Allow XPath expressions in RML whose result is a string

[IanEmmons]

When translating an XML file, rml:reference properties in the RML have values that are XPath expressions. If such an XPath expression results in a node or a node-set, all is well. The mapper uses XPath's inherent ability to convert a node-set into a string and then uses that string in the RDF output. However, if the XPath result is of type string, the mapper fails because it is expecting a node-set. This is easily reproduced by wrapping an XPath expression in a string function, like so:

normalize-space(/my/xpath/expression/that/produces/a/node/set)

It would be helpful if the mapper would handle a string result as well as a node-set, because the functions available in XPath are fairly rich and can in many cases sidestep the need for RML function calls.

[DylanVanAssche]

Hi!

Thanks for reaching out!
Do you have a reproducible example with RML rules and some sample data to better understand this issue?
Thanks!

[IanEmmons]

My examples are quite involved with many external dependencies, and therefore difficult to pass along. However, if you take any working example with an XML source, choose an rml:reference in it, and wrap that XPath expression with the normalize-space Path function, you will reproduce the problem.

[DylanVanAssche]

I can now reproduce it and have a fix ready.
Will be available in the next release!

Thanks for your report!

[IanEmmons]

Thanks, that will reduce the number of FNO function calls I need to make in my RML files.