For the new subscribers and lurkers, here is a (hopefully) simple introduction to ISD, Objectivism, and Constructivism (with advance apologies to Mike Spector and Dave Jonassen for any heresies which might spring up).
As background, what ITForum is about is the discussion of issues associated with the use of technology in education, instruction, teaching, and or learning. And obviously, one of the major issue is how can we use technology effectively in an educational environment.
ISD (Instructional Systems Design or Development, depending on the book you read) is a methodology which describes a systematic approach to developing instructional materials, typically using the Analysis-Design-Development-Implementation-Evaluation (ADDIE) approach or sequence. This method is quite generic, and compares with systems used to develop a product (e.g., computer applications). Two of the major contributors to the ISD approach include Gagné and Merrill. The ISD approach also "appeared" when technology was very primitive and a methodological system was the best way to minimize delays. However, one of the criticisms of the ISD approach is that it is too systematic given the creative nature of interactive technologies. The converse to this argument is that instructional technology must be designed with the learner in mind, and therefore some form of theoretical framework is essential.
And this is perhaps where constructivism/objectivism comes in. In some ways, the two approaches represent a philosophical approach to the teaching-learning process: is it the teacher who transmits the knowledge to the learner (behaviorist) or is it the learner who should be empowered to construct knowledge (constructivist). This will probably generate a lot of criticism, but it seems to provide an initial comparison for new researchers.
From another perspective, one of my colleagues suggested that constructivism is now getting the criticism, so which way do you go? Here is the politically correct answer...
Focus on the outcomes you are trying to achieve with the learner, and develop strategies which you believe will most effectively and efficiently achieve those outcomes. If technology is a means by which the strategy can be implemented, then go for it. (Note that the technology itself is NOT a solution, but only a means to an end). The strategy you choose may then be behaviorist, cognitive, constructivist, or post-modernist.