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Re: RDF Queries?

From: Arnold deVos <adv@langdale.com.au>
Date: Fri, 8 Oct 1999 09:43:27 +1000
Message-ID: <004f01bf111d$c102c050$ef01a8c0@lakes.com.au>
To: <www-rdf-interest@w3.org>
Cc: <franklin.reynolds@nokia.com>
From: <franklin.reynolds@nokia.com>
> Is the query service intended to be similar to SQL?

No, there is no query language as such.   Each method in the query interface
is a canned query, parameterized by the method arguments.

> Are the functions get_child_values() and get_descendent_values()
> the primary methods for traversing a graph?

More or less.  Single-valued properties are traversed by get_values(),
many-valued properties are traversed by get_child_values().  The word
"child" is perhaps missused, since we are not traversing a tree.

The get_extent_values() method traverses whatever the inverse property of
rdf:type is.

The get_descendent_values() method is a short form for repeated
get_child_values() invokations.

The interface is a compromise between simplicity and efficiency.  In
particular, we kept the fixed cost of each call in mind (e.g network
latency).  It must be possible for an application to obtain a reasonable
amount of information in each operation.  Thus each method returns values
for many properties and, usually, many resources.

I hope that helps,

Arnold deVos
Langdale Consultants
Received on Thursday, 7 October 1999 19:46:09 UTC

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