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The parser is implemented using a reduction of the formulation of TDG outlined in (Duchier and Debusmann 2001) into a constraint problem stated in terms of finite sets. The reduction is more thoroughly described in (Duchier 99) (Duchier 00) (Duchier 01). Parsing amounts to searching for solutions of the CSP which describes the valid ID/LP analyses for a given input. Thereby, we apply alternating propagation and distribution steps. With the help of the selection constraint developed by Denys Duchier, we achieve very strong propagation. In fact, in many cases no search at all is necessary, in spite of substantial lexical and structural ambiguity.
It is possible to switch the parser into generate mode. In generate mode, the parser regards the list of words comprising the string to parse not as a list but a bag of words. Hence, the parser finds all ID/LP analyses which are licensed for this bag of words. Generate mode can be used to debug a grammar: it can help finding undesired ID/LP analyses. It is also employed by the graphical user interface (see chapter 5) to generate the set of linearizations licensed for a bag of words.
The TDG parser allows to individually toggle each of the ID, LP and ID/LP principles on and off which also facilitates grammar debugging.
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