If a foreign element contains non-DITA content, the non-DITA content
can be exported to a separate file and replaced in-line with an
object element. The data attribute of the
object element would reference the generated file, and the
type attribute of the object element would be set
to the value "DITA-foreign".

If an object element is present within the
foreign element during generalization, it is not included with
the content that is exported to the separate file. This original
objectelement is used to specify alternate content in publishing
systems that cannot display the foreign content. It would not be modified except as the
ordinary rules of generalization require it.

In the exported file, exported content would be enclosed within a root
foreign element in order to accommodate the possibility that it
might contain several main elements apart from the alternate content.

For easy recognition, the name of the exported file would start with
dita-generalized-

, and it is recommended that the file name also contain the topic
ID, specialization type, and element ID or generated identifier.

Example: Simple object generalization
For example, a DITA document could contain a specialization of
foreign for MathML using the MathML domain that ships with DITA
1.3. It could look like this:

<mathml class="+ topic/foreign mathml-d/mathml ">
<m:math>
<m:mi>x</m:mi><m:mo>+</m:mo><m:mn>3</m:mn>
</m:math>
<data-about>X plus three</data-about>
</mathml>
The mathml container is a DITA element, so it should be
generalized using normal rules. The m:math element, which is not a
DITA element, will be exported to another file. The data-about
element will remain:

<foreign class="+ topic/foreign mathml-d/mathml ">
<object data="dita-generalized-topicid_mathml1.xml" type="DITA-foreign"/>
<data-about>X plus three</data-about>
</foreign>
Contents of dita-generalized-topicid_mathml1.xml:
<foreign class="+ topic/foreign mathml-d/mathml "
xmlns:m="http://www.w3.org/1998/Math/MathML">
>
<m:math>
<m:mi>x</m:mi><m:mo>+</m:mo><m:mn>3</m:mn>
</m:math>
</foreign>
Example: Multiple object generalization
An object might also contain multiple object elements:

<mathml class="+ topic/foreign mathml-d/mathml ">
<m:math>
<m:mi>x</m:mi><m:mo>+</m:mo><m:mn>3</m:mn>
</m:math>
<data-about>X plus three</data-about>
<m:math>
<m:mi>y</m:mi><m:mo>-</m:mo><m:mn>2</m:mn>
</m:math>
</mathml>
The mathml container, which is a normal DITA element, should be
generalized using normal rules. A file should generated for each set of elements bounded by
the container and any existing object elements. In this case, two files will be generated,
and two new object elements added to the source.

The modified source:

<foreign class="+ topic/foreign mathml-d/mathml ">
<object data="dita-generalized-topicid_mathml1.xml" type="DITA-foreign"/>
<data-about>X plus three</data-about>
<object data="dita-generalized-topicid_mathml2.xml" type="DITA-foreign"/>
</foreign>
The contents of dita-generalized-topicid_mathml1.xml, the first exported file:

<foreign class="+ topic/foreign mathml-d/mathml "
xmlns:m="http://www.w3.org/1998/Math/MathML">
<m:math>
<m:mi>x</m:mi><m:mo>+</m:mo><m:mn>3</m:mn>
</m:math>
</foreign>
The contents of dita-generalized-topicid_mathml2.xml, the second exported file:

<foreign class="+ topic/foreign mathml-d/mathml "
xmlns:m="http://www.w3.org/1998/Math/MathML">
<m:math>
<m:mi>y</m:mi><m:mo>-</m:mo><m:mn>2</m:mn>
</m:math>
</foreign>