The problem of linking to living
documents
See also: Annotation, Multiuser considerations
.
A problem arises when one user wants
to refer to a portion of another
document to which he does not have
write access. The reference to a
part of the document must remain
as valid as possible when the document
is updated.
The solution set is as follows: take
your pick.
The document is frozen.
This in fact applies nicely to mail
messages and news articles which,
once published, are unretractable.
You can refer to a part of these
messages by character range (line
and character etc).
Versions are kept.
If the document itself is not frozen,
one can still refer to a particular
version of it if a record of versions
is kept. This requires that the
server provdie an additional protocol
funtion, which is to tell a client
exactly which part (if any) of the
current version of a document is
the part corresponds to a particular
part of an older version. This translation
can be generated automatically by
the "diff" engine used by most source
code control systems. These systems
do not always work: a smart editor
would be able to keep better track.
This is an interesting option, because
the operations needed to do it are
the same as those needed for putting
links onto plain text documents and
keeping track of versions, both of
which are important aspects of collaborative
software design.
(See also: versioning )
The document is writable by the annotater.
In this case, when the person refering
to the document has write access
to it, he can insert marks. This
is the way the current (1992) NeXTStep
editor works: it embeds anchors in
the destination document. If the
document is later edited, the anchors
are moved around with the text, though
in some cases (drastic rewriting)
they can disappear.
Everything is numbered
This solution requires the author
(or rather, the author's editing
program) to give unique identifiers
to every part of a document which
can be the destination of a link.
This is not in fact a ridiculous
overhead if handled efficiently.
There must be a certain granularity
(paragrpah, for example) which prevents
people linking to precise words,
and this is a drawback.
Linking by context
In this case, the annotater refers
to a part of the document by the
context: for example, he quotes the
first and last pieces. See for, example,
the section "In this case...". This
method is clearly heuristic and prone
to failures just as is the automatic
generation of differences above..
Comment by: Kevin Altis