[oXygen-user] XPath-validation in non-XSLT-files

[George Cristian Bina]

Dear Theun,

The XSLT validation performed by oXygen tries to create a Transformer 
object out of the edited XSLT stylesheet. This performs a more powerful 
checking of the XSLT document (compared with for instance a validation 
against a specific schema) and the XSLT processor used for validation 
reports also XPath errors. The XPath content completion that oXygen 
offers on XSLT files is strongly related with the fact that the edited 
file is an XSLT document. From the associated transformation scenario we 
identify the document that can be the input for the stylesheet and we 
determine possible elements and attributes from there, we also take into 
account the XSLT instruction that change the context in order to offer 
correct completion proposals.

As you see in the above description, both the validation and the content 
completion cannot be de-coupled from the XSLT editor immediately so the 
answer is no, you cannot have XPath validation and XPath content 
completion in the XML editor.

However, there are a couple of things you can do.

You can write a stylesheet to extract your XPath expression and generate 
as output another stylesheet that contains those XPath expressions 
associated eventually with information to easily identify where those 
XPath expression were extracted from. Then validate the generated 
stylesheet and if you find problems use that identification information 
to locate the expression in the original document.

Another possibility is to take advantage of the fact that oXygen 
supports XPath 2.0 for Schematron using Saxon 8 and create an XML Schema 
with embedded Schematron rule and use the saxon:expression function to 
test that a specific value is an XPath expression, you can find below an 
example of this approach.

XML Schema with embedded Schematron rules test.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
   <xs:annotation>
     <xs:appinfo>
       <ns xmlns="http://www.ascc.net/xml/schematron" 
uri="http://saxon.sf.net/" prefix="saxon"/>
     </xs:appinfo>
   </xs:annotation>
   <xs:element name="test">
     <xs:complexType>
       <xs:sequence>
         <xs:element ref="xpath" maxOccurs="unbounded"/>
       </xs:sequence>
     </xs:complexType>
   </xs:element>
   <xs:element name="xpath">
     <xs:annotation>
       <xs:appinfo>
         <pattern xmlns="http://www.ascc.net/xml/schematron" 
name="testXPath">
           <rule context="xpath">
             <assert test="saxon:expression(@expression)">Invalid XPath 
expression!</assert>
           </rule>
         </pattern>
       </xs:appinfo>
     </xs:annotation>
     <xs:complexType>
       <xs:attribute name="expression" type="xs:string"/>
     </xs:complexType>
   </xs:element>

</xs:schema>


test.xml

<?xml version="1.0" encoding="UTF-8"?>
<?oxygen SCHSchema="test.xsd"?>
<test xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation="test.xsd">
   <xpath expression="test;"/>
   <xpath expression="test"/>
   <xpath expression="test"/>
</test>

reported error:

SystemID: E:\george\test\p2\test.xml
Description: Static error in XPath expression supplied to 
saxon:expression: XPath syntax error at char 4 in {test;}:
     Unexpected token ";" beyond end of expression

The problem is that there is no tracing from the error to the source and 
all you can do is to get the expression between curly braces in this 
case test; and find it in your document.

Hope that helps,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
http://www.oxygenxml.com


Theun Fleer wrote:
> Hello,
>  
> When editing XLST-files in oXygen7.2 on WinXP the XPath-expressions in
> the "select" and "match" attributes can be validated. When typing an
> incorrect XPath-expression, a wavy yellow line is shown, and an error
> description at the bottom of the screen; "content completion" is also an
> option.
>  
> We are currently editing non-XSLT-files: a custom XML format with a
> custom namespace in which we must edit a lot of long XPath-expressions.
> We would like the same validation options as in the XLST-files... is
> this possible, and how?
>  
> Kind regards, and keep up the good work!
>  
> Theun Fleer
> Daidalos BV, The Netherlands
>    
>  
> Drs. T. Fleer
> Consultant
> GSM: +31 (0)6 40 58 50 27
>  
>  
> 
> Daidalos BV
> Source of Innovation
> Hoekeindsehof 1-4
> 2665  JZ  Bleiswijk
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> 
> 
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