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
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