P. 5 All components of the Top-level query are optional. Restriction expression can be either at the query or sub-query level. Attributes are optional. Some implementors will not use attributes at all. Defer to the attribute architecture group the best way to organize, model, define attributes.
Attribute discussion is orthogonal to the query definition.
No implication that only these attributes could be used with this query. Some features of this query type could be used with existing systems. Separate out the attribute set from the RLQ query. Maybe yes, and maybe no. There are some underlying difficulties with this assumption.