Re: Postscript on Today's DQL Discussion

From: pat hayes (
Date: 06/27/02

  • Next message: Richard Fikes: "Re: Postscript on Today's DQL Discussion"
    Richard, on going through your document with a fine comb, Ive a few 
    more niggling questions/suggestions, which Ill summarize here in case 
    you (or anyone) wants to jump on them.
    It may not be practical for every answer to specify the answer KB 
    used to generate it. For many servers this information may be 
    proprietary, in any case. So I don't think we should require this. 
    However, that raises a new question: should we allow a *query* to say 
    that it will only accept answers with an answer KB specified? I think 
    that would be good.
    One general way to handle this would be have the query contain a 'KB 
    specification' which could be either a list of urirefs (KB names) or 
    one of the three kinds of variable. A must-bind variable means, I 
    must know the answer KB. A no-bind means I don't care. Bindings to 
    these variables are allowed to be arbitrary lists of urirefs, to 
    allow for the case where the server uses a lot of KBs in its answer. 
    Then Yahoo (say) can just refuse to accept queries with a must-bind 
    KB spec, for example.
    Another, related, question. Suppose the query specifies the answer KB 
    to be used, but the server simply doesn't know the KB uriref? It 
    could just hand back 'unknown', but it would be more informative to 
    allow a new kind of token, maybe 'unknown-KB'. In general, we should 
    write the spec so that things like the set of tokens can be extended 
    in future, in any case, right?
    A question about 'none'. Do we want this to mean that there are no 
    other answers entailed by the KB, or that there are no other answers 
    *which fit the specifications of the query* that are entailed, or 
    that there are no other answers *of the kind that this server knows 
    how to reason about* that are entailed....? Or maybe something else? 
    I guess I am suspicious about it being possible for most servers to 
    be absolutely certain that there are no other entailed answers *at 
    all*.  At any rate, we need to be painfully exact about what we do 
    mean, and Im not sure that just saying 'no further answers are 
    entailed' is exactly what we intend here (?).
    Since we don't say what a justification is, and since there isnt 
    (yet) any defined notion of 'proof' in DAML, why not just omit this, 
    and just say that an answer might contain other stuff to be defined 
    in future, and a query might contain other stuff which is relevant to 
    said other stuff in the answer (???)
    Should we allow a query to specify any (lower or upper) bounds of the 
    number of answers it wants per answer bundle? An upper bound seems 
    like it might be useful.
    Finally, do we want to allow the case where a query premis is 
    specified, but no other KB is allowed to be used? If so, how does the 
    query specify that?
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