Olaf Hartig wrote:
Hey,
On Sunday 18 October 2009 09:37:14 Martin Hepp (UniBW) wrote:
[...]
So it will boil down to technology that combines (1) crawling and
caching rather stable data sets with (2) distributing queries and parts
of queries among the right SPARQL endpoints (whatever actual DB
technology they expose).
You can keep a text index of the whole Web, if crawling cycles in the
order of magnitude of weeks are fine. For structured, linked data that
exposes dynamic database content, "dumb" crawling and caching will not
scale.
Interesting discussion!
An alternative approach to query federation is the link traversal based query
execution as implemented in the SemWeb Client Lib. The main idea of this
approach is to look-up URIs during the query execution itself. With this
approach you don't rely on the existence of SPARQL endpoints and -even more
important- you don't have to know all the sources that contribute to the query
result in advance. Plus, the results are based on the most up-to-date data you
can get.
Greetings,
Olaf
Olaf,
SemWeb Client [1] should benefit immensely from Sponger URIs.
If the SemWeb Client enables its consuming programs to designate
traversal predicates beyond "seeAlso", even better. I say this because
of the following statement from you "how it works" section: "..look up
any URI y where the graph set includes the triple { x rdfs:seeAlso y }
and x is a URI from the triple pattern. Add retrieved graphs to the
local graph set."
Once you add custom crawl property/predicate designation, the SemWeb
Client library is basically similar to what the Sponger does inside the
Virtuoso Engine [2][3]:-)
Links:
1. http://www4.wiwiss.fu-berlin.de/bizer/ng4j/semwebclient/
2. http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VirtSponger
3. http://docs.openlinksw.com/virtuoso/rdfiridereferencing.html
4.
http://virtuoso.openlinksw.com/Whitepapers/html/VirtSpongerWhitePaper.html
--
Regards,
Kingsley Idehen Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO
OpenLink Software Web: http://www.openlinksw.com
