Update June 2009: Work has begun in earnest on the follow-on specification called BasicLTI. The good news is that BasicLTI is on a track to be an actual standard. While the BasicLTI specification is under development it is only available to members of the IMS Global Learning Consortium.
Some sample code has been developed for BasicLTI - this sample code is not the specification and everything is subject to change until the BasicLTI specification is released.
http://code.google.com/p/ims-dev/
SimpleLTI and BasicLTI will coexist during 2009 as SimpleLTI is out and in production in a few places. New projects should be looking at BasicLTI (IMS Membership required). If folks are not IMS members they can look at SimpleLTI - the high-level differences are that BasicLTI uses OAuth for its signing and only allows the "Direct" or POST option. So folks who are not IMS Members can use SimpleLTI to come up to speed with the architectural issues around LTI.
Once the BasicLTI spec is approved it will be made public.
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