requirements - 4-corner wording

Based on yesterday's discussion I drafted a requirement for 4-corner
support. How is this:

"XKMS MUST be usable in a 4-corner application model. Specifically, an XKMS
server should be able to pass requests to another XKMS server for processing
without excessive overhead. Although the definition of server chaining and
referral mechanisms are out of scope for the first XKMS
requirements, such mechanisms should not be precluded by the XKMS protocol
or processing specifications"

Also for a definition of 4-corner in the definitions section:

4-corner model
A model where clients interact with a single point of contact, such as a
local bank for example, submitting requests and obtaining responses. This
point of contact may interact through a backend mechanism with the point of
contact for another participant in the system, enabling a consistent and
simple interface for interactions across a large system population. For more
information see the Identrus documentation (http://www.identrus.com/").

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Frederick Hirsch
Zolera Systems, http://www.zolera.com/
Information Integrity, XML Security