XLIFF 2.0 Comments - Ignorable

Honestly, I don’t quite understand the use of the <ignorable> element. Since it can hold <source> and <target> it seems like it would be a good mechanism to contain text which could be localized at one point,
 but shouldn’t be at this particular point and is included purely for context (e.g. surrounding content) to a <segment> that should be localized, but I’m not sure because there is no real example given for it in section 2.2.2.7 and the example that is given
 in section 2.8.1 still doesn’t make its use clear to me:

 

Content parts between segments are represented with the <ignorable> element, which has the same content model as <segment>.

For example:

<unit id="1">

<segment>

  <source>First sentence.</source>

  <target>Première phrase.</target>

</segment>

<ignorable>

  <source> </source>

</ignorable>

<segment>

  <source>Second sentence.</source>

</segment>

</unit>

 

I’m not sure what “content parts” means here.

 

Thanks,

Ryan