Sample file for the XSLT stylesheet

[StefanCiesilski]

Hello,
Is there a sample file for the XSLT stylesheets? I wanted to convert City Objects into another City Objects.

Thanks
Stefan

[clausnagel]

There are in fact no XSLT examples in the citygml-tools download package. I guess this should be changed. You can find two examples in thecitygml4j repo at: https://github.com/citygml4j/citygml4j/tree/master/citygml4j-samples/input/stylesheets.

1. AddressRemover.xsl removes address properties from CityGML 2.0 buildings.
2. CoordinateFormatter.xsl formats coordinates of CityGML 2.0 features so that each coordinate has exactly three decimal places.

I hope they can serve as a starting point. There are some general rules you have to follow:

1. Be precise with XML namespaces in your XSLT to make sure that you process the correct XML elements and attributes. Each CityGML version uses different namespaces for its modules.
2. citygml-tools applies the XSLT to each top-level feature in a CityGML file (i.e., the child elements below <cityObjectMember>). This is because each file is read and written chunk-wise, with top-level features being the individual chunks. So, do not use XPath expressions starting from the root <CityModel> element.
3. The first chunk you get is the root <CityModel> element with its attributes excluding, of course, all <cityObjectMember> elements. So, you can access and change the attributes of the <CityModel> but not really the <CityModel> itself.
4. You can use XSLT versions 1.0 and 2.0. Version 3.0 is, however, not supported by citygml-tools.

As explained above, points 2) and 3) are a result of the chunk-wise processing approach used by citygml-tools. The benefit of this approach is that you can apply XSLT to even very large CityGML files. The drawback is that you cannot really change the root <CityModel>. If the latter is important for you use case, you should better use another XML tool to apply your XSLT (which, however, will most likely face file size restrictions).

[StefanCiesilski]

@clausnagel Thanks for the tip!
The first attempt works reasonably well. The validate option does not give any errors...
An upgrade to CityGML 3.0 with additional xlst transformation is not possible, or? I have now executed it separately.

bldg2brid.zip

[clausnagel]

Yup, your XSLT looks fine and reasonably simple. There are generally more building attributes you need to take care of when converting a building to a bridge - but you can also skip them if they are not contained in your data. I suppose you are working with German AdV data?

No, the upgrade command does not offer the option to apply XSLT stylesheets. With the current version of citygml-tools, it requires two subsequent calls as you say.

[StefanCiesilski]

Ok. Yes, German AdV data.
In the first step I only removed the building attributes that validate noted. For the first test this is enough.