{"id":"https://openalex.org/W2036850631","doi":"https://doi.org/10.1016/s0022-0000(73)80002-9","title":"The unsolvability of the equality problem for sentential forms of context-free grammars","display_name":"The unsolvability of the equality problem for sentential forms of context-free grammars","publication_year":1973,"publication_date":"1973-10-01","ids":{"openalex":"https://openalex.org/W2036850631","doi":"https://doi.org/10.1016/s0022-0000(73)80002-9","mag":"2036850631"},"language":"en","primary_location":{"id":"doi:10.1016/s0022-0000(73)80002-9","is_oa":false,"landing_page_url":"https://doi.org/10.1016/s0022-0000(73)80002-9","pdf_url":null,"source":{"id":"https://openalex.org/S141020589","display_name":"Journal of Computer and System Sciences","issn_l":"0022-0000","issn":["0022-0000","1090-2724"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310320990","host_organization_name":"Elsevier BV","host_organization_lineage":["https://openalex.org/P4310320990"],"host_organization_lineage_names":["Elsevier BV"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Journal of Computer and System Sciences","raw_type":"journal-article"},"type":"article","indexed_in":["crossref"],"open_access":{"is_oa":false,"oa_status":"closed","oa_url":null,"any_repository_has_fulltext":false},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5020117665","display_name":"Meera Blattner","orcid":null},"institutions":[{"id":"https://openalex.org/I161318765","display_name":"University of California, Los Angeles","ror":"https://ror.org/046rm7j60","country_code":"US","type":"education","lineage":["https://openalex.org/I161318765"]},{"id":"https://openalex.org/I197461853","display_name":"Los Angeles Harbor College","ror":"https://ror.org/028nyzb21","country_code":"US","type":"education","lineage":["https://openalex.org/I197461853"]}],"countries":["US"],"is_corresponding":true,"raw_author_name":"Meera Blattner","raw_affiliation_strings":["Los Angeles Harbor College, Wilmington, California, USA","The University of California at Los Angeles, Los Angeles, California, USA"],"affiliations":[{"raw_affiliation_string":"Los Angeles Harbor College, Wilmington, California, USA","institution_ids":["https://openalex.org/I197461853"]},{"raw_affiliation_string":"The University of California at Los Angeles, Los Angeles, California, USA","institution_ids":["https://openalex.org/I161318765"]}]}],"institutions":[],"countries_distinct_count":1,"institutions_distinct_count":1,"corresponding_author_ids":["https://openalex.org/A5020117665"],"corresponding_institution_ids":["https://openalex.org/I161318765","https://openalex.org/I197461853"],"apc_list":{"value":2520,"currency":"USD","value_usd":2520},"apc_paid":null,"fwci":4.9152,"has_fulltext":false,"cited_by_count":25,"citation_normalized_percentile":{"value":0.95958854,"is_in_top_1_percent":false,"is_in_top_10_percent":true},"cited_by_percentile_year":null,"biblio":{"volume":"7","issue":"5","first_page":"463","last_page":"468"},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T11567","display_name":"semigroups and automata theory","score":0.9994000196456909,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},"topics":[{"id":"https://openalex.org/T11567","display_name":"semigroups and automata theory","score":0.9994000196456909,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T12029","display_name":"DNA and Biological Computing","score":0.9984999895095825,"subfield":{"id":"https://openalex.org/subfields/1312","display_name":"Molecular Biology"},"field":{"id":"https://openalex.org/fields/13","display_name":"Biochemistry, Genetics and Molecular Biology"},"domain":{"id":"https://openalex.org/domains/1","display_name":"Life Sciences"}},{"id":"https://openalex.org/T12002","display_name":"Computability, Logic, AI Algorithms","score":0.9972000122070312,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}}],"keywords":[{"id":"https://openalex.org/keywords/undecidable-problem","display_name":"Undecidable problem","score":0.7451958060264587},{"id":"https://openalex.org/keywords/equivalence","display_name":"Equivalence (formal languages)","score":0.7274892330169678},{"id":"https://openalex.org/keywords/context-free-grammar","display_name":"Context-free grammar","score":0.6545616388320923},{"id":"https://openalex.org/keywords/mathematics","display_name":"Mathematics","score":0.6177360415458679},{"id":"https://openalex.org/keywords/rule-based-machine-translation","display_name":"Rule-based machine translation","score":0.6086971759796143},{"id":"https://openalex.org/keywords/context-sensitive-grammar","display_name":"Context-sensitive grammar","score":0.5825431942939758},{"id":"https://openalex.org/keywords/tree-adjoining-grammar","display_name":"Tree-adjoining grammar","score":0.5269652009010315},{"id":"https://openalex.org/keywords/indexed-grammar","display_name":"Indexed grammar","score":0.5151461362838745},{"id":"https://openalex.org/keywords/nondeterministic-algorithm","display_name":"Nondeterministic algorithm","score":0.48939743638038635},{"id":"https://openalex.org/keywords/phrase-structure-grammar","display_name":"Phrase