Issue 238 proposal v2

[Anish Karmarkar <Anish.Karmarkar@oracle.com>]

I have uploaded v2 of the 238 proposal at:

http://www.oasis-open.org/apps/org/workgroup/sca-assembly/download.php/40315/sca-assembly-1.2-spec-wd01-issue238v2.pdf
and
http://www.oasis-open.org/apps/org/workgroup/sca-assembly/download.php/40314/sca-assembly-1.2-spec-wd01-issue238v2.doc

If you don't want to be confused with spurious diffs from crossref 
updates please look at the PDF and not the Word doc. The PDF version 
contains pages only from sections 8, 9 and Appendix A. These three 
sections are the only ones that are relevant to the proposal.


If you are curious as to where the other spurious changes in v1 came from:
All of them are from cross-reference updates. 4 of those occurred 
because they used the wrong cross-reference (a cut-and-paste error that 
is also present in WD01). I fixed those 4 cases. The other cases, I 
tried to fix them, but Word keeps updating the auto-generated 
cross-reference text (with identical text) even after I accept the new 
changes -- I can't figure out why Word keeps doing that. I tried using 
OOo, but that made the problem even worse. The diffs showing up in the 
example Snippet references weren't worth fixing, since 1.2-wd01 is a 
branch of 1.1-cd04 and at some point we'll have to migrate to 1.1-cd06 
(or later).

In any case, till we migrate to the latest version of 1.2, the best 
solution for now I think is to look at sections 8/9 and Appendix A as 
those are the only sections relevant to this proposal.


Here is the explanation for the proposal (the actual text changes are 
small, but below is the rationale for those changes):

There are three syntactic uses of eventType (or some various of it):
(a) in the EDL, (b) in the event instance/message, (c) in the filter

(a) The EDL defines a QName for the event type and points to the 
associated XSD. If you are not using XSD, there will some other way to 
define the event type (the example that has been discussed in the past 
is a fully qualified Java class name). This is the EDL eventtype. In the 
proposal it is called sca:eventTypeXSD. If we use the EDL defined by W3C 
WS-RA then we won't be doing any work wrt this.

b) the event instance *may* contain metadata for event type (such as a 
header). For example, there may be a eventType header. Note the spec is 
silent on this.

c) The filters on a consumer/channel may specify an filter based on 
event types. This is the one thing that is specified by our spec and 
will persist even if we adopt WSRA's EDL. The filter schema consists of 
two parts:

eventType -- an abstract element (substitution group head)
eventType.sca -- concrete element that uses our EDL (or will point to 
WSRA's EDL, if adopted) and is part of the substitution group. This 
requires that the definition of the event type must use XML schema as 
defined by our spec (currently) or WS-RA, if adopted.

One can extend this by creating eventType.java or 
eventType.myFavoriteExtension

It is important to note that the eventTypeXSD syntactic element defined 
by the EDL (in (a) above), cannot be used for filtering. The filtering 
element points to one or more QNames/namespaces used by the EDL. The 
structure of the elements is very different. This is the main error 
pointed out by issue 238 wrt 1.2-wd01 that this proposal fixes.

An example:

(a) EDL --

<eventDefinitions targetNamespace="http://example.org/edl"; ...>
   <eventTypeXSD name="PrinterEvent" element="foo:PrinterData"/>
</eventDefinitions>

(b) Event instance, if it used XML (made up example) --

<foo:PrinterData ...>
   <foo:header>
     <foo:eventType>...</foo:eventType>
     ...
   </foo:header>
   <foo:body>
     ...
   </foo:body>
</foo:PrinterData>

(c) filter on the event type PrinterEvent defined by the EDL above --

<filters xmlns:ex="http://example.org/edl"; ...>
   <eventType.sca qnames="ex:PrinterEvent" />
</filters>


-Anish
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