What does 'as' mean when followed by v-ing?

Question

I need help in fully comprehending the sentence below. Please take a look and thanks in advance. :)

-From a passage about Semiotics

"Various typologies of signs have been proposed, but three fundamental classes of signs seem to stand out as requiring different approaches: the icon, the index, and the sign proper."

What does 'as requiring different approaches' mean? I can understand the sentence only up to the point where it says 'but three..stand out'.

1. What is requiring what?

2. Can I replace 'as requiring' to 'which requires'? If not, how can I say this confusing part differently?

3. Is as + v-ing certain usage of 'as'?

Answer 1

The more interesting phrase here is "[In the context of Ns], N stands out as A", where N is a noun that is part of Ns, and A is an adjective or adjective-like phrase. Here are some examples:

• In the history of ethics Bentham stands out as one of the ablest champions of utilitarianism.
• The year 1880 stands out as one of manifold misfortune and disaster to agricultural Russia.
• You want to stand out as the best applicant the hiring committee has ever seen.
• Some of the great fairy tales stand out as answering to this test.

The phrase indicates that N is particularly A in the context. In your example:

1. What requires what? The "classes...require...approaches".
2. If you replace 'as requiring' with 'which require', it would imply that they really "stand out" more. A different phrasing closer to the original meaning might be "there seem to be three fundamental classes that clearly require different approaches".
3. as+v-ing is not a fruitful analysis in this case, both because "as" is part of the phrase "stands out as", and because "requiring different approaches" is adjective-like.

Answer 2

To "stand out as requiring X" means to stand out because of the fact that they require X.

In your sentence: the icon, the index, and the sign proper stand out among fundamental classes of signs because they require different approaches.

No, you can't replace "as requiring" by "which requires". Replacing it by "because they require" would be closer to the mark.