Subject: Re: best server option

From: James Kempf <[email-masked]>
Date: Thu, 6 Jul 2000 09:59:17 -0700 (PDT)

Erik,

>
>BEST SERVER SEARCH EXTENSION
>
>This extension is used with a SrvRqst or SrvRply.
>
>When used with a SrvRqst, either Mode = 1 or Mode = 2.  The Criteria-
>Attribute-Tag to use is specified.
>
>When used with a SrvRply, Mode = 4 and the Criteria-Attribute-Tag
>is returned.  If no Best Server Search Extension is present in the
>reply, then a reply of one service means there *is only one service.*
>If the Best Server Search Extension is present, then one service
>means the 'best' one was returned.
>
>      0                   1                   2                   3
>      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>     |      Extension ID = TBD       |     Next Extension Offset     |
>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>     | Offset, contd.|     Mode      | Criteria-Attribute-Tag Length |    
>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>     |                    Criteria-Attribute-Tag                     /
>     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>Mode = 1 means MINIMUM
>       2 means MAXIMUM
>       4 means BEST
>
>The Criteria-Attribute-Tag is an attribute tag, which is an attribute
>of services advertised with the service type present in the SrvRqst
>message.
>  
>

This looks fine, but I think there needs to additionally be some way
to define what a best means, sort of like a service type template
defines what the service itself means. This allows designers of
services to communicate their intention to designers of clients
that use the services.

Perhaps it could be an extension to the service type template.

		jak

---

From: Erik Guttman <[email-masked]>
Date: Thu, 6 Jul 2000 19:15:29 +0200 (MET DST)

> Perhaps it could be an extension to the service type template.

That's a really cool idea!  

In that case you could send a 'BEST' mode extension in the request to 
an SA (with no criteria attribute) and it would know what to do based 
on the service type.  

It wouldn't work to count on the DA would know how to compute service
specific 'best' services, however.  The DA has to handle any service
as a generic 'directory.'  SAs on the other hand could be customized
to deal with specific service types.

Erik