A learning object is a selfsuficient object that exists in the external world and holds some source of knowledge. It is a learning object because it has been designed in the purpose of getting a learner to internalize [learn] its content by interacting with it. They are expressions of a certain peagogic ‘intention’ . The clearer the intention is, the cleaner and more “to the point” the learningobject will be.
My golden rules for designing learning objects:
1. Have only one specific skill in mind when defining the goals of the learning object.
2. Be deliberate and limited with the modes of activity the learning object proposes to the learner.
3. Make sure the learning object makes sense equally as a stand alone obejct and as a part of a whole.
Somtimes definition of learning objects are very broad: any type of digital content that supports learning. 

The technological delivery of content is is surely an interesting factor, but the problem with that definition is that not all digital content is modular. A page in a school book that adheres to the rules mentioned above is more of a learning object than an online knowledge base or an informative website even though they can be said to support learning. The ‘learning object quality’ lies with is its clearity of intention, its purpose.

Object orientation in software development as in education is about reusability which leads tomodularity which gives flexibility.
David A. Wiley, ”Connecting Learning Objects to Instructional Design Theory”
“The main idea of ‘learning objects’ is to break educational content down into small chunks that can be reused in various learning environments, in the spirit of object-oriented programming”

The challenge, as I see it, in object-oriented programming as in e-learning development, is to break up the domain (subject matter) in the right way. You have to find (or invent) the right taxonomy for the skill set needed to master the subject and for the different modes of learning supporting the development of this skill set. To make learning objects that are both semantically independent and works in a pool of other learning objects, they should in their design, reflect an agent-based model of knowledge: Knowledge as a product of all our small understandings.

Understandingsare small and independent mental constructs, with a story and a life of their own. Understanding emerge in a network or hierarchy of existing understanding, but its position is relative, dynamic, on-going and mutable. Once they have emerged, they can be concieved as agents of knowledge, ready to serve the responding mind. When called for they contribute to the greater purpose of responding to the world. A given situation demands a unique selection and utilization of agents by the mind.
A good learning object should be embedable into a existing network of learning objects, and it should be designed as something that works like an agent.