Abstract
In the process of developing an Intelligent Tutoring System (ITS), the construction of learning material to be considered in the teaching of a given domain is a crucial stage. Some of these materials are in hypermedia form. The main object of this paper is to show that HTML documents can be used as pedagogical material under the control of an ITS. A Web browser is used as the medium for the delivery of tests and the teaching of verbal information (declarative knowledge). We also show how to encapsulate a Web browser in order to use it under the control of the ITS. The language used is Smalltalk.
Introduction
The use of hypermedia resources in learning and teaching becomes increasingly ineluctable. This interest was facilitated by the arrival of the WWW (World Wide Web) which offers the possibility to access hypermedia resources available on the Internet. Some problems related to the monitoring and the control, by the system, of the student learning process present themselves. For example, the student can very well exit the framework of the course during its navigation on the net and go out to other resources of the Internet, not under the tutorial system control. In an intelligent tutorial system (ITS) it is important and even indispensable to be aware of the learning activities and actions of the student; the analysis of the reasoning process of the student depends very much upon this knowledge. The main problem here is the management of the teaching/learning process by the ITS. This paper shows that HTML documents can be used as pedagogical material under the control of an ITS using a Web browser (here Netscape) as an interface. The first step of this study was to develop a system for the generation of tests on the World Wide Web in an ITS setting for teaching the Québec road regulations [1] . The second step concerns the use of such resources by an ITS. This requires the monitoring of the student while he is using a Web browser [2] and communications (data exchange) must be established between the ITS and the Web client. The other modules of this ITS have been developed in the SAFARI project. The SAFARI project goals are the construction of simulationbased ITSs for training and the development of a methodology to sustain such a construction [3] .
In order to exploit in an ITS all the facilities offered by the Web, it is important to settle the problems related to the construction of pedagogical resources and the manner in which they will be presented through the Web. Researchers have shown that the implementation of pedagogical resources in the form of hypermedia can improve the learning of cognitive skills for some students [4, 5] . Since some concepts from the application domain we have chosen are essentially visual (road signs, marks on the pavement, etc.), the use of hypermedia is particularly useful. However, one cannot hope that the student will learn simply by putting a set of hypermedia resources at their disposal [6] , it is important to manage their use by the student. In this paper we consider the following aspects:
• The use of a WWW client (in this case, Netscape) as the interface for the presentation by the ITS of verbal information (declarative knowledge) [7] , tests, exercises and problems, • the capture in real time and analysis of the student's trace (the sequence of actions carried out by the student while interacting with the Web pages), • the use of a student model, • control over the WWW client during the teaching/learning process, • the communication between the WWW pedagogical resource and the ITS.
In order to carry out these objectives, a structured representation of the subject matter the ITS was to teach was proposed that took into account pedagogical resources of type hypermedia, and was able to exploit them in a hypermedia environment [8] . The model is essentially object oriented, and permits one to see a pedagogical resource as an object whose private state varies according to its nature, and that offers an interface allowing communication with other components of the ITS by message sending.
After a brief presentation of the architecture of the overall system there follows a description of the different types of pedagogical resources that have been retained (at the current time) for exploitation on the WWW and the way in which those resources have been implemented. Finally, an account of how the Netscape Web browser was encapsulated (transformed into a Smalltalk object) is presented with illustrations of the use of such resources in an ITS by examples drawn from a course on the Québec road regulations.
ITS architecture
In this section a summary description of the system architecture of our ITS is presented. The tutorial system is composed of three main components: the Curriculum component, the Planner and the Tutor (Fig. 1 ).
Curriculum component
This component [9] is comprised of two parts: the first is composed of one or many objects that are instances of the class curriculum (each curriculum describes a subject from a domain, pedagogical and didactical point of view) and the second is an object of the class course. A choice of several courses can be offered to the learner, nevertheless we place ourselves in the situation where the learner has already chosen a course. The attributes of a course (e.g. its summary and its requirements) determine the intentions of the course builder (teaching aims), independently of a particular student using the ITS. The initial requirements of a course allow the target audience to be set. The identification of such an audience helps the instructional designer to construct the curriculum. A test is administered by the ITS to each student about to start the course to ascertain whether or not essential background information is known. If not, the student must acquire this knowledge before starting the course. Of course, if the curriculum is sufficiently complete the ITS could itself teach the missing preliminaries.
A modelling approach called CREAM (Curriculum REpresentation and Acquisition Model) has been proposed for curriculum representation in an ITS. In this model, a curriculum is a structured representation of the subject matter in terms of capabilities [7] (see below), instructional objectives and pedagogical resources (learning materials). Achievement of instructional objectives contributes to the acquisition of capabilities. This achievement is supported by pedagogical resources through learning activities (exercises, demonstrations, problems, simulations, etc.). CREAM implements domain, pedagogical and didactic aspects of a subject through a network organization of capabilities, of instructional objectives defined on these capabilities and of pedagogical resources supporting the accomplishment of instructional objectives. Using these three knowledge structures, we construct a curriculum knowledge transition model that contains particular links between their elements.
The capability model.
A capability is a knowledge (or cognitive) unit stored in a person's long term memory that allows him to succeed in the realization of physical, intellectual or professional activity. When we want to represent this kind of curricular knowledge, we ask ourselves what must be taught, that is the content we want the student to acquire. Three categories of capabilities are set up in CREAM: verbal information, intellectual skills (discriminations, concepts and rules) and cognitive strategies. The capability model (CREAM-C) is a multi-graph where nodes are capabilities (each type of node denotes a capability category) and links among them can be of several types: analogy, generalization-specialization, abstraction, aggregation, deviation.
