A Grammar-Based Semantic Similarity Algorithm for Natural Language Sentences

Table 1

Selected linkages used in the algorithm; superscript 𝜉 denotes the optional linking types.

Links	Subtypes	Descriptions
𝐴	—	𝐴 connects pre-noun adjectives to nouns, such as “delicious food” and “black dog”.
𝐴𝑁	—	𝐴𝑁 connects noun-modifiers (singular noun) to nouns, such as “bacon toast” and “seafood pasta”.
𝐵	𝐵𝑠; 𝐵𝑝	𝐵 connects noun to a verb in restrictive relative clauses, and 𝐵𝑠 and 𝐵𝑝 are used to enforce noun-verb agreement in subject-type relative clauses (relative clauses without “,”), such as “He will see his son who lives in New York”.
	𝐵𝑠𝑑	𝐵𝑠𝑑 is used for words “*ever” like “whatever” and “whoever”.
	𝐵𝑠∗𝑤	𝐵𝑠∗𝑤  is used for object-type questions with words like “which", “what", “who," and so forth.
𝐷	𝐷𝑠	𝐷 connects determiners to nouns, 𝐷𝑠 connects singular determiners like “a”, “one” to nouns, such as “a cat”, “one month.”
	𝐷𝑚𝑐	𝐷𝑚𝑐 connects plural determiners like “some”, “many” to countable nouns.
	𝐷∗𝑢	𝐷∗𝑢 connects mass determiners to uncountable nouns.
𝐷𝐷^𝜉	—	𝐷𝐷 is used to connect definite determiners like “the”, “his”, “my” to number expressions and adjectives acting as nouns, such as “my two sisters”.
𝐷𝐺^𝜉	—	𝐷𝐺 is used to connect “the" with proper nouns.
𝐷𝑇^𝜉	𝐷𝑇𝑖	𝐷𝑇 is used to connect determiners with nouns in certain idiomatic time expressions, such as “last week" and “this Tuesday". 𝐷𝑇𝑖 connects time expressions like “next”, “last” to nouns.
	𝐷𝑇𝑛	𝐷𝑇𝑛 connects time expressions like “this”, “every” to nouns, such as “every Sunday”.
𝐺𝑁	—	𝐺𝑁 connects expressions where proper nouns are introduced by a common noun, such as “the famous physicist Edward Witten”.
𝐽	∗	𝐽 connects prepositions to their objects. Proper nouns, common nouns, accusative pronouns, and words that can act as noun-phrases have “𝐽” link.
𝐽𝐺^𝜉	—	𝐽𝐺 connects prepositions like "of" and "for" to proper-nouns, such as “the WIN7 of Microsoft”.
𝑀	𝑀𝑝	𝑀 connects nouns to postnominal modifiers such as prepositional phrases, participle modifiers, prepositional relatives, and possessive relatives, in which 𝑀𝑝 works in prepositional phrases modifying nouns.
𝑀𝐺	—	𝑀𝐺 allows certain prepositions to modify proper nouns, such as the above sentence.
𝑀𝑋^𝜉	∗	𝑀𝑋 links nouns to postnominal noun modifiers surrounded by commas, such as “the teacher, who…”
𝑂^𝜉	∗	𝑂 connects transitive verbs to nouns, pronouns, and words that can act as noun-phrases or heads of noun-phrases, such as “told him”, “saw him”.
𝑅	—	𝑅 is used to connect nouns to relative clauses, such as “The man who…”.
𝑆^𝜉	𝑆𝑠	𝑆 connects subject nouns to finite verbs. The subtype 𝑆𝑠 connects singular nouns words to singular verb, such as “She sings very well”.
	𝑆𝑝	𝑆𝑝 connects plural nouns to plural verb forms, such as “The monkeys ate these apples.”
	𝑆𝑠∗𝑤	𝑆𝑠∗𝑤 is used for question words that act as noun-phrases in subject-type questions, such as “Who is there.”
𝑆𝐼^𝜉	∗	𝑆𝐼 is used in subject-verb inversion, such as “Which one do you want.”
𝑈𝑠^𝜉	—	𝑈𝑠 is used with nouns that both satisfy the determiner requirement and subject-object requirement, such as “We check that per hour.”
𝑊𝑁	—	𝑊𝑁 connects “when" phrases back to time-nouns, such as “This month when I was in Taipei…”
𝑌𝑃^𝜉	—	𝑌𝑃 connects plural noun forms ending in “s” to “′”, such as “The students’ parents.”