ISIS-TUTOR (Brusilovsky & Pesin 1994)
The ISIS-tutor is a hypermedia-based intelligent learning environment. The system integrates a tutoring component for directing study which presents problems to the student, a hypertext component which allows for user driven knowledge acquisition, and a learning environment which allows for experimentation with the taught material.
The design of the system is based on a domain model of the teaching material, represented as a directed graph of concepts indicating which concepts are preconditions of others. The structure of the hypertext component of the system is based on this network. The network also forms the basis of the student model. This is an overlay model, in which the student’s current understanding is represented as a subset of the domain knowledge. The student model records an integer for each concept within the domain model network which, via the mapping to the hypertext, corresponds to a node.
These integer values are updated by an evaluation module which analyses the student’s problem solving ability within the tutoring component. The tutoring component selects an appropriate teaching strategy based on the values in the student model which constrains the navigation within the hypertext. The student model is the heart of the system.
The various components of the system adapt navigationally and presentationally by comparing the stored integers against threshold levels, which may differ for the various system components. Within the hypermedia component, four states are recognised, allowing nodes to be marked as not ready to be learned, ready to be learned, in work or learned.
Although this simple approach to student modelling allows all the components of the system to access the student model, and so to adapt, it was found that co-ordinating updates from the various components was less successful. It also became apparent that, while the information stored was highly suitable for the tutoring component, it was less so for the others. In particular, the hypertext needed to know how often a particular hypertext page had been presented. A counter in the student model was used to store this information. However as the simple overlay student model in the ISIS-tutor has a single counter for each concept, this value was subsequently over written by other components within the system. This led to the adoption of a more advanced student model which incorporates projections from a central student model for the various components within the system (Brusilovsky 1994b). A projection is created from the central student model by projection rules which present student information in a form necessary for the component to adapt. The central student model stores partly processed information about the student to avoid loss of information that a particular component might need.
Authored by Serengul Smith
E-mail to:
serengul1@mdx.ac.uk
School of Computing Science Middlesex University
Revised: September 1998