- From: <noah_mendelsohn@us.ibm.com>
- Date: Fri, 31 Jan 2003 16:52:35 -0500
- To: "Sanjiva Weerawarana" <sanjiva@watson.ibm.com>
- Cc: jones@research.att.com, "Martin Gudgin" <mgudgin@microsoft.com>, xml-dist-app@w3.org
"Martin Gudgin" <mgudgin@microsoft.com> writes: > > We would like to add another DR for discussion. This is essentially a > rewording of my earlier infoset related requirement in concrete form. I > will still be submitting a comment on the abstract feature spec. > > DRXX - A message with all its parts, however separated physically, must > be representable as a single infoset and describable as a single XML > element in an XML schema. I have a concern with this proposed requirement. First of all, I think it is really proposing a change to the SOAP 1.2 Attachment Feature WD [1], and not directly to the implementations for which we are gathering requirements. [1] is fairly clear that attachments are to be named with URIs and accessed using the normal mechanisms of the web (though the actual resolution of the URIs, such as CID:, is presumably provided by the concrete embodiment of the feature in DIME, S+A or whatever.) Furthermore, I prefer the status quo in [1]. I think the sorts of information we are trying to carry are best typed with MIME types; I believe that the URIs that refer to those attachments fit comfortably into the Envelope infoset (as xsd:anyURI elements and/or attributes), but that the resource representations themselves do not. I want to be able to be able to say: "this part is of type image/gif". Indeed, I would propose (I think I did on one of our telcons): DRZZ: It must be possible to associate a MIME type with any or all of the parts in a message. This too, by the way, should perhaps be reflected more clearly in [1], in addition to being reflected in the requirements we are developing for concrete implementations. To restate the position I've stated before: I think we have a pretty good data model for attachments, and it's the Web model not an XML infoset. The XML Infoset is the SOAP envelope. It can, using the usual mechanisms of the Web, make references to resources using URIs. Some of those resources (or representations of them) will be physically packaged with the message, and those we call attachments. In the cases of interest (as opposed to mailto: URIs), the resources should be capable of providing MIME-typed representations of themselves using the normal mechanisms of the Web. So, when the URIs are http: URIs, the resources are (probably) not thought of as attachments and are retrieved using the normal mechanisms of http:. Each particular packaging scheme, as described in [1], defines the means by which it uses some particular set of URIs for retrieval of representations of attachments. That's it. I think it's a reasonable model. I think WSDL can model it. Indeed, I think WSDL needs sooner or later to support this model for non-attachment data. Applying it to attachments is just more metadata, I think (this URI will refer to a resource that travels with the message, this one won't, and this third one could be either way.) I really haven't seen either a motivation or an architecturally strong design for including image/gif data in an XML Infoset. Actually, let me soften that. I think the data model given 2 paras above is the right one for users. If someone wants to do a second packaging that uses the XML Schema hexBinary or base64Binary and that puts the parts in SOAP headers, expanded to character form, I think that might be worth considering. It's not a solution, IMO, to the requirement that we carry binary as binary, which is what we're supposed to do here. I am very much opposed to any proposal that directly or indirectly creates a binary data model in the Infoset at this time. I think it's a very subtle thing to get right, it needs to be very carefully lined up with at least the query data model, it breaks a lot of the things we hold dear about XML as a text standard, and I certainly don't think it's something we should back into in the course of doing attachments. Noah [1] http://www.w3.org/TR/2002/WD-soap12-af-20020814/ ------------------------------------------------------------------ Noah Mendelsohn Voice: 1-617-693-4036 IBM Corporation Fax: 1-617-693-8676 One Rogers Street Cambridge, MA 02142 ------------------------------------------------------------------
Received on Friday, 31 January 2003 16:54:48 UTC