The only free search tool generally available is WAIS which, while
not bad, is kind of difficult to administer and does not mate well
with SGML.
But then, there are very few *commercial* search tools that mate well
with SGML either. So to get what you want, you'll probably have
to write it.
Since I am a tired old full-text-search guy, Lark takes fanatical care
to keep track of the byte offsets of everything; so there will be at
least one parser that would be useful in such an effort. The fact
that Lark doesn't look at DTD's nor check conformance is not an
issue at indexing time.
>I would also intend to use a graphically-based query if possible as well
>as a commandline. Has this been tried and are there any metaphors which
>have proved to be useful? How do most humans currently construct TEI
>quries? Do they learn the language and use a command line or do they
>get customised queries?
I've never seen a graphical search query GUI that was useful.
- Tim