a0d929ca_WSRP_v2_0_Specification__Statement_text
[#] CS137 [Section] 9.2.1.1.3 [Statement text] 
When a portlet URL specifies "resource" for the wsrp-urlType portlet URL parameter, either the wsrp-resourceID portlet URL parameter or a combination of the wsrp-requiresRewrite and the wsrp-url portlet URL parameters MUST also be specified.
WSRP v2.0 Specification
Statement text