In order to reuse some POJOs, I followed the procedure defined in
http://mswiderski.blogspot.com/2014/02/reuse-your-business-assets-with-jbpm-6.html
and added a POJO to the "reusable project" (named Papito)

Everything works fine the first time one uses those clases in the "top project" (named Hijita) . POJOs of the "reusable project" are prefixed with the string "- ext -" in the Java editor of the "top project" just as explained in "15.7.6.6.3. Using the external objects" of the document:
http://docs.jboss.org/drools/release/6.1.0.Final/drools-docs/html/wb.Workbench.html#wb.DataModeller

The problem is that only happens the first time. If one logout and the login again, the "-ext" classes are no longer shown as valid Types por the POJOs in the "top project"