What can you filter?

Advanced reuse in DITA Lesson 1: Using conditions What can you filter?

The DITA filtering mechanism is quite powerful and flexible. You can use it to filter out almost any type of element in DITA topics and in DITA maps.

In DITA topics, some of the elements you can filter are:

sections
paragraphs
ordered and bulleted lists
list items
notes
tables
table rows
figures
images

In DITA maps and bookmaps, some of the elements you can filter are:

topic references
map references
key definitions
chapters and appendixes
frontmatter, backmatter, and their elements

Where to be careful

There are two areas where you need to exercise some caution in filtering: inline elements and elements that have required children.

It is not a good idea to filter inline elements. This is mostly a localization concern. The previous course (Introduction to reuse in DITA) covered this to some degree: what makes sense in one language when it is filtered out might not make sense (or translate well) when it is presented in another language.

You need to be careful when filtering elements that have required children, otherwise this might result in an invalid structure. If filtering removes required elements, it will result in an invalid topic. For example, if you add conditional attributes to all <li> elements in an unordered list (<ul>) and filtering removes them all, the empty <ul> element will be invalid. Other elements that have required children include <ol>, <sl>, <steps>, <substeps>, <properties>, <table>, <simpletable>. If you are not sure which child elements are required, check the DITA 1.2 specification.

What you cannot filter

There are a number of elements that cannot be filtered out. These include: