Hi Alistair, > I'm new to sword and this thread, so apologies if this has already been > covered, but one thought... > > On Fri, Feb 04, 2011 at 08:54:49AM +0000, Richard Jones wrote: >> Dear All, >> >> Thanks for your extensive feedback on the various issues that we have >> been discussing on this list, it has been really valuable for the >> project team to get this input. We have, we think, identified 3 >> particular issues of contention: >> >> 1/ Whether the Statement should be embedded in the Deposit Receipt or be >> a separate document referenced in an atom:link element > > ...why don't you allow servers to optionally inline the content within the > link? There are two separate IETF I-Ds covering an atom link inline extension, > one older [1] and one newer [2] which I believe is active. > > I.e., allow something like... > > <atom:entry> > <atom:link rel="http://purl.org/net/sword/terms/statement"; > type="application/rdf+xml" href="http://.....";> > <atom:inline> > <rdf:RDF> > <!-- ORE statement goes here --> > </rdf:RDF> > </atom:inline> > </atom:link> > <atom:link rel="http://purl.org/net/sword/terms/statement"; > type="application/atom+xml;type=feed" href="http://.....";> > <atom:inline> > <atom:feed> > <!-- statement goes here --> > </atom:feed> > </atom:inline> > </atom:link> > </atom:entry> > > Seems to be a fairly commonly used pattern (we use it heavily for a malaria > data repository project).
This is quite intriguing, I definitely want to consider using this approach. There is only one thing that I'm not sure about: It is possible (at the moment) that servers may only supply the embedded Statement, and not any atom:link elements which resolve to it. In this case there would be no atom:link to embed the atom:inline inside. The question then, is should we /require/ that a server be able to provide at least one separate Statement URI? If so, then I think we should adopt the atom:inline approach here, but if not we'll have to continue with the rdf embedded as foreign markup. Looking at the examples in the references, I see that they actually embed atom:feed elements; this would level the playing field nicely with ORE as the embedded format. Thoughts? Cheers, Richard > > Cheers, > > Alistair > > [1] http://tools.ietf.org/html/draft-mehta-atom-inline-01 > [2] http://tools.ietf.org/html/draft-snell-atompub-inline-01 > >> >> 2/ Whether to use OAI-ORE for the Statement format or an Atom Feed (as >> per CMIS and GData) >> >> 3/ How the client and server should negotiate over the format of the >> content returned by the edit-media link (EM-URI) >> >> The project team has gone through each of these issues carefully, and >> attempted to extract the simplest solutions but with a view to keeping >> the SWORD 2.0 specification quite open at this stage, so that community >> best practices can actually inform the standard itself in the long run. >> Therefore, we're proposing the following approaches to these issues: >> >> 1/ Whether the Statement should be embedded in the Deposit Receipt or be >> a separate document referenced in an atom:link element >> >> If the Statement is to be embedded in the Deposit Receipt, then it needs >> really to be in OAI-ORE form, for the purposes of being clear foreign >> markup. Nonetheless, bearing in mind that there is a question as to >> whether the Statement should be an Atom Feed, it is clear that this >> solution will not be adequate by itself. We therefore propose that the >> standard provided to the project's funded developers to code against >> says that an OAI-ORE serialisation MAY be embedded in the Deposit >> Receipt (the Deposit Receipt will not be required to meet the OAI-ORE >> spec for being a resource map itself). >> >> Alongside - or instead - of this, there MAY be one or more atom:link >> elements in the Deposit Receipt which link to an external Statement. >> These atom:link elements can specify their type attribute to say whether >> they are an application/rdf+xml or application/atom+xml;type=feed. It >> will be a requirement of the spec that there MUST be an embedded >> Statement or at least one separate Statement. >> >> Therefore, you may see a Deposit Receipt like: >> >> <atom:entry> >> <atom:link rel="http://purl.org/net/sword/terms/statement"; >> type="application/rdf+xml" href="http://....."/> >> >> <rdf:RDF> >> <!-- ORE statement goes here --> >> </rdf:RDF> >> </atom:entry> >> >> 2/ Whether to use OAI-ORE for the Statement format or an Atom Feed (as >> per CMIS and GData) >> >> Another good reason for the approach in (1) is that this means we can >> provide different Statement URIs with different type attributes. We >> plan to ask developers to produce an ORE and an Atom Feed Statement >> format under the project funding. So you may see a Deposit Receipt like: >> >> <atom:entry> >> <atom:link rel="http://purl.org/net/sword/terms/statement"; >> type="application/rdf+xml" href="http://....."/> >> >> <atom:link rel="http://purl.org/net/sword/terms/statement"; >> type="application/atom+xml;type=feed" >> href="http://....."/> >> >> <rdf:RDF> >> <!-- ORE statement goes here --> >> </rdf:RDF> >> </atom:entry> >> >> The combination of approaches in (1) and (2) may seem woolly or >> indecisive, but we believe that we can't determine in advance which of >> these approaches is better, and that it should be up to the community of >> users and implementers to decide which approach works best based on >> actual usage of the developed software. Therefore, while the burden of >> implementation is placed on the funded portion of the project, we expect >> community driven implementations/usages to favour one approach over >> another (possibly taking into account things like compatibility with >> GData and CMIS, or preferring the more semantic web approach of ORE). >> We can then use this information later in deriving a SWORD spec which is >> based on best practices. >> >> 3/ How the client and server should negotiate over the format of the >> content returned by the edit-media link (EM-URI) >> >> The Content Negotiation issue arises from the fact that AtomPub requires >> at most one edit-media URI with a given type to be available in the Atom >> Entry (Deposit Receipt). Since the SWORD server may contain multiple >> files rather than the one file that AtomPub assumes, what this EM-URI >> returns under GET is unclear. We initially considered 2 approaches: >> >> a/ A separate HTTP header like Accept-Packaging to allow content >> negotiation on a package format >> b/ A separate HTTP header like Accept-Media-Features to allow general >> content negotaiton on feature sets >> >> As we discussed, both of these have pros and cons, and none of the >> approaches to doing this are marked by any best practices, which makes >> the project team unwilling to commit to anything too complex or >> substantial, at a risk to the simplicity and overall success of SWORD. >> Instead we are suggesting adopting a much simpler approach: >> >> The Deposit Receipt can contain already contain a sword:package element >> (as per SWORD 1.3), and SWORD 2 plans to allow an arbitrary number of >> such elements. These elements will describe the packaging formats >> supported by the server, so the client will know in advance what the >> capabilities of the server are. Therefore, instead of engaging in a >> content negotiation process, the client will just specify a separate >> HTTP header indicating what package format should be returned. Whether >> this header re-uses the Packaging header used during deposit or >> specifies a new header has yet to be decided. >> >> >> Hopefully these approaches make sense to the group. We are interested >> in how you think these will go down both during the project and beyond >> in the community, and if there are any obvious problems with what we're >> proposing here as the way forward for SWORD. >> >> All the best, >> >> Richard >> (On-Behalf-Of the SWORD project team) >> >> >> >> ------------------------------------------------------------------------------ >> The modern datacenter depends on network connectivity to access resources >> and provide services. 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