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Re: Use case: tiger map/census data: have it your way

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 18 Mar 2004 10:23:45 +0200
Message-Id: <92DED703-78B5-11D8-9FBD-000A95EAFCEA@nokia.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: "ext Dan Connolly" <connolly@w3.org>

This seems like a use case intertwined with an implementation

I think it's useful if our use cases are expressed in terms of
the anticipated DAWG recommendation, so that it is clear which
bits are facilitated by the recommendation and which bits are
addressed by other specs/recs, or by client-specific functionality.

Let's presume that this knowledge already is accessible as a big RDF
graph, and that the means of access complies to the DAWG recommendation.

Then this use case seems to intersect

PS-2: Resource discovery; query by example
PS-11: Datatype Value Comparisons, Minimal Operator Set

insofar as what we might expect the DAWG recommendation to cover;
i.e. identify resources having particular characteristics, with
query resolution involving datatype comparisons, and return
descriptions of the matched resources.

It striks me that calculating an area based on a radius of 50 miles
and restricting locations to those within that area seems
like a pretty specialized application -- and such a calculation
would probably be out of scope for a general solution such
as the expected DAWG recommendation.

However, the client could perhaps express the equivalent
geographic area constraints itself by greater than
and less than constraints of the latitude and longitude
values relative to those of Boston. E.g.


A client wishes to identify resources which have a geographical
location within a 50 mile radius of the city of Boston.

The client is aware of a knowledge source from which such
resources might be discovered, based on their latitude
and logitude.

The client first formulates a query to the knowledge
source explicitly asking for a description of the
city of Boston, from which it obtains the latitude and
longitude of boston.

Based on the known geographical formulas, the agent
constructs a set of templates which roughly constrain
pairs of latitude and longitude values to those no more
than 50 miles distant of Boston (the area may be defined
more as a square than a circle in order to reduce the
number of templates) and submits the query
to the knowledge source.

The knowledge source returns a set of zero or more
descriptions of resources which match one or more
of the query templates.


Now, it's clearer what functionality is provided by
the DAWG recommendation and what functionality is
client-specific, but facilitated/enabled/augmented
by the DAWG recommendation.



On Mar 17, 2004, at 20:06, ext Dan Connolly wrote:

> The U.S. Census Bureau provides some really nify data
>   http://www.census.gov/geo/www/tiger/tiger2003/tgr2003.html
> it's public domain.
> I want to do a query like
> 	tell me the lat, lon, name, and type
> 	of everything within 50 miles of Cambridge, MA
> Right now, I have to download all the files, unzip them,
> read a bunch of docs, write some software, blah blah blah.
> I'd like to just look at it as a big RDF graph and issue
> a query.
> Hmm... it's not clear they (the census folks) have motivation
> to offer a query service. But clearly a third party could.
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
> see you at the WWW2004 in NY 17-22 May?


Patrick Stickler
Nokia, Finland
Received on Thursday, 18 March 2004 03:23:46 UTC

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