We are talking about learning activities, pedagogical approaches, and how to support those using Sakai services and tools. I highly recommend to the pedagogy discussion group to look deeply to the IMS Learning Design (LD) standard. It is an XML based standard on how to design learning activities. It provides a conceptual model for the description of teaching and learning processes. IMS delivers XML schemas as an integral part of all its specifications. As a result, the learning designs of courses are expressed in XML to make the course machine-readable. This means that courses encoded using LD can be processed by runtime engines, making the delivery management of courses more efficient. In LD, a unit of learning (UOL) refers to a complete, self contained unit of education or training, such a course, a module, a lesson, etc.

IMS Learning Design relies on a number of elements. These include: roles that people perform (who does what); activities (what they do); and environments, which include where they do them (services) and what they do them with (learning objects). The overall scenario or design is described within the method element, which contains play, act, and role-parts elements, and is analogous to a theatrical play. A learning design may be based around the achievement of specified learning objectives by learners; it may also define prerequisites. As well as allowing an entire design to be shared or reused, IMS Learning Design allows these elements to be reused in other learning designs.

I am asking if the use of learning design can be a guide to build a set of common services and tools on top of that to support learning activities in connection with content stored in repositories as learning objects.
these are some links to current work in LD :

The specification : http://www.imsglobal.org/learningdesign/index.html
UNFOLD project : http://www.unfold-project.net:8085/UNFOLD
Reload LD editor : http://www.reload.ac.uk/
CopperCore LD engine : ­http://coppercore.org/
LAMS authoring and run-time environment : http://www.lamsfoundation.org/ is "inspired by" LD and is supposed to be brought into conformance with the spec RSN
Learning Design book : http://www.springeronline.com/sgw/cda/frontpage/0,11855,5-146-22-36633821-0,00.html