پديد آورندگان :
صادق زاده، محمدباقر دانشگاه صنعتي اميركبير، تهران , رزازي، محمدرضا دانشگاه صنعتي اميركبير، تهران , قيومي، مسعود پژوهشگاه علوم انساني و مطالعات فرهنگي، تهران
كليدواژه :
دستور مستقل از متن آماري , تجزيه‌گر , تركيبات عطفي , نشانه‌گذاري قواعد , برچسب اجزاي واژگاني كلام
چكيده فارسي :
عدم دقّت در طراحي دستورهاي مستقل از متن و استفاده از ساختارهاي نامناسب مانند فرم نرمال چامسكي به خودي خود مي‌تواند عملكرد تجزيه‌‍گرهاي آماري مستقل از متن را تضعيف كند. در اين پژوهش ساختار تركيبات عطفي درخت‌بانك فارسي را مورد بررسي قرار داديم. نتايج حاصل از اين پژوهش نشان مي‌دهد كه با اضافه‌كردن وابستگي‌هاي ساختاري به دستورهاي مستقل از متن و اصلاح قواعد اوليه، مي‌‌توان از تركيبات عطفي رفع ابهام كرد و صحت عملكرد تجزيه‌گر دستور مستقل از متن آماري را افزايش داد. فرض استقلال ضعيف، يكي از مشكلات مربوط به دستورهاي مستقل از متن است كه سعي شده است تا با تزريق وابستگي‌هاي ساختاري از طريق نشانه‌گذاري گره‌هاي والد و فرزند مرتفع شود. تأثير ريزدانگي و درشتدانگي برچسب‌هاي اجزاي واژگاني كلام و همين‌طور ادغام ناپايانه‌ها بر تجزيه‌گر دستور مستقل از متن آماري فارسي از جمله مواردِ مورد بررسي قرار گرفته‌شده در اين پژوهش است.
چكيده لاتين :
In linguistics, a tree bank is a parsed text corpus that annotates syntactic or semantic sentence structure. The exploitation of tree bank data has been important ever since the first large-scale tree bank, The Penn Treebank, was published. However, although originating in computational linguistics, the value of tree bank is becoming more widely appreciated in linguistics research as a whole. For example, annotated tree bank data has been crucial in syntactic research to test linguistic theories of sentence structure against large quantities of naturally occurring examples.
The natural language parser consists of two basic parts, POS tagger and the syntax parser. A Part-Of-Speech Tagger (POS Tagger) is a piece of software that reads text in some languages and assigns parts of speech to each word (and other token), such as noun, verb, adjective, etc., although generally computational applications use more fine-grained POS tags like 'noun-plural'. A natural language parser is a program that works out the grammatical structure of sentences, for instance, which groups of words go together (as "phrases") and which words are the subject or object of a verb.
Probabilistic parsers use knowledge of language gained from hand-parsed sentences to try to produce the most likely analysis of new sentences. These statistical parsers still make some mistakes, but commonly work rather well. Inaccurate design of context-free grammars and using bad structures such as Chomsky normal form can reduce accuracy of probabilistic context-free grammar parser.
Weak independence assumption is one of the problems related to CFG. We have tried to improve this problem with parent and child annotation, which copies the label of a parent node onto the labels of its children, and it can improve the performance of a PCFG. In grammar, a conjunction (conj) is a part of speech that connects words, phrases, or clauses that are called the conjuncts of the conjunctions. In this study, we examined the conjunction phrases in the Persian tree bank. The results of this study show that adding structural dependencies to grammars and modifying the basic rules can remove conjunction ambiguity and increase accuracy of probabilistic context-free grammar parser.
When a part-of-speech (PoS) tagger assigns word class labels to tokens, it has to select from a set of possible labels whose size usually ranges from fifty to several hundred labels depending on the language. In this study, we have investigated the effect of fine and coarse grain POS tags and merging non-terminals on Persian PCFG parser.
