[xsd-users] Help on parsing GML

[Olivier Tournaire]

Thank you Boris for your answer.

Finally, I choose to parse a CityGML file instead of a GML one. I 
generate the C++ code from the CityGML 0.4.0 schema with this command line :

xsd cxx-tree  --generate-polymorphic --generate-doxygen --namespace-map 
http://www.citygml.org/citygml/1/0/0=CityGML --namespace-map 
urn:oasis:names:tc:ciq:xsdschema:xAL:2.0=urn_oasis_names_tc_ciq_xsdschema_xAL_2_0 
CityGML.xsd

Then, thanks to your tips, I wrote this small piece of code :

#include <iostream>
#include <fstream>
#include <string>
#include <memory>

#include "CityGML.hxx"

int main(int argc , char** argv )
{
    std::string filename("C:\\Documents and 
Settings\\Olivier\\Bureau\\FZK-House_LOD1\\FZK_Haus_LOD1.gml");
    std::ofstream log("log.txt");

    try
    {
        log << "Parsing file " << filename << std::endl;
        std::auto_ptr<CityGML::CityModelType> r ( 
CityGML::CityModel(filename) );
        log << "File parsed with success !" << std::endl;

        
CityGML::CityModelType::_GenericApplicationPropertyOfCityModel_iterator 
iterator_begin, iterator_end;
        
CityGML::CityModelType::_GenericApplicationPropertyOfCityModel_sequence 
seqCity = r->_GenericApplicationPropertyOfCityModel();
        iterator_begin = seqCity.begin();
        iterator_end = seqCity.end();
    }
    catch (const xml_schema::exception& e)
    {
        log << "Error parsing file !" << std::endl;
        log << e << std::endl;
        log.close();
        return EXIT_FAILURE;
    }

    log.close();
    return EXIT_SUCCESS;
}

Here are the first lines of the CityGML file :

<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated by:                                    -->
<!-- IFC -> CityGML Converter                         -->
<!-- (C) - Institute for Applied Computer Science     -->
<!-- Forschungszentrum Karlsruhe                      -->
<!-- Not for commercial use                           -->
<!-- Generated by: IfcExplorer-->
<!-- Level of Detail 1-->
<!-- Creation Date: Friday, 10 November 2006 - 13:20:59-->
<CityModel xmlns="http://www.citygml.org/citygml/1/0/0" 
xmlns:gml="http://www.opengis.net/gml" 
xmlns:xlink="http://www.w3.org/1999/xlink" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://www.citygml.org/citygml/1/0/0 
http://www.citygml.org/citygml/1/0/0/CityGML.xsd">
  <gml:name>AC90-FZK-Haus-2x3-63020_</gml:name>
  <gml:boundedBy>
    <gml:Envelope>
      <gml:pos srsDimension="3">3458643.83172578 5440407.10899672 
-1</gml:pos>
      <gml:pos srsDimension="3">3458665.08225378 5440425.41250692 
6.3176914694611</gml:pos>
    </gml:Envelope>
  </gml:boundedBy>
...
...
...

I use VC 2003, so, I turn RTTI. Then, everything compiles fine, with 
only 4 warnings related to the maximum number of lines the compiler can 
support (CityGML.hxx and CityGML.cxx are very very very long). Then, I 
run the program, and everything went well.

No, I would like to know how can I access for example the tag 
<gml:name>AC90-FZK-Haus-2x3-63020_</gml:name> ? I am able to obtain a 
const iterator to a sequence of _GenericApplicationPropertyOfCityModel. 
Then, back to CityGML schema, I found these line :

<xs:element name="_GenericApplicationPropertyOfCityModel" 
type="xs:anyType" abstract="true"/>

So, dereferencing iterator_begin, I obtain a xml_schema::type which is a 
typedef for ::xsd::cxx::tree::type. However, I do not know what to do 
with that stuff ...

Here is an other line I found in the CityGML schema :

<!-- =======================================CityModel Members  
================================== -->
    <!-- 
========================================================================================= 
-->
    <xs:element name="cityObjectMember" type="gml:FeaturePropertyType" 
substitutionGroup="gml:featureMember"/>

I tried this, but it does not compile :

for (;iterator_begin!=iterator_end;iterator_begin++)
        {
            if ( dynamic_cast<gml::FeaturePropertyType *>( 
(*iterator_begin).pointer ) == true )
                ; // ...
        }

error C2039: 'pointer' : n'est pas membre de 'xsd::cxx::tree::_type'

Please could you help me ?

Best regards

Olivier Tournaire

Boris Kolpackov a écrit :
> Hi Olivier,
>
> Olivier Tournaire <olivier.tournaire at gmail.com> writes:
>
>   
>> First, as I am not familiar with GML, I would like to have a small
>> sample with, for example, only points. Could you help me ?
>>     
>
> A better place to look for GML document samples would be on the GML
> publisher's website:
>
> http://www.opengeospatial.org/
>
> They also have a forum dedicated to GML where you can ask GML-related
> questions.
>
>
>   
>> Then, xsd cxx-tree generated a lot of C++ classes, and I do not know
>> where to begin. What object do I have to declare in order to parse a GML
>> file?
>>     
>
> First, I strongly recommend that you read through the C++/Tree Mapping
> Getting Started Guide:
>
> http://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/guide/
>
> This should give you an idea on how to parser and access GML documents.
> Generally, you would first identify the document's root element by
> looking at your sample documents (let's say it is called 'root'). Then
> you would look for a declaration of this element in the schema and
> determine its type (let's say it is 'type'). Based on this information
> you can then write:
>
> auto_ptr<type> r = root ("sample.xml");
>
> Boris
>
>   

-- 
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