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Subject: RE: [election-services] Language Binding Generators

OK - but this still does not answer my basic observation.
So we rename everything EML110ElectionEvent, EML120, EML130 etc.
Everyone builds their V6 language bindings.  Then along comes V7 of EML and guess what - everything is still called EML110ElectionEvent, EML120, EML130 etc - so we're back to square one - the language binding tools still get confused because more than one thing is called the same name (remember they can encounter both V6 and V7 XML instances potentially in the same election from different devices.
And we already have the notion of a single unified parser - handling top level EML and then determining from the Id which content type they are parsing.  I know on my last project we built this for XMLBeans without needing any additional schema devices.
Fundamentally I'm not convinced we're buying anything here.  I'd be the first to jump on needing to make things easier - but right now I'm not seeing any.  The binding tools like XMLBeans are fully capable of handling this - and by making software developers right up front deal with this issue in their implementations - we're actually helping them build correctly and ensure their software is version enabled.
I prefer the simple and clear - and if people want to build supporting additional schema for language bindings - they can do that - I just don't see that is our job.  Also - remember - any new schema has to be documented - and reviewed thru the OASIS process - and I'm not sure a schema purely to help language binding is something we're going to be able to justify.
Thanks, DW


-------- Original Message --------
Subject: RE: [election-services] Language Binding Generators
From: Richard J Cardone <richcar@us.ibm.com>
Date: Sat, January 24, 2009 2:05 pm
To: "EML TC" <election-services@lists.oasis-open.org>


The 4 points below are responses to the 4 corresponding points in your last posting.

1) I agree that EML schema numbering is valuable and intrinsic to the architecture; I don't suggest that we change it at all.  I only propose that we change the top-level <EML> element name in schemas so that each type of EML document begins with a unique and descriptive element.  The schema file names don't change.  For example, the 110-electionevent-v5-0.xsd file would be modified so that the top-level definition <xs:element name="EML"> would now read <xs:element name="EML110ElectionEvent"> (or something similar).  In my 1/22 posting, I suggest that this approach clarifies EML semantics as well as increases the convenience of using language binding generators with EML.    

While we are on the subject, we might also consider a new v6 schema that would leverage the proposed top-level element name changes.  This new schema would define a unique top-level element for all EML documents.  This new top-level element, however, differs from the current <EML> definition because it is uniquely defined in exactly one schema file.  For the sake of discussion, I'll call this new schema 001-emldocument-v6-0.xsd with a top-level element named <EMLDocument> and defined it as follows:

        <xs:element name="EML001Document">
                                <xs:element ref="EML110ElectionEvent" />
                                <xs:element ref="EML120Interdbt" />
                                <xs:element ref="EML130Response" />

Using the above definition, every EML document would start with an <EML001Document> element and then contain content that conforms to exactly one of the other EML schemas.  The nice thing about this design pattern is that language binding generators would be able to generate a single parser that could parse any valid EML content, which brings us to my next response.

2) I agree completely, specifications should be written independent of any particular tool.  Language binding generators, however, are a well-established class of tools for working with XML schemas and we should at least avoid making it difficult to use those tools with EML.  The last time I checked there were dozens of such generators available.

3) Versioning is challenging and applications that use statically generated parsers have to be especially sensitive to the situation.  On the other hand, we want to give developers the greatest latitude in choosing an XML parsing technology that suits their applications.

4) As far as documentation changes go, the EML-Process-Data-Requirements-v5.0 document doesn't seem to reference the top-level <EML> element at all; the EML-Schema-Descriptions-v5.0 document also does not reference the <EML> tag, though I may have missed where it's mentioned; and the EML-Data-Dictionary-5.0 document would have to be extended to include the 28 or so new top-level element names.  As far as how much change is too much change for v6, that sounds like a topic for another discussion!      


"David RR Webber \(XML\)" <david@drrw.info>
01/23/2009 10:22 AM
Richard J Cardone/Watson/IBM@IBMUS
"EML TC" <election-services@lists.oasis-open.org>
RE: [election-services] Language Binding Generators

That's one way of looking at it the counter position goes something like this:
1) Having a set of schemas numbered by group and function is a powerful plus in the way EML is architected and organized - I know what the 100, 200, 300, 400, 500 and 600 series do.
2) XMLBeans is just a tool - normally we do not make specification changes to accommodate tools - that sets an ugly precedent.
3) Versioning is a challenge for static content handlers like XMLBeans that generates fixed memory structures.  Obviously the dynamic XSLT style *any* handler approach is more flexible.  So - whether I call a root element something like EML, or VotingRecords or Foobar - XMLBeans will still have an issue when it comes to V7 release - since that will be using those same root element names so now that will be conflicting.  It does have ways to overcome this - and we should simply refer developers to those - the folks over on the XMLBeans dev list will be happy to explain (BTW - I'm on the XMLBeans dev list!).
4) Making this change would have extreme knock-on ramifications for the documentation and associated details that will add considerably to the effort need to produce the EML V6 voting package for OASIS.  Not only that - but the same thing for people who have implemented V4 and V5 already - code wise.
Thanks, DW

-------- Original Message --------
Subject: RE: [election-services] Language Binding Generators
From: Richard J Cardone <richcar@us.ibm.com>
Date: Thu, January 22, 2009 1:16 am
To: "EML TC" <election-services@lists.oasis-open.org>


I don't remember exactly how customized name mapping is done in Xmlbeans, but I think it involves the use of a poorly documented configuration file.  I also believe JAXB provides a way to specify non-default class name mappings, but again I try to avoid these complications whenever possible.  The v6 effort offers us an opportunity to make EML schemas generally easier to use with code generators.  My argument for considering at this time a change to the top level element names in EML schemas goes like this:

1. The top level element in an XML document should reflect the contents of that document.  For example, it's reasonable for the top level element in a purchase order document to be <PurchaseOrder>.  Likewise, it's reasonable for the top level element in an EML ballots document to be <EMLBallots> (or something similar).  In a sense, it's misleading that dozens of different documents start with the <EML> element even though their content and use are unrelated.  

2. The use of language binding generators is simplified when different schemas define different top level elements.  These generators are valuable because they remove much of the drudgery and pitfalls of parsing, reading, and writing complex XML documents, especially when compared to technologies like SAX and DOM.  By using different top level element names, generators can use their default name mapping algorithms without causing name conflicts.  Using the default name mapping reduces the burden on developers and generally simplifies applications.  Also, different generators are going to have different levels of support for name customization and it would be nice to avoid the whole issue.  

3. If the installed base of EML 5.0 isn't prohibitively large, then breaking upward compatibility to EML 6.0 by renaming top level elements to be more descriptive may be worth it.  If we don't do it now, it probably will never get done.  I don't know if any other v6 change breaks upward compatibility (i.e., requires code changes in applications that use EML 5.0), but the level of near-term disruption needs to be weighed against long-term payoff.


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