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The stationary hypothesis is relaxed in MEMM, and the nonstationary MEMM (NS-MEMM) is proposed. Several related issues are discussed in detail, including the representation of positional information, NS-MEMM implementation, smoothing techniques, and the space complexity issue. Furthermore, the asymmetric NS-MEMM presents a more flexible way to exploit positional information. In the experiments, NS-MEMM is evaluated on both the Chinese and the English pos-tagging tasks. According to the experimental results, NS-MEMM yields effective improvements over MEMM by exploiting positional information. The smoothing techniques in this article effectively solve the NS-MEMM data-sparseness problem; the asymmetric NS-MEMM is also an improvement by exploiting positional information in a more flexible way.<\/jats:p>","DOI":"10.1145\/1282080.1282082","type":"journal-article","created":{"date-parts":[[2007,10,14]],"date-time":"2007-10-14T12:41:11Z","timestamp":1192365671000},"page":"7","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":4,"title":["The study of a nonstationary maximum entropy Markov model and its application on the pos-tagging task"],"prefix":"10.1145","volume":"6","author":[{"given":"Jinghui","family":"Xiao","sequence":"first","affiliation":[{"name":"Harbin Institute of Technology, Harbin, China, P.C."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaolong","family":"Wang","sequence":"additional","affiliation":[{"name":"Harbin Institute of Technology, Harbin, China, P.C."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bingquan","family":"Liu","sequence":"additional","affiliation":[{"name":"Harbin Institute of Technology, Harbin, China, P.C."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"320","published-online":{"date-parts":[[2007,9]]},"reference":[{"doi-asserted-by":"publisher","key":"e_1_2_1_1_1","DOI":"10.1109\/34.771314"},{"doi-asserted-by":"publisher","key":"e_1_2_1_2_1","DOI":"10.5555\/176313.176316"},{"doi-asserted-by":"publisher","key":"e_1_2_1_3_1","DOI":"10.1109\/89.817452"},{"doi-asserted-by":"publisher","key":"e_1_2_1_4_1","DOI":"10.3115\/1219840.1219903"},{"doi-asserted-by":"crossref","unstructured":"Cover T. 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