Separable Verbs in a Reusable Morphological Dictionary for German

Separable verbs are verbs with prefixes which, depending on the syntactic context, can occur as one word written together or discontinuously. They occur in languages such as German and Dutch and constitute a problem tbr NLP because they are lexemes whose lbrms cannot always be recognized by dictionary lookup on the basis of a text word. Conventional solutions take a mixed lexical and syntactic approach. In this paper, we propose the solution offered by Word Manager, consisting of string-based recognition by means of rules of types also required for periphrastic inflection and clitics. In this way, separable verbs are dealt with as part of the dolnain of reusable lexical resources. We show how this solution compares favourably with conventional approaches. 1. The P r o b l e m In German there exists a large class of verbs which behave like aufhOren ( ' s top ' ) , illustrated in (1). (1) a. Anna glaubt, dass Bernard aufhSrt. ( 'Anna believes that Bernard stops') b. Claudia h6rt jetzt auf. ( 'Claudia stops now PRY') c. Daniel versucht aufzuh6ren. ('Daniel tries to_stop') In subordinate clauses as in ( I a), the particle aufand the inflected part of the verb hOrt are written together, in main clauses such as (lb), the inflected form hOrt is moved by verb-second, leaving the particle stranded. In infinitive clauses with the particle zu ( 'to'), zu separates the two components of the verb and all three elements are written together. In analysis, the problem of separable verbs is to combine the two parts of the verb in contexts such as ( lb) and (lc). Such a combination is necessary because syntactic and semantic properties of aufhiJren are the same, irrespective of whether the two parts are written together or not, but they cannot be deduced from the syntactic and semantic properties of the parts. Therefore, a solution to the problem of separable verbs will treat (lb) as if it read (2a) and (lc) as (2b): (2) a. Claudia auihOrtjctzt. b. Daniel versucht zu aulh6ren. The problem arises in a very similar fashion in Dutch, as the Dutch translations (3) of the sentences in (1) show. The only difference is that the infinitive in (3c) is not written together. (3) a. Anna geloofl dat Bernard ophoudt. b. Claudia houdt nu op. c. Daniel probeert op te houden. On the other hand, the problem of separable verbs in German and Dutch differs flom the corresponding one in English, because English verbs such as look up are multiword units in all contexts. A treatment of these cases which is in lille: with the solution proposed here is described by Tschichold (forthcoming). As suggested by the English translation, separable verbs in German and Dutch are lexemes. Therefore, an important issue in evaluating a mechanism for dealing with them is how it fits in with the reusability of lexical resources. Given the importance of the orthographic componen t in the problem, it is not surprising that it is hardly if ever treated in the linguistic literature.