Why do WSDL contents get reordered after a new method is added?

[Thomas Attwood]

When deploying an existing (large) web service, @WebService, after a change (for example, adding a new web method) we find that the whole generated WSDL contents are reordered - this makes any diffs really difficult to read or understand. 

Why is this?

I'm trying to build an example but I'm not able to replicate it in a smaller way.