Re: [topicmaps-comment] Topic Maps for Requirements Management?

[Robert Barta <rho@bigpond.net.au>]

On Thu, Dec 27, 2001 at 08:00:53PM -0500, Thomas B. Passin wrote:
> Does anyone have any real information on other kinds of implementations that
> could handle the larger sizes?   How much memory might a map with say 20,000
> topics with maybe 4 occurrences each, and 20,000 associations, take up if it
> were in-memory in a topic map engine (very uncertain, I know, but do you
> think we might be talking about say 5 MB vs 500 MB here?)?

Hmmm, not talking about memory hogs like Java/Perl but in a C implementation
I could imagine the following (very aggressive) calculations:

  - put all topic information (basename, occurrences, ...) into a vanilla
    relational database.

  - leave associations in memory:

      - one association...on average 3 members (role/topic), one scope, one type...
        makes 8 links....store these in 4 bytes, each....32 bytes per assoc.
      - have links bidirectional: 64 bytes per assoc.
      - add tagging for the links +2 bytes per link
      - add administrative infrastructure (list/hash pointers): + 50%
         => under 100 bytes per assoc

20.000 assocs make < 2MB. Even if I assume all sorts of additional data structures
500MB should not be necessary.

Back to Perl: My current Perl implementation (orthodox parallel to XTM) uses 5MB 
for 127 assocs and 231 topics. There is room for improvement, I'd say.

\rho