Re: [igraph] GraphML graph format

[Tamas Nepusz]

Hello,

On 11/27, Massimo Franceschet wrote:
> I am using igraph "0.7.1" from R interface. I noticed that when I read
> a graph in GraphML, an additional id attribute is created for nodes in the
> igraph graph, even if there exists no GraphML id attribute for nodes. This
> might create problems if there exists already an id attribute for nodes in
> the igraph graph.
Please see the following thread on this mailing list:

http://lists.nongnu.org/archive/html/igraph-help/2014-09/msg00003.html

The executive summary is:

- some people actually expect that the "id" attribute of GraphML <node> tags
  appears as a vertex attribute when the graph is loaded so we convert it to
  a real vertex attribute if there is no such vertex attribute among the <data>
  tags
- right now we give a warning and then _ignore_ the "id" attributes if there is
  a "real" id attribute among the <data> tags. In this case the current version
  gives a warning, but this has confused quite a few people so the warning will
  be gone in the next version
- the important thing is that if you used a vertex attribute named "id" that
  stores your own data, this is preserved when you save the graph in GraphML
  and then load it back later.

All the best,
T.