Hi Wendy, Very interesting proof-style argument!
I will rephrase your statement slightly and let's see if I understand it correctly. Let ird be the uri of the IRD that a client c discovers. Let o_ird be the object content that the client c fetches when retrieving the URI ird. Assume that o_ird contains at least two resource IDs (at the same domain or not) whose media-type is networkmap. Then the client c encounters a complexity of choosing among multiple network maps. Before we solve the problem by naming or assigning attributes to network maps, let's try to get some sense on the cases that a network provides multiple network maps. Consider two given network maps nm1 and nm2. There are two types of relationship between them: 1. They are independent, e.g., nm1 maps access technology; nm2 maps geolocation; 2. They are related. In particular, we can define a refinement relationship, i.e., nm2 is a refinement of nm1, iff for any pid2 in nm2, all IP addresses in pid2 belongs to only one pid in nm1. In the current ALTO spec, there is no syntax to define the second case, although there were discussions in early days on defining one pid based on another pid (e.g., first define ASN and then use ASN). Note that a client can discover refinement by fetching two network maps and conducting a test as in the definition, although this can be expensive. Now, consider the set of network maps contained in o_ird. Build a graph where each node is a network map in o_ird. Some of them are related by the refinement relation. If nm2 is a refinement of nm1, we draw an edge from the node representing nm1 to that representing nm2. If this graph has a single root, then it is natural to label the root as the "default" or "root". If it has multiple roots, then I assume that one of the roots is likely labeled as default, but the semantics is less clear. Richard On Tuesday, July 23, 2013, Wendy Roome wrote: > Here's why an IRD returned by ALTO discovery must must have a default > network map. Consider an ALTO client that gets the server URI via > discovery. By definition, a discovery client must be provider-independent. > Because resource ID names are provider-specific, a discovery client cannot > be pre-configured with a map ID. Hence any IRD returned by discovery MUST > mark one of its maps as the default. If not, a discovery client can't > decide which network map to use. > > Of course, there'd be no problem if ALTO discovery could return a map ID > as well as a URI. But I gather that's not possible. > > - Wendy Roome > > > From: "Y. Richard Yang" <[email protected] <javascript:_e({}, 'cvml', > '[email protected]');>> > Date: Tue, July 23, 2013 13:10 > Subject: Re: [alto] Clarifying Cost Map Dependencies on a Network Map > > This does imply that any ALTO server returned by the discovery protocol >> must provide default-network-map. >> >> > Not sure I understand why must return a default-network-map? >
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