[New-ITS] FW: Version compatibility rules

[Charlie McCay]

Joe
You may be interested in this version compatibility paper, and
discussion of how versioning should be done in the new its -- am digging
out the SPL reference material and will post to the wiki.

Suggest that you join the ITS  SIG list (still called
xml at lists.hl7.org), as the New ITS  work is now an active project within
HL7.org, being hosted by the ITS SIG -- so that list is where the
discussion should be happening now

All the best
Charlie


Charlie McCay, charlie at RamseySystems.co.uk Ramsey Systems Ltd, 23D
Dogpole, Shrewsbury, Shropshire SY1 1ES

tel 01743 232278 / 07808 570172  skype: charliemccay


  

> -----Original Message-----
> From: owner-xml at lists.hl7.org 
> [mailto:owner-xml at lists.hl7.org] On Behalf Of Charlie McCay
> Sent: 24 January 2007 11:58
> To: XML Special Interest Group
> Cc: mnm at lists.hl7.org
> Subject: Version compatibility rules
> 
> All
> 
> The version compatibility rules in HL7v3 are rather brittle 
> (versions change whenever the content model changes, and the 
> element names are not very stable).
> 
> For CDA and HL7 messaging that uses the XML ITS R1, the 
> content model of the instance is determined by the HMD, and 
> only elements in other namespaces may be added (ie any 
> unexpected element or attribute in the
> HL7 namespace will cause an error).  This means that direct 
> forwards and backwards compatibility of the wire format is 
> severely limited.
> 
> The SPL specification introduces a different extensibility 
> method, saying that nodes may be added in the HL7 namespace, 
> but that they should have an attribute to indicate that they 
> are an extension.
> 
> The following is an excellent short article on versioning of 
> languages (and every HL7 specification defines a language) [1].  
> It seems to me that the SPL approach provides the best 
> framework for compatibility, and that we should look at this 
> against David Orchard's paper to improve on XML ITS  R1 for 
> the new ITS work.  It would be interesting to hear from those 
> that are working with SPL as to whether the extensibility 
> rules have proved effective.
> 
> All the best
> Charlie
> 
> [1]
> http://www.xml.com/pub/a/2006/12/20/a-theory-of-compatible-ver
> sions.html
> 
> 
> Charlie McCay, charlie at RamseySystems.co.uk Ramsey Systems 
> Ltd, 23D Dogpole, Shrewsbury, Shropshire SY1 1ES
> 
> tel 01743 232278 / 07808 570172  skype: charliemccay
> 
> 
>  
> 
> 
> ************************************************
> To access the Archives of this or other lists or change your 
> list settings and information, go to: http: //www.hl7.org/listservice
> 
>