Extended Dependency Unification Grammar

A quick way of gaining a first impression of a formalism is looking at concrete examples. The sentence Arthur attends the Prague meeting. is turned into the following representation by the PLAIN parser: (UTTERANCE: assertion': clause type[main] (< PROPOSITION: attend: verb form[finite] tense[present] person[3rd] number[singular] (< SUBJECT: Arthur: noun person[3rd] number[singular]) (> DIROBJECT: meeting: noun (< DETERMINATION: definit': determiner sequence[1]) (< ATTRIBUTE: Prague: noun sequence[2])))); Fig. 1: Representation of a sentence Fig. 1 is an instance of the so-called Dependency Representation Language (DRL). DRL is used for all purposes in the PLAIN system, e.g. for representing parsing output, for storing information in a knowledge base, for writing grammars and lexica, for writing semantic rules, and as the source for generating natural language output. DRL is, as it were, the programming language of the linguist in order to make the system analyse and process a particular natural language. The expressions of DRL are lists (in the technical sence of list processing) consisting of terms; each sublist is included in parentheses, including sublists consisting of just one term. A list corresponds to a graph, in particular, to a tree. The structure of the tree in fig. 1 is elucidated by the indenting of the terms. Each term carries three kinds of labels: a role, a lexeme, and a complex category. The latter consists of a main category and a set of grammatical attributes followed by their values in square brackets. The symbols "<" and ">" indicate that the subsequent subtree corresponds to a segment in the input which is left or right to the segment corresponding to the term