Extended abstract

Parsing schemata [4] provide a formal, simple and uniform way to describe, analyze and compare different parsing algorithms. The notion of a parsing schema comes from considering parsing as a deduction process which generates intermediate results called items. An initial set of items is directly obtained from the input sentence, and the parsing process consists of the application of inference rules (called deductive steps) which produce new items from existing ones. Each item contains a piece of information about the sentence’s structure, and a successful parsing process will produce at least one final item containing a full parse tree for the sentence or guaranteeing its existence. Their abstraction of low-level details makes parsing schemata very useful, allowing us to define parsers in a simple and straightforward way. Comparing parsers, or considering aspects such as their correction and completeness or their computational complexity, also becomes easier if we think in terms of schemata. However, when we want to actually use a parser by running it on a computer, we need to implement it in a programming language, so we have to abando