Hey Stefano,
Welcome to the community. The validation error you are seeing is actually just a bit of Eclipse weirdness and can be remedied by following the second note on the Tooling Install guide to disable "Honour all XML schema locations":
https://docs.jboss.org/author/display/SWITCHYARD07/Installing+Eclipse+Tooling
Next question I have is if you have a specific reason to start with BPEL? If your aim is to get familiar with the project with a minimal amount of fuss, you might find Java and Camel to be easier at first. Of course, if you are experienced with BPEL and have decided to start there, that's cool too. I mention this only because BPEL has a fair number of moving parts, so the level of complexity necessarily goes up compared to something easy like Camel. :-)
Assuming we are still on the BPEL train at this point, then I would point out that Rob has done quite a bit of work in our 0.8 release to make the BPEL tooling easier to use. You can find a lengthy discussion on it here:
https://community.jboss.org/thread/220845?start=0&tstart=0
Please throw in your thoughts on that thread if you have additional suggestions. The final tooling for 0.8 will be ready in about a week, but you can grab a nightly build of the tooling and the runtime for 0.8 if you want to go that route.
Lastly, there is not a new BPEL how-to specifically for SY at this point, although I think that would be useful. I'm in the process of overhauling our documentation for 0.8 and will try to include as much info as I can to help new users get started. If you are using 0.7, I would use the BPEL quickstarts as a learning tool and maybe as a template for new processes. You can find the quickstarts in the distribution and here as well:
https://github.com/jboss-switchyard/quickstarts/tree/master/bpel-service
hth,
keith
