Re: [libxml++] Searching nodes with ns prefix

[togol m. <tog...@ly...>]

Thanks for the prompt reply.

If I am searching for an element not in the default namespace, then there s=
hould no error messages regarding namespace registeration. Thats exactly wh=
at is confusing because OWL namespace is not a default namespace as is defi=
ned in the following OWL file.=20

<?xml version=3D"1.0"?>

<!DOCTYPE rdf:RDF [
  <!ENTITY root                 "file:/C:/OntoCAPE/">
  <!ENTITY owl                  "http://www.w3.org/2002/07/owl">
  <!ENTITY xsd                  "http://www.w3.org/2001/XMLSchema">
  <!ENTITY rdf                  "http://www.w3.org/1999/02/22-rdf-syntax-ns=
">
  <!ENTITY rdfs                 "http://www.w3.org/2000/01/rdf-schema">
  <!ENTITY molecular_species    "&root;molecular_species.owl">
  <!ENTITY phase_system         "&root;phase_system.owl">
  <!ENTITY Example              "&root;Example_v1.owl">
  <!ENTITY substance            "&root;substance.owl">
]>

<rdf:RDF
    xmlns=3D"&Example;#"
    xmlns:rdf=3D"&rdf;#"
    xmlns:rdfs=3D"&rdfs;#"
    xmlns:xsd=3D"&xsd;#"
    xmlns:owl=3D"&owl;#"
    xmlns:molecular_species=3D"&molecular_species;#"
    xmlns:phase_system=3D"&phase_system;#"
    xmlns:substance=3D"&substance;#"
    xml:base=3D"&Example;"
>
=20
  <owl:Ontology rdf:about=3D"&Example;">
    <owl:imports rdf:resource=3D"&phase_system;"/>
    <owl:imports rdf:resource=3D"&molecular_species;"/>
  </owl:Ontology>

Now if I find the ontology node with the XPath expr "//owl:Ontology", the n=
amespace registration error is thrown. If I explicitly register the OWL nam=
espace using xmlXPathRegisterNs function, the error message does not appear=
 but the node set is still empty. It does not change even if I replace xmln=
s:owl=3D"&owl;#" by xmlns:owl=3D"http://www.w3.org/2002/07/owl".=20

Togol=20

----- Original Message -----
From: "Darko Miletic" <da...@uv...>
To: "togol machillan" <tog...@ly...>
Subject: Re: [libxml++] Searching nodes with ns prefix
Date: Sun, 16 Oct 2005 14:38:34 -0300

>=20
> togol machillan wrote:
> > Dear Members,
> >
> > I am facing the problem of finding nodes in an OWL file. The=20
> > importance of registering the namespace before calling the find()=20
> > function has been discussed before, but still the find function=20
> > in libxml++ v2.12 does not support this. I defined a new function=20
> > as follows.
> > The "undefined namespace prefix" error message does not appear=20
> > anymore, but the node set is still empty. I call the find()=20
> > function for the root node rdf:RDF of the owl document with the=20
> > XPath expr //owl:Ontology. If I add a check to see whether the=20
> > OWL namespace is already registered using xmlSearchNs(), it=20
> > returns the namespace pointer since for OWL, the namespace is=20
> > always defined in the root node. Can somebody please point out=20
> > where the problem is?
>=20
> Namespace needs to be registered ONLY if it is default namespace.=20
> Other namespaces are recognized properly. That means if you have=20
> xml file like this:
>=20
> <?xml version=3D"1.0" encoding=3D"UTF-8"?>
> <rootitem xmlns=3D"http://www.something.com/ns1"
>                   xmlns:xsi=3D"http://www.w3.org/2001/XMLSchema-instance"
>                   xsi:schemaLocation=3D"http://www.something.com/ns1 ns1.=
xsd"
>   version=3D"1.3">
>=20
> In this case you must register ns1.xsd before doing find. For=20
> example like this:
>=20
>        xmlXPathRegisterNs( ctxt,
>                            "ns1",
>                            "http://www.something.com/ns1");
>=20
> The when doing search you should prefix all nodes from default=20
> namespace with namespace name you registered:
>=20
>    node->find("//ns1:rootitem/otheritem");
>=20
> Not placing registered prefix for default namespace in xpath string=20
> is the most common error when using libxml++ or libxml2.
>=20
> Darko
>=20
>=20
>=20
> -------------------------------------------------------
> This SF.Net email is sponsored by:
> Power Architecture Resource Center: Free content, downloads, discussions,
> and more. http://solutions.newsforge.com/ibmarch.tmpl
> _______________________________________________
> Libxmlplusplus-general mailing list
> Lib...@li...
> https://lists.sourceforge.net/lists/listinfo/libxmlplusplus-general


--=20
_______________________________________________

Search for businesses by name, location, or phone number.  -Lycos Yellow Pa=
ges

http://r.lycos.com/r/yp_emailfooter/http://yellowpages.lycos.com/default.as=
p?SRC=3Dlycos10