Dec1999 CO230 : Cognitive Science (Question 5)Suggested Solutions

(a)

Briefly describe each of the three processing stages of language analysis:parsing , semantic interpretation and expanded representation .Describe the output from each stage.

(i)Parsing:

•Analyses the input to determine syntactic structure;Provides a framework for semantic representation by identifying the relations of the components of the sentence.(1)for either of these two points.

•The output is often represented as a parse tree (1).

(ii)Semantic interpretation:

•Relates knowledge of the meanings of words and linguistic structure to the parse tree (1).

•The output is a representation of the meaning of the sentence;Common methods of representation include conceptual graphs,conceptual dependencies frame and logic based representation.(1)for either of these two points.

(iii)Expanded representation:

•Adapts the meaning of the sentence according to stored knowledge about the real world (1)

•The output is the meaning of the sentence within its proper context.(1)

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(b)

All languages can be treated as symbolic systems that can be easily handled by computers.

(i)Describe why natural languages can be considered as symbolic systems . [2 marks ]

Accept other valid answers; A maximum of 2 marks from the following:

•Each individual sound or word in language can function as a symbol which signifies a particular meaning.(1)

•These symbols can be combined in various ways to give an infinite number of sentences, each represented by a sequence of symbols.(1)

•Linguistic rules (as defined by a grammar)can be applied to the symbolic representation of the sentences to determine whether they are valid (and therefore meaningful)or not.(1)

(ii)Describe how computers handle natural languages as symbolic systems. [3 marks ]

Accept other valid answers;A maximum of 3 marks from the following:

Most computers are symbolic processors capable of storing a large number of linguistic symbols in the memory thus allowing fast searches and retrieval (1). The symbols can be manipulated to produce sentences by the use of operators (eg. iteration,recursion) (1).The computer can easily check the symbolic representation of sentences for syntactic correctness (1)by matching them against grammatical rules (1).The symbolic representation of languages allows inference rules to be used to discover meanings of sentences (1).

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(c)

Language analysis is typically broken down into seven levels,of which world knowledge analysis is the final level in the process.

In the sentence “Fruit flies like bananas ”,this final world knowledge analysis is important for correct processing of the sentence at the earlier levels of analysis. Explain why this is the case.[4 marks ]

The sentence can be interpreted in two ways:

•In the morphological and syntactic levels,if we treat “fruit ”as a noun and “flies ” as a verb,then we have a sentence that allows us to imagine fruits flying like bananas.(1)The real word knowledge analysis level is required to determine that this interpretation is unlikely to make sense:we know that fruits and bananas do not fly (at least,not unless they are thrown!).(1)

•On the other hand,if the morphological and syntactic levels treat “fruit flies ”as a noun,then the interpretation will be that fruit flies have a liking for bananas.(1) From real world knowledge,we know that bananas are fruits and fruit flies (as a noun)like fruit,so this interpretation is more likely to be correct.(1)

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