XSLT 2.0 function to insert attributes and values

NVAudiophile · April 17th, 2013, 04:12 PM

Greetings,

I am new to XSLT 2.0 development and am trying to understand how I can write functions that modify the attributes of a text node. I would like to write a function that accepts four string values. I would like the function to then insert four pre-defined attributes, the values of which correspond with the string values the function received when it was called.

I have managed to write and invoke a function that does something similar to this as part of an xsl:copy instruction. The problem is that this results in a duplicate copy of the element and its text, when all I want to do is modify the nodeâs attribute set.

I attempted to call the function within an xsl:value-of select=âmy-function-callâ, however this construct only returns the text of the current node and does not make any changes to the nodeâs attributes.

Is it possible to write a function that performs this operation in XSLT 2.0?

Most of my work has been in other languages. I would typically approach this problem by calling a method that adds the desired attributes and attribute values to a given XML node. I am obviously confused by the parameter passing and return mechanism in XSLT 2.0.

Thanks in advance,

Martin

mhkay · April 17th, 2013, 05:47 PM

It looks as if you haven't understood the XSLT processing model. XSLT transforms an input document to create an output document. It's a very clean functional language (the stylesheet is a function whose input is the input document and whose result is the output document). As such there is no mutation of state.

If you are having difficulty seeing how to achieve a transformation in this style, then if you describe the requirements I'm sure we can help you.

NVAudiophile · April 17th, 2013, 06:18 PM

Hi Michael,

Thank you for your reply.

My objective is to add attributes and attribute values to an XML source document that will specify pre-defined typographic styles to apply when the modified source is submitted to a high-end page composition system.

I can add the necessary attributes and attribute values directly in the template as follows:

Code:

   <xsl:template match="act-name">
        <xsl:copy>
            <xsl:copy-of select="@*"/>
            <xsl:attribute name="BaseFormat" select="string('6201')"/>
            <xsl:attribute name="Style" select="string('40')"/>
            <xsl:attribute name="Typeface" select="string('32')"/>
            <xsl:attribute name="Variant" select="string('1')"/>
        <xsl:apply-templates/>
        </xsl:copy>
    </xsl:template>

However, for the sake of readability, and ease of maintenance, I would rather perform the same operation through a function call. Also, rather than specify the names of the attributes each time, I would rather have the function supply the attribute names (they are always the same) and simply pass in the values (which change).

So my function call would look something like:

Code:

<xsl:value-of select="myfunction:add-attributes('6201','40','32','1'))"/>

Except I haven't been able to get this to work.

The reason for this madness, by way of background, is to move the intelligence out of the composition system up into the web server that is receiving and submitting jobs to the system. We will use the Saxon .Net component to perform the transform. Each typographic style is encoded in XML and maintained in a database under revision control. When a job is submitted, the source will be transformed, the appropriate styles fetched from the database, and the entire package submitted for composition.

I hope this helps clarify things.

(I am reading your XSLT 2.0 and XPath 2.0 4th ed. book and find it most helpful.)

Thanks,

Martin

mhkay · April 17th, 2013, 06:39 PM

Named templates and functions are pretty well identical in what they can do, the only difference is in how they are called. You could write your function as

Code:

<xsl:function match="f:act-name" as="element()">
<xsl:param name="e" as="element()"/>
<xsl:param name="b" as="xs:string"/>
<xsl:param name="s" as="xs:string"/>
<xsl:param name="t" as="xs:string"/>
<xsl:param name="v" as="xs:string"/>
<xsl:for-each select="$e">
        <xsl:copy>
            <xsl:copy-of select="@*"/>
            <xsl:attribute name="BaseFormat" select="$e"/>
            <xsl:attribute name="Style" select="$s"/>
            <xsl:attribute name="Typeface" select="$t"/>
            <xsl:attribute name="Variant" select="$v"/>
        <xsl:apply-templates/>
        </xsl:copy>
</xsl:for-each>
</xsl:function>

You have to pass the element as a parameter because functions (unlike templates) aren't passed the context item as an implicit argument.