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Borys MusielakSubject: Mapping complex document with multiple xsd:type's defined
Author: Borys Musielak
Date: 13 Oct 2008 10:00 AM
I have an abstract XSD schema, the real type of document is defined by xsd:type setting for the top-most element. This is also the case for many other elements in the tree.

I'm wondering what is the best way to deal with such schemas in Stylus Studio. Ideally I'd like to be able to define custom mappings for specific xsd:type's.

I'm currently evaluating Stylus Studio to be used company-wise, I do not have any experience with this software, only with pure XSLT. Still, I could not find a straight-forward way of selecting xsd:type for a specific mapping and that's why I'm asking you guys here.

Thanks in advance for any hints.
michuk

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Alberto MassariSubject: Mapping complex document with multiple xsd:type's defined
Author: Alberto Massari
Date: 21 Oct 2008 03:25 AM
Hi Boris,
using xsi:type tends to break the visual mapping metaphor used by XSLT mapper, because the structure is defined by a specific value of an attribute (that can also be different at every occurrence of the same XML element) instead of the element name.
An approach that can work in these cases is to use the XSD as source in the left tree, define one template for each value that xsi:type can use, select it from the combo box at the top of the middle pane, then right click on the schema definition corresponding to the value of the xsi:type and select 'Set as source context' so that all mappings contained inside that subtree will not be influenced by the place where the structure is applied.

Hope this helps,
Alberto

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Borys MusielakSubject: Mapping complex document with multiple xsd:type's defined
Author: Borys Musielak
Date: 23 Oct 2008 04:42 AM
Thanks a lot, Alberto. It would be great if you could point me to some online docs describing this approach in more detail. Especially I'm wondering how to glue those separate mappings together so that they are all part of one complex mapping. Would I need to call the transformations separately, say, from Java code, or is there a more friendly way to do it from within Stylus?

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Alberto MassariSubject: Mapping complex document with multiple xsd:type's defined
Author: Alberto Massari
Date: 23 Oct 2008 09:10 AM
Hi Boris,
this is an example of what I mean: suppose we have this XML document

<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="xsi_type.xsd">
<item xsi:type="box">
<weight>10</weight>
</item>
<item xsi:type="package">
<shape>round</shape>
</item>
</root>

where a single 'item' element is used to represent different type of items, with xsi:type dynamically defining which one has to be used for validation.

The corresponding schema would then be

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:element name="root">
<xsd:complexType>
<xsd:sequence maxOccurs="unbounded">
<xsd:element name="item" type="base"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:complexType name="base" abstract="true"/>
<xsd:complexType name="box">
<xsd:complexContent>
<xsd:extension base="base">
<xsd:sequence>
<xsd:element name="weight" type="xsd:int"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:complexType name="package">
<xsd:complexContent>
<xsd:extension base="base">
<xsd:sequence>
<xsd:element name="shape" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
</xsd:schema>

so that 'item' is pointing to an abstract 'base', and 'box' and 'package' are two concrete types derived by it.
If we modify the schema to say

<xsd:element name="root">
<xsd:complexType>
<xsd:sequence maxOccurs="unbounded">
<xsd:element name="item" type="base"/>
<xsd:element name="dummybox" type="box" minOccurs="0"/>
<xsd:element name="dummypackage" type="package" minOccurs="0"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>

so that XSLT mapper can know all the possible children of the 'root' element, we can do:
- create a new XSLT Stylesheet, without associating it to a source doc
- switch to mapper
- load the XSD in the source pane, and the desired target XML/XSD in the target pane
- insert an XSLT instruction 'apply-templates' and connect it to the root/item on the left and to the target element on the right
- in the text editor, move the xmlns:xsi declaration from the target element to the root xsl:stylesheet element, as we need it to be global
- right click on the 'dummybox' element and create a new template, using *[xsi:type='box'] as match expression
- mapper switches to the new template, so right click on the 'dummybox' and pick 'set as source context'
- right click on the target element, and pick 'set as target context'
- now drag a link between the 'weight' element to a child element of the target context
- create a new template also for the other type of 'item', with the same operations
- run the processing, and see that each 'item' was processed by a different template, using a different mapping created using drag & drop operations.

A sample XSL could be this one

<xsl:stylesheet version="1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<books>
<xsl:apply-templates select="root/item"/>
</books>
</xsl:template>

<xsl:template match="*[@xsi:type='box']">
<book>
<xsl:attribute name="pubdate">
<xsl:value-of select="weight"/>
</xsl:attribute>
</book>
</xsl:template>

<xsl:template match="*[@xsi:type='package']">
<magazine>
<xsl:attribute name="pubdate">
<xsl:value-of select="shape"/>
</xsl:attribute>
</magazine>
</xsl:template>
</xsl:stylesheet>

Hope this helps,
Alberto

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Borys MusielakSubject: Mapping complex document with multiple xsd:type's defined
Author: Borys Musielak
Date: 27 Oct 2008 01:29 PM
Alberto, thanks for your very detailed explanation. One thing worries me though. You are altering the schema to make it possible to map elements of different xsi:type. I cannot do it. I have a standard XSD schema defined by the FpML standard and I cannot really be altering it.

As far as I understood though, the altering is only for the purpose of making it possible to map the elements graphically in Stylus, am I correct?

So, in case a new version of FpML schema is release, we'd have to adjust it again to our needs, by manually specifying the (let's say) supported product types and all other elements that we would like to map visually. Am I correct? Please clarify if I'm wrong.

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Alberto MassariSubject: Mapping complex document with multiple xsd:type's defined
Author: Alberto Massari
Date: 27 Oct 2008 01:44 PM
Hi Borys,
yes, the schema is modified only to support the creation of links inside Mapper; the XSLT code doesn't depend at all on the schema used.
Keep in mind that the schema used in the left pane of mapper must not be the official FpML schema, but only a working (local) copy, and should be changed only in the parts you plan to use in mapper.

Alberto

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Borys MusielakSubject: Mapping complex document with multiple xsd:type's defined
Author: Borys Musielak
Date: 28 Oct 2008 06:07 AM
Thanks Alberto, it's all clear now.

Do you know, perhaps, if there are any plans to make it work without the need to manually modify the schema, in the future releases of the Studio? It seems like a missing feature, really and the solution presented seems like a workaround (and a non-obvious one, too).

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Alberto MassariSubject: Mapping complex document with multiple xsd:type's defined
Author: Alberto Massari
Date: 30 Oct 2008 10:10 AM
Hi Borys,
yes, this improvement is on the list of new features for Stylus, but it hasn't been yet scheduled for a specific version.

Thanks,
Alberto

 
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