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Implementing Content Reuse
in DITA: The Nuts and Bolts
Dan Dionne
UTS Technical Team Lead
IBM Silicon Valley Lab
Agenda
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Effective reuse of information
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Barriers to reuse
DITA designed for reuse
Reuse problems and solutions
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Element-level reuse
Conditional reuse
Topic-level reuse
Map-level reuse
Content reuse in DITA
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Effective reuse of information—why we
aren’t there yet
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Duplicate maintenance of information is
expensive
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Authoring time
Maintenance!
Consistency
Boilerplate reuse a general practice for nontechnical content
Effective reuse of technical content remains
elusive
Content reuse in DITA
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Barriers to reuse
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Unstructured authoring technologies are unsuitable for reuse
Even structured authoring technologies (SGML) throw up many
obstacles
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Team communication issues. The smaller the scope, the easier.
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Inconsistent and contradictory use of conditionality and other
attributes
Information too thoroughly imbedded in a hierarchy
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Information is written in a larger context, such as a chapter
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How to break out reusable chunks?
Linking issues
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What do you link to?
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How do you maintain hard-coded links?
External dependencies
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Entities of all kinds
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Book-metaphor structures
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DITA is designed to enable reuse
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Information design
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Modular topics are complete in themselves
Typed topics promote consistency of information
coverage
Technical design
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Elimination of most external dependencies, with
improved management of the dependencies that
remain
Flexible link management through ditamaps
eliminates hard-coding of links
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Reuse problems and solutions
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Based on reuse experience from the IBM
Information Management community
Needs
Technical solutions
Best practices
Content reuse in DITA
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Element-level reuse
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Problem: Teams need to reuse information at
the most granular level (paragraphs, phrases,
notes)
In SGML, we created text entities for this sort
of information
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!ENTITY prodname “Name of the product this
week”
Worked well at the book and library level, but was
a disaster when integrating information across
product boundaries.
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DITA solution: content referencing
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Any element can be a pointer to another
element in another file by using the conref
attribute
The reference includes a relative pathname if
needed
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<ph conref="../reuse/common.dita#common/
prodname/>
Clever trick: Use the search path file to switch
to a different common file for different outputs
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Content referencing best practices
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Content referencing outside the file creates an external
dependency. Any element in any file can reference any matching
element in any other file—spaghetti code!
To simplify dependencies, create a single mixed/combination
topic for all reusable information in your information set
 Use a combination topic because it will allow you to create as
many of the typed topics as you need, all in one location
 Give the combination topic an obvious name
 You must include the content referencing topic in your ditamap.
But set it to toc=no, print=no, and linking=none so it never
appears to the end users
Typing in the full conref string is error-prone. Use linking tools in
your editor or create macros to insert the content references
Phrases (<ph>) are the easiest elements to reuse, in almost any
context
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Demonstration:
element-level reuse
Content reuse in DITA
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Conditionality
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Problem: Near-identical information can be
used in multiple situations.
Solution: Conditional coding
Problem: Need to differentiate conditions in
the output
Solution: Conditional coding with flagging
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DITA and conditionality
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Basic conditional coding is the same for DITA
as for other SGML and XML
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Multiple axes of conditionality available
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Restriction: no Boolean logic for conditions; can
include multiple conditions, but relationship is a
simple OR
Audience, platform, product, and otherprops
attributes
Filtering metadata also at the topic level
(more later)
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Conditionality inside topics
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Audience, platform, product, and otherprops attributes available
 No fixed values
 Best practice: use same values as filtering elements
 Best practice: use semantically useful values
In run-time ditaval file, can set each value to include, exclude, or
flag
 The default is include
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Best practice: teams should share values
Best practice: check your spelling! The system will not tell you when
you have an undefined value
Flag associates an image with the value
Best practice: use multiple ditaval files with semantically useful
names
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Demonstration:
conditionality in DITA
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Topic-level reuse
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Problem: entire topics need to be reused in
different venues
Solution 1: include the topic in multiple
ditamaps
Solution 2: include the topic in multiple
ditamaps, but activate filtering
Solution 3: reuse the topic inside a
combination topic
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Reusing a topic in multiple ditamaps
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This is the whole point of ditamaps and modular topics
A topic can be inserted in any ditamap as long as the pathing is
clear
 Simple relative paths are best, but the system can handle more
complex situations with search paths
 Verify that conditions and revisions are consistently defined
External dependencies need to be accommodated
 Reuse files need to be inserted in the ditamap as well
 Inline links may break
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Best practice: never code inline links (use maps and relationship
tables for all linking except to known external targets)
Graphics are handled by reference, so make sure they are
available as well
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Include topics in multiple ditamaps with
filtering
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If the topics need to vary depending on their context, include filtering in
the metadata
Metadata can be in the topic prolog or the ditamap
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Audience element includes
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Experiencelevel, job, otherjob, type, othertype, name
<audience experiencelevel=“expert” job=“troubleshooting”
type=“programmer”
Use “otherjob” and “othertype” to create your own labels
Prodinfo element includes sub-elements
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Best practice: always one or the other, never both. Experience suggests
that the topic prolog is best overall
<prodinfo><prodname>My product</prodname> <vrmlist><vrm
modification=“2” release=“3” version=“5.0</vrm></vrmlist></prodinfo>
Set build-time filters to build customized output
Eventually, set run-time filters to display customized output
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Demonstration:
filtering in DITA
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Imbed topics inside combination topics
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A mixed/combination topic can contain any number or
combination of any other topic types in any order
A combination topic is output as a single XHTML page
 The title is the title of the first topic in the set
 Caveat: users may not know to scroll through a long combination
topic
Topics can be authored exclusively in combination topics, but
more often are pulled into special-purpose combination topics to
serve a dual purpose
Tutorial example
Useful tip: if you have information that needs to be broken up into
multiple topics of different types, create a combination topic and
create new topics in it as needed. Then save each topic out to a
separate file.
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Demonstration:
combination topic with reused topics
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Map-level reuse
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The highest level of reuse is achieved through architecting and
reusing entire maps
Any number of maps can be imbedded in a map
 Pathing is the only real technical issue. It’s best to have a central
repository where all the maps and topics will come together
The hard part is information design
 Set map scope at appropriate levels
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“book” level maps are too high a scope
“chapter” level maps work better
Relationship tables can cross scope boundaries
Design maps according to the information design
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Each map should represent a distinct point in the navigation
An information architect should manage the top levels of the map
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Demonstration:
map-level reuse
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Summary
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DITA solves or eases many of the technical
problems associated with reuse
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Element-level reuse
Conditionality
Topic-level reuse
Map-level reuse
Communication between teams remains
critical
Good information design is the most
important aspect of all
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