Questions - meta-questions about knowledge representation

Here are some meta-questions (background questions about the why and foundations) and devil's advocate questions that are not often (?) asked, but helpful for non-specialists, students, and I assume even experts. Note, I know some answers the following, but I would like to see the answers of others. Also, some answers i'm aware of are superficial, so hopefully we can have more substantive ones here.

Context:

- When I studied knowledge representation and reasoning (KRR) and philosophy of AI, KRR was presented as one topic in AI. And symbolic and non-symbolic approaches were mentioned.

1) Are there non-symbolic approaches to KRR?
(Approaches that do not use symbolic logics?)

If so, what are they, and what are the pro's and con's of both (non)symbolic KRR?
(it may be helpful to define what you mean by symbolic and non-symbolic if different from the use of FOL and other logics)

2) Why use formal/symbol logics such as first-order predicate calculus (or others)?
Do you have quantitative evidence for the benefits of them?
Can you give examples of successful projects that publicize quantitaitve evidence for the benefits?

3) What are alternatives for KRR techniques for achieving the same goals KRR aims to?

4) Do you have quantitative evidence for the utility of KRR in general?

5) ...add your own meta-level questions...

NOTE: I've seen answers to 2 & 4 are often found as qualitative descriptions, buzz-phrases, or hand-waving (like in many disciplines) but without clear and specific quantiattive evidence. So please focus on that. Quantiative evidence may involve: showing increases in efficiency of this or that computational process, (by the numbers), etc.

Thanks.

Roberto
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