I'm a new user of WildFly, and I've spent quite a while figuring out that I apparently shouldn't delete the ExampleDS from my server instance. Once I deleted it:

• My own DataSources could no longer access the H2 driver
• My applications could no longer access their own datasources (even unmanaged ones)
• My applications could no longer be undeployed or redeployed

The only workaround I found was to completely re-install the entire server.

Now, I still don't completely understand the point of this ExampleDS, but I'll just leave it where it is and never touch it again. If this is some internal DataSource that is needed for JavaEE 7 compliance as suggested by Roberto Cortez in this Tweet:
https://twitter.com/radcortez/status/539394425370443776

... then I would suggest completely hiding it from the Web Console UI and making it an internal system thing that I'm not going to be concerned with.