[gdal-dev] Internal Metadata Management

[Frank Broniewski]

Hello,

I have a question concerning OGR's metadata or attribute management when 
converting between geodata vector formats. My question is maybe only 
loosely related to OGR and aims at the internal management of attribute 
data.

 From what I have read and understood from the documentation, OGR uses 
the OGC Simple Feature Specifiaction to transform data from one format 
to another. While reading the OGC specs I could not find a notion on how 
one should deal with attribute metadata, the whole spec seems to be 
about vector geometries only.

Why I ask this: I am a Python user using the ogr python bindings and now 
the need arose that I need to write a flexible geo format exchange 
software. I chose OGR as a base for doing the conversion. My data often 
comes from databases with non standard data and geoemtry formats. So I 
want to align with OGR's internal used Simple Feature Data format, but I 
don't know how/where I should put the attributes / metadata. I see that 
the Feature is the part I have to look at because it has the geometry 
and the FeatureDfn. Unfortunately this is the part I don't understand :-)
I need to create a FeatureDfn for my Feature which is basically the 
column names and data types? Where do I put my attribute values then? I 
looked at the OGRFeatureDefn Class Reference, but my understanding of 
OGR is too low to understand how this relates to the OGRFeature.

So basically I am looking for a starter tip that pushes me into the 
right direction. Is there some python tutorial somewhere which I missed 
or somebody has a code snippet for me?

Or would it be easier to use internally a format like geojson and use 
this as a starter for converting to other formats? Can OGR always 
transfer the attributes of my geospatial data to other formats?

I am sorry that my question is somewhat unclear, but I have some 
difficulties to find the right form for my question. But I hope that I 
could state my problem in an understandable way :-)

Many thanks for any tipps

Frank