Can we mandate the vtag has the equivalent properties of a strong etag in HTTP? i.e. if an alto service is provided by multiple servers then those servers must ensure that vtags are consistent across servers/versions?
If not we could have the equivalent of weak and strong vtags and in the case of weak the client would expect the same server (IP & port) to return consistent vtags but if it connected to another server it would have to re-retrieve the entire cost map if it wanted to compare it to a filtered cost map from the same (2nd) server. (BTW I'm not sure you can compare a filtered costmap against a full cost map if the costs are ordinal) Ben On 15 May 2013, at 17:45, Richard Alimi <[email protected]> wrote: > One question that Wendy brought up was: "if one resource directory can refer > to a different resource directory which may live at a different server or > administrative domain, when is it safe for an ALTO Client to conclude that a > cost metric means the same thing?" A particular example here is the full cost > map and filtered cost map. If the client fetched the full cost map with the > 'routingcost' cost metric, and then later wanted to use a more refined query, > then presumably the client should be able to assume that the values in the > filtered cost map (also with the 'routingcost' cost metric) mean the same > thing. > > A similar thing holds for version tags. If the client finds a cost map with > version tag '1234', under what conditions should it declare that it matches > the version tag for a particular network map? Similar to the cost map > example above, both may come from a different server or administrative domain. > > To resolve this ambiguity, we are proposing to add the following to Section > 8.3.1: > > "The meanings of identifiers used in resources discovered via an entry point > to an ALTO Server (i.e., by the ALTO Discovery Protocol) SHOULD be consistent > with each other. In particular, a particular values for a different cost maps > of the same cost metric should be comparable, and the version tag for a cost > map should be comparable to the version tag for the network map on which it > was based, even if the two maps are provided by a different server." > > I hope the intent here is clear. Admittedly, this is probably not a crisp > enough statement to put in the draft yet, but suggestions on improving it > would be appreciated. > > Thanks, > Rich > _______________________________________________ > alto mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/alto
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