does it mean, time flies (funny critters, probably out of Star Trek or something) like an arrow? (why they would like an arrow is beyond me, but sure...)

or does it mean, time (you know, as in space-time) flies like an arrow? (recall back to English class - yes, I know you slept through most of it.. anyway, this is a simile)

or even more outrageously, does it mean, time (as a verb; you know, like "time how long it take me to type 'supercalafragilisticexpealidocios' on this Twiddler") flies like an arrow? (time the flies, as if they were an arrow. a totally ludicrous interpretation, but the computer doesn't know that..)

well anyway, you can't know, out of context, what the sentence is supposed to mean, hence the trouble for a Natural Language Processing program