The problem with using an expiration date to lock a demo is that the user
only needs to turn back the computer's system date to an acceptable one in
order to use your demo indefinitely. You may want to consider other methods
for your demos. Tony Toews describes his approach to locking demo files on
this Web page:
http://www.granite.ab.ca/access/demo.htm.
At Q-Built Solutions, we use Microsoft Access foibles to our advantage for
our Access database demos. Our demos are fully functional MDE's, but with a
pre-defined limit. The pre-defined limitation is built into the demo
itself, because users can always alter the system date, or make changes to
the Windows Registry or some configuration file, even if encrypted keys are
used.
Our developer tool demos will _only_ work on our demonstration database file
and no other. Users can add/change/delete records, tables and queries in
the demo database file to their heart's content to simulate the developer
tool's capabilities in their own environment. Users can change the file
names, move the files to any directory on the workstation or network, add
enough records to let the file size grow to the maximum limit, et cetera,
and the demo development tool will continue to work, but _only_ on the demo
database file -- until it's compacted.
For non-developer tool demos, the demo database has a pre-defined number of
uses built into the database. Users are free to add/change/delete records,
tables and queries in the demo database file while using the full features
of the application up until the maximum number of uses is reached, and then
the database compacts itself. Any subsequent attempts to use the database
application will result in very limited functionality and the message that
the demo has expired and to contact Q-Built Solutions for the full version.
No attempt to change the system clock or make other changes to the database
will remove the demo's "expired" status.
The "full-featured demos work until they are compacted" method has been very
effective for our demos, and we've considered licensing the technology to
other Access developers, but the market is probably extremely small, so
we've never bothered. In case you are interested in this approach to
distributing demos, you can download a few of our developer tool demos from
the following Web page to see how effective they are after the demo database
file "expires" from compaction:
http://www.Access.QBuilt.com/html/products.html
HTH.
Gunny
See
http://www.QBuilt.com for all your database needs.
See
http://www.Access.QBuilt.com for Microsoft Access tips.
(Please remove ZERO_SPAM from my reply E-mail address, so that a message
will be forwarded to me.)
