Apply templates not working as desired

Question

Given the following xml inputs: file1:

<?xml version="1.0" encoding="UTF-8"?>


<File1 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

    <code code="file1_code" displayName="file1_display" codeSystem="file1_cs" codeSystemName="file1_csn"/>

    <title>Title of file1</title>   
    <component typeCode="COMP">
        <structuredBody classCode="DOCBODY">
            <component typeCode="COMP">
                <section>
                    <templateId root="someRoot_file1" assigningAuthorityName="someAuhthority_file1"/>
                    <code code="file1-sec1_code" displayName="file1_sec1_display" codeSystem="file1_sec1_cs" codeSystemName="file1_sec1_csn"/>
                    <title>Tile of sec 1 from file1</title>
                    <text>
                        <content styleCode="Italics">
                            Text of sec 1 from file1
                        </content>
                    </text>             
                    <entry> file 1 sec 1                    
                    </entry>
                </section>
            </component>
            <component typeCode="COMP">
                <section classCode="DOCSECT">                   
                    <code code="file1_sec2_code" codeSystem="file2_sec2_cs" displayName="file2_sec2_display" codeSystemName="file2_sec2_csn"/>
                    <title>Tile from sec 2 file 1</title>
                    <text>
                        <content styleCode="Italics">
                            Text from file1 sec 2
                        </content>
                    </text>
                    <entry typeCode="test"> file2 sec 2
                    </entry>
                </section>
            </component>
        </structuredBody>
    </component>
</File1>

file2:

<?xml version="1.0"?>
<A>
<title value="Title of file2"/>
    <text>
        <status value="generated"/>
        <div xmlns="http://www.w3.org/1999/xhtml">
            <p>File 2 Text</p>          
        </div>
    </text>
    <section>
        <code>
            <coding>
                <system value="sec 1 file2 sys"/>
                <code value="sec 1 file 2 code"/>
                <display value="sec 1 file 2 display"/>
            </coding>
        </code>
        <title>Title of sec 1 file2</title>
        <text>
            <content styleCode="Italics">Section 1 Text
            </content>
        </text>         
        <entry>
            <someEntry>                 
            </someEntry>
        </entry>
    </section>
    <section>
        <code>
            <coding>
                <system value="sec 2 file2 sys"/>
                <code value="sec 2 file 2 code"/>
                <display value="sec 2 file 2 display"/>
            </coding>
        </code>
        <title>Title of sec 2 file2</title>
        <text>
            <content styleCode="Italics">Section 2 file2 Text
            </content>
        </text>         
        <entry>
            <someEntry> entry sec 2 file 2              
            </someEntry>
        </entry>
    </section>

</A>

and the following xslt:

    <xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
        <xsl:output method="xml" indent="yes"/>

        <xsl:strip-space elements="*" />

        <xsl:variable name="input" select="/" />

        <xsl:template match="@*|node()">
            <xsl:copy>
                <xsl:apply-templates select="@*|node()"/>
            </xsl:copy>
        </xsl:template>

        <xsl:template match="/">
            <Bundle>
                <id value="test"/>          
                <type value="document"/>
                <entry>             
                    <resource>                  
                        <xsl:apply-templates select="document('file2.xml')/*"/>             
                    </resource> 
                </entry>
            </Bundle>
        </xsl:template>


        <xsl:template match="text">
            <text>
                <status value="generated"/>
                <div xmlns="http://www.w3.org/1999/xhtml">
                    <p>This is the text from the stylesheet </p>                
                </div>
            </text>
        </xsl:template>

        <xsl:template match="title">
            <xsl:apply-templates select="$input/File1/title"/>
        </xsl:template>

        <xsl:template match="section[1]">
            <xsl:apply-templates select="$input/File1/component/structuredBody/component/section"/>
        </xsl:template>

        <xsl:template match="section[2]"/>      

        <xsl:template match="File1/title">
            <title>
                <xsl:attribute name="value">
                    <xsl:value-of select="." />
                </xsl:attribute>
            </title>
        </xsl:template>

        <xsl:template match = "File1/component/structuredBody/component/section">       
            <section>
                <xsl:apply-templates/>
            </section>
        </xsl:template>


    </xsl:stylesheet>

And this is the output:

<?xml version="1.0" encoding="UTF-8"?>
<Bundle>
    <id value="test"/>
    <type value="document"/>
    <entry>
        <resource>
            <A>
                <title value="Title of file1"/>
                <text>
                    <status value="generated"/>
                    <div xmlns="http://www.w3.org/1999/xhtml">
                        <p>This is the text from the stylesheet </p>
                    </div>
                </text>
                <section>
                    <templateId xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" root="someRoot_file1" assigningAuthorityName="someAuhthority_file1"/>
                    <code xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="file1-sec1_code" displayName="file1_sec1_display" codeSystem="file1_sec1_cs" codeSystemName="file1_sec1_csn"/>
                    <title value="Title of file1"/>
                    <text>
                        <status value="generated"/>
                        <div xmlns="http://www.w3.org/1999/xhtml">
                            <p>This is the text from the stylesheet </p>
                        </div>
                    </text>
                    <entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
                </section>
                <section>
                    <code xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="file1_sec2_code" codeSystem="file2_sec2_cs" displayName="file2_sec2_display" codeSystemName="file2_sec2_csn"/>
                    <title value="Title of file1"/>
                    <text>
                        <status value="generated"/>
                        <div xmlns="http://www.w3.org/1999/xhtml">
                            <p>This is the text from the stylesheet </p>
                        </div>
                    </text>
                    <entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" typeCode="test"/>
                </section>
            </A>
        </resource>
    </entry>
</Bundle>

