| Chapter 2: The Source Text |

| 2.15. Does Inform really understand English?

No. No computer does, and Inform does not even try to read the whole wide range of text: it is a practical tool for a particular purpose, and it deals only with certain forms of sentence useful to that purpose. Inform source text may look like "natural language", the language we find natural among ourselves, but in the end it is a computer programming language. Many things which seem reasonable to the human reader are not understood by Inform. For instance, Inform understands

> something which is carried by the player

but not (at present, anyway)

> something which the player carries

even though both are perfectly good English. So it is not always safe to assume that Inform will understand any reasonable instruction it is given: when in doubt, we must go back to the manual.

More philosophically, to "understand" involves contextual knowledge. Just because Inform recognises and acts on a sentence, does it really understand what we meant? It will turn out that Inform is both good and bad at this. For instance, from

> Mr Darcy wears a top hat.

Inform will correctly deduce that Darcy is a person, because inanimate objects do not ordinarily wear clothes, and that the top hat is clothing. But it will not automatically know that Darcy is a man rather than a woman because it does not know the social convention implied by "Mr". Moreover, if instead we had written

> Mr Darcy carries a top hat.

then Inform would not guess that the top hat is clothing. This is because it does not have the vast vocabulary and experience of a human reader: it is probably discovering the word "hat" for the first time.

Finally, it is best to avoid ambiguities rather than rely on Inform to know which meaning is patently absurd. For instance, in

> Heatwave bone breaks clog hospital.

(a headline once printed by the Oxford Mail newspaper) a human reader quickly realises that there is no clog hospital being broken. But if Inform had been taught the verbs to break and to clog then that is exactly the conclusion it would have drawn. Or an example which genuinely arose in beta-testing:

> The life support unit fits the egg.

in which Inform construed the verb as support and not fits, and then created items called "the life" (plural) and "unit fits the egg".

That disclaimer completes the groundwork, and we are ready to begin on simulating a world to explore.

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