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Subject: Re: [ubl] Extension element children
Good to hear from you John. I was probably lax in my phrasing - I meant the extension would be * displaced * (not replaced) as last element when the document is extended in any minor version. In other words, as Mike wrote, the extension element may be last in the document now but, though keeping its position in the sequence, perhaps not stay as the last element in a minor version which extends the document. Glad to hear things in ASN.1 follow so closely the same principles for extension as do those in XSD. This helps the confidence of both being interchangable even when there have been extensions, either through minor versioning (with backwards compatibility, by definition) or through use of the extension element or, hopefully, even with both. In response to Mike (Mike's explanation much clearer than mine) I have some sympathy for the extension element being at the start of the document so its relative position stays the same (and therefore simplifies a rule to say where it should appear). That's if it makes no other difference. All the best Steve On 11/04/06, John Larmouth <j.larmouth@salford.ac.uk> wrote: > I am not sure whether you are talking ASN.1 or something else. > > But for ASN.1, the extension marker can appear anywhere in a SEQUENCE etc, but > if it is in the middle, the syntax is (eg): > > Fred ::= SEQUENCE { > first First, > second Second, > ..., > ..., > third Third, > fourth Fourth} > > The next version puts additional elements between the two extension markers. > > Please note (you probably already know) that if you want backwards > compatability, the extension markers have to be present in "version 1", and you > cannot move them in "version 2". > > John L > > > Stephen Green wrote: > > > Is there any reason why the extension * has * to be at the end of > > the document? The reason I ask is that there may, if so, be an issue > > with further extending the document with minor versions within UBL, > > mightn't there? Such extensions would * have * to be at the end of > > the document - for backwards compatibility. They would therefore > > replace the extension element as the last element in the document. > > I'm hoping the extension element is only placed at the end of the > > document for aesthetic or common practise reasons. > > > > All the best > > > > Steve > > > > --------------------------------------------------------------------- > > To unsubscribe from this mail list, you must leave the OASIS TC that > > generates this mail. You may a link to this group and all your TCs in OASIS > > at: > > https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > > > > > > > > -- > Prof John Larmouth > Larmouth T&PDS Ltd > (Training and Protocol Development Services Ltd) > 1 Blueberry Road > Bowdon j.larmouth@salford.ac.uk > Cheshire WA14 3LS > England > Tel: +44 161 928 1605 Fax: +44 161 928 8069 > > >
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