# Considerations for generalizing `<foreign>`

elements

The `<foreign>`

element can contain a mixture of DITA and non-DITA
content. Non-DITA content that is contained within a `<foreign>`

element
cannot be generalized. However, the `<foreign>`

element itself, as well as
any DITA elements that it contains, can be generalized using normal rules.

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
`<object>`

element 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:

<mathmlclass="+ 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:

<foreignclass="+ topic/foreign mathml-d/mathml "><objectdata="dita-generalized-topicid_mathml1.xml" type="DITA-foreign"/><data-about>X plus three</data-about></foreign>Contents of dita-generalized-topicid_mathml1.xml:<foreignclass="+ 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:

<mathmlclass="+ 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:

<foreignclass="+ topic/foreign mathml-d/mathml "><objectdata="dita-generalized-topicid_mathml1.xml" type="DITA-foreign"/><data-about>X plus three</data-about><objectdata="dita-generalized-topicid_mathml2.xml" type="DITA-foreign"/></foreign>

The contents of dita-generalized-topicid_mathml1.xml, the first exported file:

<foreignclass="+ 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:

<foreignclass="+ 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>