Meeting Summary 18 February
The meeting this week focussed on one topic - how to apply POWDER where there is no structure in a Web site's URIs that can be used to create meaningful URISets.
POWDER is about creating sets of URIs and then describing them - those sets being defined by the host, path components etc. But there are cases where this isn't possible and all one can say is something like 'example.org contains some resources that are blue and some resources that are red.' The danger is in creating two statements that conflict, i.e. 'all resources on example.org are blue' AND 'all resources are red.' After much discussion, it was provisionally agreed that the way around this would be to allow POWDER documents - that is, XML files with a root element in the POWDER namespace that contain an attribution element - not to contain any DRs at all. Rather they can contain simply descriptors elements that are not part of any DR and therefore have no scope.
The attribution element MAY however include an aboutHosts element, the value of which is a white space separated list of hosts. If such an element is included, then the data in the document, whether in DRs or just descriptions, can only be applied to resources available from those hosts. Such a POWDER document provides some discovery information - example.org contains both red and blue resources - but does not provide any further information about where on that host those resources are. One would need to look at the resource (or perhaps the HTTP headers) to note a link pointing to a particular description.
It's not ideal but a) it does not break the POWDER model; b) it does not lead to the creation of conflicting DRs; c) the expressivity is limited by the (lack of) URI structure across the described resources, not by the design of POWDER.