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Implementation experience with SiRPAC

From: Janne Saarela <jsaarela@w3.org>
Date: Tue, 08 Sep 1998 18:04:45 +0200
Message-ID: <35F5559D.8167CE31@w3.org>
To: xml-names-issues@w3.org
I wanted to report some experience I have had implementing
the 2-Aug-98 version of the namespaces specification [1]
within the SiRPAC [2] RDF compiler V1.4.

First of all, SiRPAC uses the SAX interface to the XML
document "stream". With each startElement I build up the
document tree and while doing this, I use both an element
and namespace stack. The former manages the element nesting
level and the latter manages namespace declarations by using
Hashtables for each new element level (even through there
were no new namespace declarations).

The hashtable is first built extracting necessary information
from xmlns: attributes. Then, any element and attribute prefix
is expanded by iterating through the namespace Hashtable stack
to find the declaration from the prefix to a namespace URI.

In this way, in the context of parsing RDF, both the element
name and attribute names are expanded by simply concatenating
the namespace URI and the element/attribute name. Thus, the
application, once given the document tree, will not see the
namespace prefixes at all.

Implementing and testing all this took one day. (let's
see how many bugs remain :-)

BTW, in RDF it is beneficial to have a method
getAttributeValue (Namespace, AttributeName)
for an element. In this way, you can easily request,
for example, the "about" attribute value from the namespace
that interests you. Like in the following I do

element.getAttributeValue(RDFSCHEMA, "about");

<RDF xmlns="http://www.w3.org/TR/WD-rdf-syntax#"
     xmlns:foo="foo#"
     xmlns:bar="bar#">
<Description about="http://some.org/some.doc"
             foo:about="rating1"
             bar:about="rating2" />
</RDF>

Janne

[1] http://www.w3.org/TR/1998/WD-xml-names-19980802
[2] http://www.w3.org/RDF/Implementations/SiRPAC/
--
Janne Saarela           | Visiting scientist
Email: jsaarela@w3.org  | World Wide Web Consortium http://www.w3.org/
Received on Tuesday, 8 September 1998 12:04:23 UTC

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