> Why shouldn't this be allowed?

For reasons outline that this leads to queries involving serverChoice
which cannot be performed by explicitly requesting indexes.

<snip>

> If you don't know what 
> you want, you
> leave it out, and the server supplies a default value.

That is also the case with i and iv and isn't the issue I have with case
ii,iii,v and vi.

It isn't the default value that is at issue, it is that the default
value in cases ii,iii,v and vi are values which would not normally be
allowed in CQL queries sent to that server.

To take your example
 
> If I don't supply recordSchema, and ask for 1 record, the 
> server should be
> able to respond with a full record (eg EAD or METS or MODS).  
> On the other
> hand if I ask for 50 records, then the server should be able 
> to respond
> with a brief record (eg simple dublin core)

The recordSchema analogue of the cases I outlined in ii, iii, v and vi
would be if in your example, the server would *only* return simple
dublin core in the case quoted in your example (i.e. if the client does
not specify a recordSchema and requests more that one record). A client
which wanted simple dublin core would not be able to explicitly request
it.

My view would be that if a server returns simple Dublin Core when the
recordSchema is omitted by the client, then I don't see why the client
can't explicitly request that record schema and expect to get it.
Similarly if the server uses a particular index when
omitted/serverChoice I don't see why the client can't explicitly ask for
for that index in a query. In fact cases ii and iii can easily be turned
into case i by adding the index used by serverChoice to the profile
(e.g. Ralph would add ralph.BasicIndex to the list of supported
indexes).

>If all I want to do is have a trivial
>Google like interface (eg the server -only- accepts serverChoice) then
why
>shouldn't I?

The case when a server *only* supports serverChoice is possibly an
exceptional case although there would be no hardship in this server
supporting a google.freetext (or adlib.anywhere) index (with omission
and serverChoice defaulting to that on the basis that there isn't any
other index for them to default to).

Matthew