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
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