I may have "fixed" the build for "Jena IRI".
Having created a temporary job that worked, I deleted the Jenkins job completely and created a new one.
Otherwise it was seeing old files (specifically, a POM with a relative parent; also I had one instance of it reporting a parse error in the parent POM chain ... but I hadn't checked anything in.
The error occurs elsewhere (e.g. Jena_Core) but I've run out of energy to fix that, then the next one and the next one, ....
Deleting the workspace of a job does not fix the problem, nor does a clean checkout.
Slave machine "windows1" looks to be a bad machine to get for a job. But it seems to be the machine you get if you don't restrict the job, possibly it's lightly because it doesn't work very well but I can't gather concrete evidence.
I'm setting jobs to "ubuntu" Sorry about the noise on jena-commits ... Andy