A shared concern of many shallow parsers is the application to large text corpora. Frequently partial analyses are allowed if the parser is not potent enough to resolve all problems. It has been applied to millions of words. These sentences are partly skeleton parsed , i.e., clear constituents are bracketed but difficult problems may be left open. It provides approximate parses if all requisite information is not available.
Rules are available for ranking alternative parses.
For many sentences, PEG provides thorough syntactic analyses. Constraint Grammar syntax stamps each word in the input sentence with a surface syntactic tag. One central idea is to have most of the morphological disambiguation done by the syntactic constraints proper. There is a need for automatic or semiautomatic discovery procedures that infer rules and rule sets for morphological analyzers from large corpora. Such procedures would make it possible to partially automate the construction of morphological analyzers .