Re: (DQL) Servers and Clients

From: Pat Hayes (
Date: 11/29/01

>I am composing responses to the recent e-mail messages regarding DQL and
>am planning on sending out a series of such messages.  Here is a simple
>one to get started.
>I proposed referring to the agent sending the query as the "client" and
>the agent receiving the query as the "server".
>Pat said:
>>  BTW, I really
>>  dislike that term 'server'; it suggests an asymmetry between the
>>  querier and queried that isn't likely to survive in the broader SW
>>  world, I think.
>For me, it was simply a matter of convenience to refer to the "query
>answering agent" as the "server" and to the "query asking agent" as the
>"client".  Some such shorthand names are useful, and those terms are the
>ones typically used regarding knowledge servers and data servers.  I
>don't care much what names we use, although "querier" and "queried"
>don't seem to me to be improvements.

I would agree with you there, to be sure; I didn't mean to suggest 
that as an alternative terminology. My concern was just a worry that 
this usage is going to be used in a sense which suggests that clients 
and servers are different *kinds* of agents, which would be a pity. 
For example, consider a situation (which is likely to arise very 
soon, if not already) where a simple query/answer protocol goes on 
between a Kbase A and an agent B, but where B's role is to act as a 
query-handler for a more sophisticated kind of query coming from C, 
eg where C is asking about things like the numbers of answers, which 
B is compiling into a process of simple queries and responses.  What 
is B here? In the B/C exchange, it is a server; in the A/B exchange, 
it is a client. If we use these terms as *classifications* (which 
their traditional usage would suggest), then the role of 
intermediaries like B becomes cloudy. Whereas I think that agents 
like B are likely to have a very important and central role in 
web-based query services; and in fact that our own discussions on 
this list suggest this possibility already.

So, in a word, as long as we are clear that something can be a client 
from one perspective but a server from another, and there is nothing 
paradoxical or mysterious about this, then fine.


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