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L15 Selectional restrictions Selectional Restrictions & Semantic Attributes o Selectional restrictions are semantic constraints placed on arguments of a verb. + Ex.: The fork ate the carrot. - Violates semantic constraint: Only animate beings can eat. - Fork is not animate. o Example constraint + Eat ROLE SEMANTIC FEATURE * agent +animate * theme +edible - Meaning: * Object which can be filler of agent role must be animate. * Filler of theme must be edible. o Requires putting semantic features with every noun. Ex. features: living being, edible, etc. - Nouns: 30000 upwards for reasonable system (Contrast with number of verbs: 3000) * To put semantic features with nouns is a large task o Selectional restrictions help in disambiguation * Identifying roles + Ex.1: He opened the lock with the key. + Ex.2: He opened the lock with the yellow color. - In Ex.1, key is instrument, but yellow color is not. * Selecting word sense + Ex.1: He drinks milk + Ex.2: My car drinks petrol - Sense of 'drink' in Ex.2 is excessive consumption...........................................NEXT PREVIOUS INDEX