a0d929ca_WSRP_v2_0_Specification__Statement_text
[#] CS140 [Section] 9.2.1.2 [Statement text] 
The value of this portlet URL parameter defines the opaqueValue portion of the Portlet's navigational state the Consumer MUST send to the Producer when the URL is activated. If this parameter is missing, the Consumer MUST NOT supply the opaqueValue portion of the Portlet's navigational state.
WSRP v2.0 Specification
Statement text