Subject: [TS] Topic maps
From: Ben Darnell (bgdarnel@unity.ncsu.edu)
Date: Thu Mar 02 2000 - 17:47:56 EST
Here are my thoughts on various aspects of topic maps, particularly
where they differ from ThoughtStream.
1: Scopes
Scopes are essentially a way to resolve name collisions. For example, a
topic map may have two topics named "Washington", one in the scope of
"City" and the other in the scope of "State". A user may specify a
scope while searching a topic map in order to reduce the number of hits
returned.
ThoughtStream can currently simulate this by using links. Is it
necessary to add a special case for this? One argument in favor of
treating scopes specially is that there may be a large number of "City"
ideas in a mind, so that the idea named "City" become overwhelmed by the
number of links. It is a hub linking to each individual city, but any
information specific to the "City" node is drowned out. On the other
hand, topic map scopes are used as a filter over search results, while
link-based scopes could be used to improve the efficiency of the search.
2: Formally-defined link types
Currently in ThoughtStream, there are the Parent/Child and Jump/Jump
link types, and a user-specified label for each end of a link. In Topic
Maps, a link type is itself a topic. This lets you define attributes of
a link. For instance, one could declare that "located in" is
transitive, and then this information could be used in searches or other
operations.
I like this concept, but I'm not sure if I want to clutter the idea
namespace with metadata like this.
3: Out-of-line links
Associations between topics are stored outside of the <topic> element.
I think that inline links are preferable whenever possible (i.e.
whenever it is possible to modify both ends of the link), especially on
CPU- and memory-limited devices such as Palms. This is an
implementation detail, but it also matters on a higher level - in
ThoughtStream, you can[1] arrange links, notes, and other items in any
order within an idea. In XTM, the order of links and notes relative to
each other would be lost (order within a class of items could be
preserved, but is not guaranteed).
4: External data
Information is stored in a topic map in two ways - associations, which
link two (or possibly more? the spec wasn't clear on this) topics, and
occurences, which are links to documents outside the topic map. In TS,
information can be stored within the idea in the form of notes or other
data items. There doesn't seem to be any way in the standard topic map
format to cram this sort of data into the topic map.
That's all for now. Feedback is always welcome.
-Ben
-- Ben Darnell bgdarnel@unity.ncsu.edu http://thoughtstream.org------------------------------------------------------------------------ Luck o' the Irish! Get your St. Paddy's day party supplies at GreatEntertaining.com today. Green salami, brew kits, shamrock confetti, gold coins, & more. Erin Go Bragh! http://click.egroups.com/1/2042/3/_/6321/_/952037294/
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