ABSTRACT
This chapter examines Alternative Parsing Strategies. Before examining some alternative strategies, it will prove useful to consider another way of producing a top-down, depth-first, and left-to-right strategy for definite clause grammars (DCGs). If Prolog were only suitable for expressing the one strategy, this would severely restrict its usefulness as a tool for Natural Language Processing (NLP) research. However, one of the strengths of Prolog is the ease with which it is possible to devise other control strategies. The rules of the grammar were initially translated into Prolog clauses which were then directly executed. The approach adopted here is for the DCG rules to form a database for another program to access and manipulate during its execution as needs be. Programs which manipulate other programs in this way are called interpreters. It is because the same DCG rules can be used by different interpreters that different parsing strategies are possible.
