However, traditional formal grammars have generally not covered any one language comprehensively, and have drawn sharp boundaries between well-formedness and ill-formedness, when in fact people's (including linguists') grammaticality judgments for many sentences are uncertain or equivocal. Moreover, when we seek to process sentences “in the wild”, we would like to accommodate regional, genre-specific, and register-dependent variations in language, dialects, and erroneous and sloppy language (e.g., misspellings, unpunctuated run-on sentences, hesitations and repairs in speech, faulty constituent orderings produced by non-native speakers, and fossilized errors by native speakers, such as “for you and I”—possibly a product of schoolteachers inveighing against “you and me” in subject position). Consequently linguists' idealized grammars need to be made variation-tolerant in most practical applications. The way this need has typically been met is by admitting a far greater number of phrase structure rules than linguistic parsimony would sanction—say, 10,000 or more rules instead of a few hundred. These rules are not directly supplied by linguists (computational or otherwise), but rather can be “read off” corpora of written or spoken language that have been decorated by trained annotators (such as linguistics graduate students) with their basic phrasal tree structure. Unsupervised grammar acquisition (often starting with POS-tagged training corpora) is another avenue  (see section 9), but results are apt to be less satisfactory. In conjunction with statistical training and parsing techniques, this loosening of grammar leads to a rather different conception of what comprises a grammatically flawed sentence: It is not necessarily one rejected by the grammar, but one whose analysis requires some rarely used rules.