This section describes a mechanism for establishing cross-references between two or more documents via symbolic labels which are independent of the physical realisation of these documents. The documents involved may reside in remote locations and may be spread across one or more HTML files.
The mechanism is an extension of the simple label-ref pairs which can be used only within a single document. A symbolic label defined with a label command can be referred to using a ref command. When processed by LaTeX, each ref command is replaced by the section number in which the corresponding label occurred. When processed by the translator, each ref is replaced by a hypertext link to the place where the corresponding label occurred. The new commands detailed below show how it is possible to refer to symbolic labels defined with label in other external documents. Such references to external symbolic labels are then translated into hyperlinks pointing to the external document.
Cross-references between documents are established with the commands:
\externallabels{<URL to directory of external document>}
{<external document labels.pl file>}
\externalref{<label in remote document>}
The first argument to externallabels should be a URL to
the directory containing the external document.
The second argument
should be the full pathname to the labels.pl file belonging
to the external document. The file labels.pl associates symbolic
labels with physical files and is generated automatically for each
translated document
.
The command externallabels can be used once for each external
document in order to import the external labels into the current document.
The argument to externalref may be any symbolic label defined
in any of the external documents in the same
way that the ref command refers to labels defined internally.
After any modifications in an external document (sections added/deleted,
segmentation into different physical parts etc.) a new labels.pl
will be generated. If the externallabels command in another
document contains the correct address
to the labels.pl file then the cross-references will be
realigned
after running the local document through the translator. A warning is
given
if labels.pl cannot be found.