structure grammar","score":0.4674564003944397},{"id":"https://openalex.org/keywords/discrete-mathematics","display_name":"Discrete mathematics","score":0.38345032930374146},{"id":"https://openalex.org/keywords/combinatorics","display_name":"Combinatorics","score":0.331781804561615},{"id":"https://openalex.org/keywords/computer-science","display_name":"Computer science","score":0.271431028842926},{"id":"https://openalex.org/keywords/decidability","display_name":"Decidability","score":0.21383342146873474},{"id":"https://openalex.org/keywords/natural-language-processing","display_name":"Natural language processing","score":0.19029134511947632}],"concepts":[{"id":"https://openalex.org/C192034797","wikidata":"https://www.wikidata.org/wiki/Q3502995","display_name":"Undecidable problem","level":3,"score":0.7451958060264587},{"id":"https://openalex.org/C2780069185","wikidata":"https://www.wikidata.org/wiki/Q7977945","display_name":"Equivalence (formal languages)","level":2,"score":0.7274892330169678},{"id":"https://openalex.org/C97212296","wikidata":"https://www.wikidata.org/wiki/Q338047","display_name":"Context-free grammar","level":3,"score":0.6545616388320923},{"id":"https://openalex.org/C33923547","wikidata":"https://www.wikidata.org/wiki/Q395","display_name":"Mathematics","level":0,"score":0.6177360415458679},{"id":"https://openalex.org/C53893814","wikidata":"https://www.wikidata.org/wiki/Q7378909","display_name":"Rule-based machine translation","level":2,"score":0.6086971759796143},{"id":"https://openalex.org/C125950753","wikidata":"https://www.wikidata.org/wiki/Q908674","display_name":"Context-sensitive grammar","level":4,"score":0.5825431942939758},{"id":"https://openalex.org/C134083981","wikidata":"https://www.wikidata.org/wiki/Q1754022","display_name":"Tree-adjoining grammar","level":4,"score":0.5269652009010315},{"id":"https://openalex.org/C79243999","wikidata":"https://www.wikidata.org/wiki/Q6590011","display_name":"Indexed grammar","level":5,"score":0.5151461362838745},{"id":"https://openalex.org/C176181172","wikidata":"https://www.wikidata.org/wiki/Q3490301","display_name":"Nondeterministic algorithm","level":2,"score":0.48939743638038635},{"id":"https://openalex.org/C29184939","wikidata":"https://www.wikidata.org/wiki/Q1134367","display_name":"Phrase structure grammar","level":4,"score":0.4674564003944397},{"id":"https://openalex.org/C118615104","wikidata":"https://www.wikidata.org/wiki/Q121416","display_name":"Discrete mathematics","level":1,"score":0.38345032930374146},{"id":"https://openalex.org/C114614502","wikidata":"https://www.wikidata.org/wiki/Q76592","display_name":"Combinatorics","level":1,"score":0.331781804561615},{"id":"https://openalex.org/C41008148","wikidata":"https://www.wikidata.org/wiki/Q21198","display_name":"Computer science","level":0,"score":0.271431028842926},{"id":"https://openalex.org/C153269930","wikidata":"https://www.wikidata.org/wiki/Q430001","display_name":"Decidability","level":2,"score":0.21383342146873474},{"id":"https://openalex.org/C204321447","wikidata":"https://www.wikidata.org/wiki/Q30642","display_name":"Natural language processing","level":1,"score":0.19029134511947632}],"mesh":[],"locations_count":1,"locations":[{"id":"doi:10.1016/s0022-0000(73)80002-9","is_oa":false,"landing_page_url":"https://doi.org/10.1016/s0022-0000(73)80002-9","pdf_url":null,"source":{"id":"https://openalex.org/S141020589","display_name":"Journal of Computer and System Sciences","issn_l":"0022-0000","issn":["0022-0000","1090-2724"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310320990","host_organization_name":"Elsevier BV","host_organization_lineage":["https://openalex.org/P4310320990"],"host_organization_lineage_names":["Elsevier BV"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Journal of Computer and System Sciences","raw_type":"journal-article"}],"best_oa_location":null,"sustainable_development_goals":[{"display_name":"Quality Education","score":0.7300000190734863,"id":"https://metadata.un.org/sdg/4"}],"awards":[],"funders":[{"id":"https://openalex.org/F4320332502","display_name":"University of California, Los Angeles","ror":"https://ror.org/046rm7j60"}],"has_content":{"grobid_xml":false,"pdf":false},"content_urls":null,"referenced_works_count":7,"referenced_works":["https://openalex.org/W1966515438","https://openalex.org/W2001114061","https://openalex.org/W2010769244","https://openalex.org/W2015908876","https://openalex.org/W2058684880","https://openalex.org/W2081969633","https://openalex.org/W7028570583"],"related_works":["https://openalex.org/W2403874525","https://openalex.org/W37677999","https://openalex.org/W2153803459","https://openalex.org/W1608157979","https://openalex.org/W1970209336","https://openalex.org/W2067980891","https://openalex.org/W1255264663","https://openalex.org/W2792956200","https://openalex.org/W1998938240","https://openalex.org/W2143932650"],"abstract_inverted_index":null,"counts_by_year":[],"updated_date":"2026-03-10T14:07:55.174380","created_date":"2025-10-10T00:00:00"}