Add possibility to download graphs in GEXF format

[lehkost]

The CSV format we offer for download is limited in what it can comprise. We should start slowly to build a GEXF export. The first version could just comprise what the CSV comprises, but on top of the IDs also feature the labels, i.e., character names from <persName> (or, <name>, for person groups). – Here is an easy example how to build the GEXF format.

[cmil]

A first version is of GEXF output is now available with 0.24.0. See for example https://dracor.org/api/corpus/ger/play/wieland-alceste/networkdata/gexf. Please test.

[lehkost]

Cool! 🏄 It looks like it works in Gephi, here's Emilia Galotti:

We could easily add weight, I guess, like so:

<edge id="der_prinz|conti" source="der_prinz" target="conti" weight="2" />

And since we collect gender info, we can add it to node properties:

<attvalues>
  <attvalue for="gender" value="FEMALE"></attvalue>
</attvalues>

This is so much better than working with plain CSV, thanks for the swift implementation.

[cmil]

Version 0.25.0 provides both weight and gender.

[lehkost]

Just tested it, seems to work nicely!

One other obvious thing to provide on a per-node basis would be the number of words per character (i.e., everything within <sp>/<p> and <sp>/<l> (including <emph>, but excluding <note> and <stage> within <sp>…).

It would add to our visualisations to align the node sizes with the number of words per character, an aspect we can't visualise at the moment…

[cmil]

@lehkost since the calculation of the number of words may be a bit more complex but at the same time beneficial for other issues let's deal with it in a separately addressable issue.