W3C home > Mailing lists > Public > xmlschema-dev@w3.org > August 2012

Re: XML Schema quiz on default values

From: C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
Date: Fri, 24 Aug 2012 10:45:20 -0600
Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, xmlschema-dev@w3.org
Message-Id: <2A13AC8C-712E-4465-8E36-8208A393DA46@blackmesatech.com>
To: Daniel Dui <daniel.dui@gmail.com>

On Aug 24, 2012, at 10:16 AM, Daniel Dui wrote:

> My experience is that a user that sees the default feature in XML schema expects that the default value is the value that an optional element "takes" when it's not included in the instance document.
> You might think it's naive, but that's the reality for many C++/Java/C# developers who need to deal with XML from time to time. It's not, I hope, for XML specialists.
> The biggest issue that I have found with default values, and why I usually end up not using them, is that the default value is specified only in the schema and not in an instance document. So a consumer app that processes the document in a schema-unaware fashion has no knowledge of the default value..
> Usually I work with in organisation that want to build schema-aware producers and schema-unaware consumers. If the consumer can't use the default value, why specify it in the schema?
> Another scenario is when there are multiple consumers, some schema-aware and some schema-unaware. Using default values can introduce inconsistent behavior across different consumers within the same organisations.

Thank you; that's helpful.

* C. M. Sperberg-McQueen, Black Mesa Technologies LLC
* http://www.blackmesatech.com 
* http://cmsmcq.com/mib                 
* http://balisage.net
Received on Friday, 24 August 2012 16:46:06 UTC

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