Koha and the “magic” of XSLT : displaying new MARC fields on the OPAC.

A short tutorial on using XSLT to make MARC fields in your data visible on the OPAC.

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Earlier today, Suresh Kumar Tejomurtula, a member of the venerable LIS-Forum mailing list being run out of IISc Bangalore, posted a question on that list:

Under language codes of 008/35-37 and also under 041$a I added language code. for eg: tel for Telugu language. But I do not see any difference to the view of the record, except that the marc tags contains that values. Adding these fields data will enable library team to understand the language of the material. My question is, How will the users of the OPAC, who do not know about marc language codes will understand the item language [from just the 3-letter code sequence].

Short answer : Using XSLT

Much of Koha’s superpowers on the OPAC (as also on the staff client) side comes from its judicious use of XSLT. When we search for documents in Koha, the result that is returned from the database by way of the various perl modules that perform much of Koha’s internal plumbing, comes in as an XML (eXtensible Markup Language) document. More precisely it is returned as a MARCXML record. Readers of this blog who are familiar with the MarcEdit software may have often encountered a MARCXML record. Those who are not so familiar may well like to read up a bit from here before proceeding with this post.

So what is XSLT?

Wikipedia gives the definition of XSLT as –

“XSLT (Extensible Stylesheet Language Transformations) is a language for transforming XML documents into other XML documents, or other formats such as HTML for web pages, plain text or XSL Formatting Objects, which may subsequently be converted to other formats, such as PDF, PostScript and PNG.”

Where to start?

At the OPAC level, the XSLT magic is primarily driven by two files i.e. (a) MARC21slim2OPACResults.xsl and (b) MARC21slim2OPACDetail.xsl. Koha’s default settings of how we see the search results on the OPAC and the document specific details in the Normal view, are defined in these two files.

N.B. Directly editing these two files is strictly not advised unless you are a XSLT guru.

Lucky for us that Koha’s system preferences provide options to override the defaults by creating new XSLT files and telling Koha to use the new ones instead. The screenshot below shows the default setting.

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The two files are available inside a folder named xslt under the locale of the selected theme you are using e.g. /usr/share/koha/opac/htdocs/opac-tmpl/bootstrap/en/xslt/ on a package-based installation. By default most of us in India would be using the English locale i.e. “en”. The default Koha theme is “bootstrap”. Thus if you are using a custom theme and/or different locale look for the files under that.

Step #1 : Copying the XSLT files

We will be fetching the 3-letter language code from MARC 008/35-37 of each marc record. Since our Koha instance here is named as “demo”, we’ll make a copy of the file MARC21slim2OPACResults.xsl as MARC21slim2OPACResults-demo.xsl and the MARC21slim2OPACDetail.xsl as MARC21slim2OPACDetail-demo.xsl.

N.B. You can give any name to the copies you make, but it is suggested that the less adventurous you are with the names, easier it will be for you to trace your steps back if you make a mistake while editing them. And trust me you will make mistakes, at least initially.

Step #2 : Editing MARC21slim2OPACResults-demo.xsl

The MARC21slim2OPACResults.xsl is what drives the display of results of a search on the Koha OPAC. And it does not show the value of 008/35-37 i.e. MARC language code, while displaying the search result. To add this facility, we need to do the following to our copy i.e. MARC21slim2OPACResults-demo.xsl. Around line no. 70 or there about, there will be this line <xsl:variable name="controlField008-30-31" select="substring($controlField008,31,2)"/>. Add the following line after it – <xsl:variable name="controlField008_35-37" select="substring($controlField008,36,3)"/>.

Explanation: we’re defining a new variable named controlField008_35-37 and in it we are storing the 3-digit value found at 008/35-37 from another variable – controlField008.

The second step in editing this file is to add the code to check if (a) 008/35-37 actually exists (e.g. if you have a blank 008 field, 008/35-37 won’t exist) and (b) it is set as something other than “und(i.e. undefined). The following code does that first and proceeds to match the value found in 008/35-37 against 23 different languages. These languages are English and the 22 official languages of India as per the Eighth Schedule of the Indian Constitution. You can add or remove any language from this list as you require. However, when you do, please make sure that the codes you setup in this list here are coming from the Code Sequence document of the MARC Code list for languages as published by the US Library of Congress.

This means that you must also be using these same exact codes in your MARC records in Koha.

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Where we place this code will depend on where we want this language to listed in the results. In our case, we decided to add it between Material type and Format. And thus in our case, the code was added at line no 637. If you too want language to be displayed between the Material Type and Format, then look out for this line <xsl:if test="string-length(normalize-space($physicalDescription))"> and add this block before.

Saved the file and moved on to the next section.

Step #3 : Editing MARC21slim2OPACDetail-demo.xsl

The process is similar to what we just did above. Open the file MARC21slim2OPACDetail-demo.xsl for editing and go to line no. 51 (or there about) and look for this line <xsl:variable name="controlField008" select="marc:controlfield[@tag=008]"/>. Add the following line immediately after that: <xsl:variable name="controlField008_35-37" select="substring($controlField008,36,3)"/>.

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Since we wanted the “Language of document” to come after Material type, we added the code immediate after the node <xsl:if test="$DisplayOPACiconsXSLT!='0'"> is closed but before <!--Series: Alternate Graphic Representation (MARC 880) -->; in our case, this worked out to be around line no. 195. Finally, we saved and closed the file.

Getting Koha to use the new XSLT files

The Koha system preference OPACXSLTResultsDisplay was changed from its original setting (i.e. “default”) and set to the path of our new file MARC21slim2OPACResults-demo.xsl i.e. /usr/share/koha/opac/htdocs/opac-tmpl/bootstrap/en/xslt/MARC21slim2OPACResults-demo.xsl. Likewise the other system preference OPACXSLTDetailsDisplay was changed to /usr/share/koha/opac/htdocs/opac-tmpl/bootstrap/en/xslt/MARC21slim2OPACDetail-demo.xsl. It was time to test our XSLT modifications.

And it works!

Since pictures are said to be worth a 1000 words, we will let before and after screen grabs do the talking here. Also if anyone wants to see directly how it actually looks after applying the changed XSLT, visit the URL http://demo-opac.l2c2academy.co.in/cgi-bin/koha/opac-detail.pl?biblionumber=18

Before : Using the default MARC21slim2OPACResults.xsl

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After : Using the new MARC21slim2OPACResults-demo.xsl

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Before : Using the default MARC21slim2OPACDetail.xsl

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After : Using the new MARC21slim2OPACDetail-demo.xsl

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