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A simple personal database will be used to illustrate some of the
practical aspects of customizations via hooks.
The database contains information about
addresses, phone numbers, and electronic mail addresses
of persons, institutions, and companies.
The facility is implemented in Emacs Lisp,
and it is used as an integrated part of Emacs.
When writing letters, addresses can be extracted from
the database and be inserted into the letters; similarly when
sending electronic mail, the e-mail addresses can be
extracted from the database; and, finally, the database
can be used as an electronic phone directory.
A query on the personal database consists internally of two parts:
(1) extraction of information from the database, and
(2) utilization of the extracted information in some context.
Both parts are opened via the use of hooks.
When information has been extracted from the database
there is an intercepting hook, which
is able to modify the result before it is utilized.
As the default, the information is typically displayed in a new Emacs buffer,
but this may also be changed by procedures attached to the hooks.
Wed Mar 6 09:44:24 MET 1996