In addition to the mechanism for conditionally presententing parts of a
document the preservation of the current context was found to be necessary
for some reasons.
Preservation of the current context is a way of saving state information
which is sometimes needed in the stateless way the WWW works in.
It is needed to carry context information over a series of XHTML documents, especially when the current context contains information that is not used, i.e. known about, by the current document. If it is not used by the current document any link that go away from that document do not contain that information, it would be lost. For example, a series of pages with different languages, in the middle of that series there is one document that does not contain those languages. The information is not used and therefore would be lost in any link in that page. Quite often XHTML pages contain links into themselves, with only changing one attribute, preserving the state information would be very convenient.
The application "Folded Documents" actually needs this further extionsion to actually work. With the preservation of the current state of the document folds can be opened and closed independently of each other.
The problem is to pass all of the current context or parts of it on to the next document. the solution is actually quite simple the curent context is appended to every link in the section that is marked up for preservation of context.
Sometimes not all of the current context should be preserved. The
attributes that should be save can be specified in different ways. Any number
of explicitly defined context attributes can be preserved or all context
attributes in the current context that have a defined name.
For practical purposes the opposite operation to rembering context is also
introduced. This means that in a section that remembers certain attributes
some of these can explicitely not be passed onto the next document.