Relationships and commitments in learning object metadata

Learning objects are educational resources designed to support Web-based learning experiences. These experiences are made up of a number of activities that learners have to carry out to attain a given learning objective. Activities are specifically designed to be performed by (earner and staff roles, and take place in certain environments that define the available resources, including services and learning objects. Relationships among all the elements in a learning experience, such as roles, activities and environments, are important as they entail significant runtime commitments in learning systems. These relationships can be studied at the light of the well-known relationships among classes in object-oriented programming. Learning object design by contract, a technique intended to specify learning object metadata using assertions, is described in this paper as a mean to precisely specify relationships in learning object-based activities.