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Subject: Re: [docbook-apps] Spurious matches of CaseB/CaseF in select.olink.key.in.lang

Hi Alexey,

Yes, there is some value in $prefer.internal.olinks for some people. In this section of my book:


there is this description of the $prefer.internal.olink parameter:

"Another feature to support modular source files is the prefer.internal.olink stylesheet parameter. This is useful when you reuse a content module in more than one document. If you cross reference to such a module, you do not want to open another document if the content exists in the current document. Setting prefer.internal.olink to 1 causes the stylesheet to first test the current document's olink data to see if it has the id or xml:id value of the targetptr. If it does not, then the stylesheet falls back to the requested targetdoc data set."

So if $prefer.internal.olink = 1, then the olink's targetdoc attribute may be overridden by the value of $current.docid, if the target id is in the current document. I think that is why it links to itself in your case, even when the targetdoc attribute seems to point to another document. If you don't want that override behavior because in your case the elements with the same id have different content, then set $prefer.internal.olinks = 0. In general, the use case for $prefer.internal.olinks=1 is when you are reusing source modules that don't otherwise have duplicate id values, and you want the olinks to resolve close to home if possible. That's pretty specialized, so the param is set to zero by default.

One clarification: the value of targetdoc is independent of the value of @id on the root element of the source document. You may make them the same by convention if that is convenient, but the olink system does not assume that. The targetdoc values are only resolved in the olinkdb.xml file, by matching an <olink> element's @targetdoc in the source file to a <document> element's @targetdoc in the olinkdb.xml database file. So when you say:

even though the document ID is clearly different

I cannot tell if you are referring to the id attribute value in <book id="doc1">, which is irrelevant. What is important is if there is a <document targetdoc="doc1"> in your olink database. I suspect there is, but I want to make that distinction.

Regarding your question 1, Cases A and B (and E and F) may produce different results, and so the template keeps them separate so that the debug messages can distinguish between the cases.

Regarding your question 2, "internal" here means internal to the current source document being processed, and "external" means in another source document processed at a different time. It is a logical distinction at the source level. They may not be in the same physical source file: a document made up of many Xincluded modules would consider all ids found *after* resolution of Xincludes to be internal to the resolved document.

In FO output, links internal to the PDF file use <fo:basic-link internal-destination="id">, while external links use <fo:basic-link external-destination="url(...)". Linking among the chunks of a single source document would still be considered "internal" by this usage. The distinction for an external document is that the baseuri value from the olinkdb.xml file for that external document is added to the href value.

I hope I answered your questions.  If not, feel free to ask more.

Bob Stayton
Sagehill Enterprises

From: Alexey Neyman
Sent: Wednesday, August 28, 2013 1:29 PM
To: DocBook Apps
Subject: [docbook-apps] Spurious matches of CaseB/CaseF in select.olink.key.in.lang

Hi all,

I have a couple of documents with some element IDs overlapping. For example, both have "ch-overview" ID for the first chapter. I tried using $prefer.internal.olink, but it seems to misbehave on such links: it links to internal ID even if @targetdoc points to another document. For example:

<book id="doc1">
<chapter id="ch-overview">
<olink targetdoc="doc2" targetptr="ch-overview"/>

links to itself, even though the document ID is clearly different. The reason is that select.olink.key.in.lang template has CaseB/CaseF variables that ignore @targetdoc from <olink/> and use $current.docid instead, and cases B/F have higher precedence than cases A/E (that use olink/@targetdoc).

So, what is the purpose of $prefer.internal.olink, given that:

1. If a check for $current.docid = $targetdoc.att is added to cases B/F (to respect the document ID on the pointer), they become equivalent to cases A/E.

2. Even with $prefer.internal.olink = 0, links within the current document are converted to internal links by olink.as.linkend template in fo/xref.xsl (in the PDF output). I haven't experimented with HTML output - but I am not sure what would be the notion of "external" vs. "internal" link in, say, chunked HTML document.

Is $prefer.internal.olink some vestige of the past that should've been removed, or am I missing some value in it?


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