I saw a sign today in the bathrooms which neatly illustrates the problem a computer may have understanding a sentence. It said:
Please don’t put paper towels down the toilet as it causes them to become blocked.
If one were to go solely by the rules of grammar, one would be forced to conclude the paper towels would become blocked: “them” is a plural pronoun, meaning it must apply to the plural towels rather than the singular toilet when the sentence is considered in isolation.
With the context people can apply to this sentence, the problem of “them” is resolved; it’s obvious a toilet may become blocked rather than a paper towel so “them” must apply to the toilet even if the grammatical implication is different.
Computers currently try to understand language in isolation, meaning this kind of issue is common: they lack the knowledge it is possible for toilets to block but not paper towels causing them to come to an incorrect conclusion.
Efforts such as MIT’s ConceptNet aim to alleviate this issue by creating common-sense knowledge corpuses. It will be interesting to see what happens when such efforts bear fruit and people work out how to make use of the knowledge they contain. Until then, I believe computers will have grave difficulties understanding everyday speech.