cations by successively applying transformations we will present the transformations in the order of their application Actually the transformations have been devised in reversed order Starting from the pass separation transformation we tried to remove restrictions on the input speci cations by transforming a more general class of speci cations into the class of input speci cations This process nally lead to determinate BIG speci cations Note that after each transformation we have an executable speci cation again Transformation of Side Conditions This transformation converts side conditions into judgements Let c e e be the conclusion of a rule Side conditions of the form p t tn are converted into a x xk y ym true Automatic Generation of a Compiler and Abstract Machine for Action Notation Preliminary Results Stephan Diehl FB Informatik Universit at des Saarlandes Postfach Saarbr ucken GERMANY diehl cs uni sb de