Search on references

[Gary P Cole <Gary.P.Cole@Sun.COM>]

Jeff,

Thank you for offering to explore the possibility that we can support a 
requestor searching based on references.  I don't know whether this will 
help, but I remember some of the issues that surrounded 
search-based-on-references when we discussed this at the Houston BMC 
Face-to-Face. 

One issue was the inelegance of expressing a search condition on 
something that was outside the schema, when elsewhere we used XPath to 
refer to schema-defined elements or attributes.

Another issue was that it might be difficult (or performance-intensive) 
for a provider to combine reference conditions with 
schema-defined-element-or-attribute conditions.  Reference data might be 
managed by the provider separately and stored separately from 
schema-defined data managed by the system or application underlying a 
target.  Combining both types of conditions might require two-stage 
filtering (which might mean that the provider selects a lot of data from 
the target only to discard most of it during second-stage filtering).

In the spec, my approach was to say that
- a requestor may search only based on schema-defined elements or 
attributes, and that
- a provider who wants to support search based on references may expose 
those references as elements or attributes in the target schema. 

The advantages of this approach are 1) that the same search mechanism 
works for both reference and schema-defined data and 2) that the 
provider controls the set of references on which a requestor may search. 

One disadvantage is that this approach defeats one purpose of separating 
references from schema-defined data.  If the provider models a reference 
type in the schema, then a requestor can no longer suppress that 
(reference) data simply by ignoring capability data. Another drawback is 
that the provider might have to "monkey with" a well-known schema in 
order to inject reference elements or attributes.

What are your thoughts on supporting search based on references?

Gary