And this is the expected output:

<?xml version="1.0" encoding="UTF-8"?>
<Bundle>
    <id value="test"/>
    <type value="document"/>
    <entry>
        <resource>
            <A>
                <title value="Title of file1"/>
                <text>
                    <status value="generated"/>
                    <div xmlns="http://www.w3.org/1999/xhtml">
                        <p>This is the text from the stylesheet </p>
                    </div>
                </text>             
                <section>
                    <templateId xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" root="someRoot_file1" assigningAuthorityName="someAuhthority_file1"/>
                    <code xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="file1-sec1_code" displayName="file1_sec1_display" codeSystem="file1_sec1_cs" codeSystemName="file1_sec1_csn"/>
                    <title>Tile of sec 1 from file1</title>
                    <text>
                        <content styleCode="Italics">
                            Text of sec 1 from file1
                        </content>
                    </text>             
                    <entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
                </section>
                <section>
                    <code xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" code="file1_sec2_code" codeSystem="file2_sec2_cs" displayName="file2_sec2_display" codeSystemName="file2_sec2_csn"/>
                    <title>Tile from sec 2 file 1</title>
                        <text>
                            <content styleCode="Italics">
                                Text from file1 sec 2
                            </content>
                        </text>
                    <entry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" typeCode="test"/>
                </section>
            </A>
        </resource>
    </entry>
</Bundle>

I have the following questions:

1. Why is the title in the section elements coming from the main title (i.e. File1/title) when the apply templates is within File1/component/structuredBody/component/section? I was expecting that the title of the section will be output, which is what is desired. Even more confusing is that it does indeed output the elements in the section like code, entry and so on but title and text (see q2 below) seems to be treated differently and I can't for the life of me understand why.

2. Same with text. Why is the text for section not being output?

Here is my presumably false understanding of the process:

We start with the <xsl:template match="/"> and create elements Bundle, id etc. and then using <xsl:apply-templates select="document('file2.xml')/*"/> we match the top element of file2 (A) and since we don't have a template matching it explicitly, the identity template is called, copies it and process its child elements, which are text, title and section. For each of these child elements, it looks for a matching template. it finds them and matches them.

For element section however, it matches only the first section element because of <xsl:template match="section[1]"> and then because of <xsl:apply-templates select="$input/File1/component/structuredBody/component/section"/> in the template, it looks for a template matching children of section in FIle1, which are code, text, title and templateId. It finds no such explicitly defined template, so calls the identity templates for them, copies and processes them till the end. At least that is my understanding of it.

Answer 1

@ michael.hor257k and @Michael Kay yeah, that was definitely the case, that I misunderstood how xsl:apply-templates works with regards to context . I thought because I called the xsl:apply-templates from within xsl:template match = "$input/File1/component/structuredBody/component/section"> that it will only look for match templates that match the children of section. In other words, I thought it will look for templates like “<xsl:template match=”File1/component/structuredBody/component/section/title"> but that is clearly not the case.

xsl:apply-templates simply looks for the children and then looks for a match template regardless of the context from which they were called. So, it will look for title or text template that matches and if it finds them, it will match them.

The easiest solution I could find that seems to solve the problem is to add a path to the title and text templates. In other words, instead of just <xsl:template match="text"> I should have <xsl:template match="A/text">. Same for title. This way, the xsl:apply-templates will not apply <xsl:template match="A/text"> as the title in section is not a child of A. So given that no matching explicit template is defined, the identity template will be applied and will output the title of section as desired.

Answer 2

Why is the title in the section elements coming from the main title

Because any time the processor is instructed to apply templates to a title, it looks for the best-matching template to apply, and finds this:

<xsl:template match="title">
    <xsl:apply-templates select="$input/File1/title"/>
</xsl:template>

This changes the context to the title in File1.xml, and the best-matching template for this one is:

<xsl:template match="File1/title">
    <title>
        <xsl:attribute name="value">
            <xsl:value-of select="." />
        </xsl:attribute>
    </title>
</xsl:template>

and that is the result you see.

---

Same with text. Why is the text for section not being output?

-- edited in response to the following clarification: --

When I say text I am talking about text elements only.

The original text element (child of section in File1.xml) is not being output because you have a specific template matching it and outputting something else instead:

<xsl:template match="text">
    <text>
        <status value="generated"/>
        <div xmlns="http://www.w3.org/1999/xhtml">
            <p>This is the text from the stylesheet </p>                
        </div>
    </text>
</xsl:template>