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Re: Conditional Levels of a Schema

From: Pete Cordell <petexmldev@codalogic.com>
Date: Mon, 6 Apr 2009 11:31:10 +0100
Message-ID: <762CDF807D4C40D5BE128AF27D4704B1@Codalogic>
To: "Michael Kay" <mike@saxonica.com>, "'Dieter Menne'" <dieter.menne@menne-biomed.de>, <xmlschema-dev@w3.org>
I don't know whether this is possible, but could you define an attribute in
another namespace, such that you do:

<xs:element name="patients" minOccurs="0" maxOccurs="1"

and then have a style sheet that says if @hrm:context-specific is present,
modify the minOccurs and maxOccurs attributes appropriately for the mode you

One benefit is that the base schema is still a valid schema and hence might
be easier to work with.  It appears to self-document quite well also.


Pete Cordell
Codalogic Ltd
Interface XML to C++ the easy way using XML C++
data binding to convert XSD schemas to C++ classes.
Visit http://codalogic.com/lmx/ for more info

----- Original Message ----- 
From: "Michael Kay" <mike@saxonica.com>
To: "'Dieter Menne'" <dieter.menne@menne-biomed.de>; <xmlschema-dev@w3.org>
Sent: Monday, April 06, 2009 11:04 AM
Subject: RE: Conditional Levels of a Schema

> This is a common requirement, and there's no simple answer to it.
> One approach is to define restricted types: in your more general schema,
> the
> item is defined as optional, and then you have types derived by
> restriction
> than make it mandatory or prohibited. The instance document then has to
> indicate which version of the type it wants to use by use of xsi:type; or
> alternatively, if you schema validator allows it, you can indicate which
> top-level type you want to validate the message against through your
> validator's API.
> There are a number of difficulties with this approach; one is that you not
> only have to define restricted types for the element whose content model
> is
> directly affected, but for its ancestor elements all the way up to the
> top-level message structure. Because restrictions are defined by repeating
> the content model rather than simply stating the differences, this can be
> a
> maintenance nightmare.
> One approach I have used in the past is to generate the schema documents
> defining these restricted types automatically (using XSLT). This reduces
> the
> maintenance burden - but in-house tools like this have their own problems
> in
> terms of maintenance and documentation.
> Probably a simpler approach, and one that is closer to your description of
> the problem, is to implement the conditional logic not by generating
> subtypes but simply by modifying the main type definition. Again you can
> do
> this using XSLT: just define a stylesheet where the schema document is the
> body of the <xsl:template match="/"> template rule, and it can then
> contain
> things like <xs:element name="patients" minOccurs="{$param}"/> where
> $param
> is a stylesheet parameter. One disadvantage of this approach is that
> different variants of the schema cannot coexist in the same application -
> typically your schema cache will only allow one version of a type with a
> given name.
> XSD 1.1 allows you to supplement the grammar constraints with assertions,
> so
> for example the message in which the <patients> element is probited could
> be
> defined using <xs:assert test="empty(//patients)"/>. You could also use
> conditional type assignment at the message level to select the type for
> validation based on a user-defined attribute such as @message-type. These
> facilities are implemented in Saxon-SA 9.1 which you could use to explore
> the concept.
> Michael Kay
> http://www.saxonica.com/
>> -----Original Message-----
>> From: xmlschema-dev-request@w3.org
>> [mailto:xmlschema-dev-request@w3.org] On Behalf Of Dieter Menne
>> Sent: 02 April 2009 19:06
>> To: xmlschema-dev@w3.org
>> Subject: Conditional Levels of a Schema
>> Hi,
>> we are currently defining a format for medical data storage
>> (hrmconsensus.org). The full version is available
>> http://hrmconsensus.org/media/hrm/xhrm/xhrm02/xhrm0_2.xsd here .
>> In the simplified example below, we have the always mandatory
>> deviceTyp. For patientsType, we would like to have a global
>> conditional switch so that three flavors are possible
>> -- minOccurs = "0" for internal clinical use
>> -- minOccurs = "1" for archiving, must contain patient info
>> -- minOccurs = "never" anonymized, must not contain patient info
>> I know that the latter is not possible, that conditionals are
>> not supported in XSL, and that Schematron would be an
>> alternative.  Note that the conditionals occur in several
>> nesting levels, so that we cannot easily combine versions of
>> a master element with details, but they are always of the
>> type "may", "must", "must not".
>> We would like to avoid having several xsd files and prefer a
>> common file with branching. Any ideas or references to ideas
>> are appreciated.
>> Dieter Menne
>> on behalf of the hrmconsensus group.
>> <?xml version="1.0" encoding="utf-8"?>
>> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" version="0.2">
>> <xs:element name="xhrm">
>> <xs:complexType>
>> <xs:sequence>
>> <xs:element name="device"
>> type="deviceType"/>
>> <xs:element name="patients"
>> type="patientsType" minOccurs="0"/>
>> </xs:sequence>
>> </xs:complexType>
>> </xs:element>
>> </xs:schema>
>> -- 
>> View this message in context:
>> http://www.nabble.com/Conditional-Levels-of-a-Schema-tp2284233
> 4p22842334.html
>> Sent from the w3.org - xmlschema-dev mailing list archive at
>> Nabble.com.
Received on Monday, 6 April 2009 10:32:01 UTC

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