> How can you have a generic XSLT client as described which will
> interoperate with all SRU servers, if the echoed XCQL were optional?
You can't, it would be the choice of the implementor/database owner to
make the target available for that type of client. In fact it might be
desirable to exclude webb-browsers since few servers could stand the
load of being Slashdotted.

/M