Instructional-objective model.
An instructional objective is the description of the behaviour (or performance) that the student must demonstrate after a learning process. Several studies have shown the necessity of objective specification in teaching systems [10, 11] . This has been taken into account in our representation approach by introducing an instructional objective model (CREAM-O) in which instructional objectives are represented and organized together by links of type prerequisite, complementary or pretext. These links can be defined by the instructional designer or generated by the curricular system by reasoning on its knowledge structures [9] .
Learning resource modelling.
Pedagogical resources are the means used by the teaching system to support the teaching/learning process. Several categories of resources are considered in CREAM: those that support the teaching/learning process for the acquisition of knowledge (problems, demonstrations, exercises, hypermedia document, etc.), the expert type resources that act as experts that can intervene in the teaching/ learning process to help or criticise the student in a specific activity (advisor, criticizing systems, coach) and physical and media resources that represent basic teaching material (simulators, video, sound, pictures, etc.). We have identified several types of links between resources: equivalence, abstraction, case of, use of, and auxiliary. The network defined by these relations represents the resource model (CREAM-R).
CKTN:
Coupling the preceding models. The coupling of the preceding models creates special links between their elements. In the space resulting from this coupling, we group each objective together with its associated resources in an element we call a transition. The input capabilities of a transition are those that are prerequisites to the achievement of the objective involved in this transition. The output capabilities of a transition are those that are produced by the achievement of the objective involved in the transition. Thus, they produce two types of links between capabilities and objectives: prerequisites and contribution links. The resulting network is called CKTN (Curriculum Knowledge Transition Network). Figure 2 shows part of the CKTN in the Baxter pump manipulation domain. A prerequisite link from a capability C to an objective O expresses the fact that C is a precondition to the realization of O. A prerequisite link is characterized by its nature (mandatory, optional) and by the minimum mastery level required on the source capability to be able to consider it sufficient for overstepping the link (entry level) and thus be able to eventually realize the objective. This entry level is specified by using a qualifying value taken from an evaluation (or acquisition) vocabulary. For example, in Klausmeier's vocabulary [12] , a capability of type 'concept' can be recognized, identified, classified or generalized (four acquisition levels) whereas a capability 'rule' can be applied or transferred (only 2). Evaluation vocabularies are denoted in our system by an ordered set of integers representing different levels of acquisition. Since several vocabularies exist for describing the same type of capability, the designer must choose a vocabulary before proceeding to the construction.
A contribution link qualifies the way in which the realization of an objective contributes to the acquisition of a capability: it can be a strong, moderate or weak contribution. Therefore, several objectives can contribute to the acquisition of one capability. 
The planner
This subsystem uses the course specification and takes into account the learner, as perceived through the portion of the student model that concerns the subject matter (objectives and pedagogical resources available), this subsystem elaborates dynamically the plan for the course. It is in part in this dynamic elaboration of the course that the ITS shows pedagogical competence. There will be re-planning whenever the tutor subsystem considers that the learning is less than adequate. The planner proposes teaching tasks (to motivate the student, to recall previous knowledge, to formulate an objective, to present content, to assess the student, etc.) for the tutor to realize. The planner is responsible of the global aspects of individualized teaching.
Tutor
This subsystem manages the interactions with the learner, realizes the teaching tasks by choosing and using pedagogical resources (teaching material), controls the teaching process and the dialogue with the student, according to the selected tutoring mode (coaching, criticizing, etc.) replies to remediation needs and to help requests from the student, updates the student model, etc. The tutor is responsible for the interactions with the learner and the local control on the teaching process.
WWW pedagogical resource
We define pedagogical resources as the means (exercises, problems, tests, simulations, demonstration, video, etc.) used by the teaching system to support the student's learning of the capabilities described by objectives. They can also be used to practice or reinforce capabilities that have already been acquired [13] .
Learning material type
We have produced a taxonomy of pedagogical resources. This taxonomy makes several categories of resources stand out ( Fig. 3 ):
• Those that support the learning/teaching process (problems, demonstrations, exercises, hypermedia document), • The expert type resources (advisor, critiquing systems, coach) that work as experts that can intervene in the learning/teaching process to help or to criticise the student in a specific activity, • Physical and media resources (simulations, video, sound, pictures, etc.).
We have mentioned only the main categories of resources, others can be identified. Figure 4 shows the hierarchy (partial) of pedagogical resources we consider. In this paper we consider only those pedagogical resources which are exploitable on the Web.
Learning material modelling
In the proposed model, pedagogical resources can be associated with instructional objective to support its acquisition (see Section 2.1). They can also be associated with capabilities [7] . For example, an HTML resource can be associated to a verbal information to present it. A test can be associated to a concept to allow the assessment of the acquisition of that concept at a time selected by the tutor.
This type of test can be generated automatically by using examples, non-examples and neighbour concepts associated to the concept. If the system decides to assess the acquisition of a concept, it sends a message to an instance of the right class of tests. Figure 5 shows a subset of the protocol for some of the classes shown in Fig. 4 .
In the learning/teaching process, the teaching itself is done at the level of pedagogical resources. However this activity can be decided by the student or by the system according to the tutoring mode chosen. When the system is in charge, the tutor has to decide which pedagogical resource to put into play (a demonstration, a problem to solve, a test on the acquisition of a concept, content to read, etc.) by taking into account the evolution of the student and the student model. Once an activity is chosen, the tutor sends the message to it to present itself. As an example, if the resource is a test of type hypermedia then a WWW client is going to show up in the interface, displaying the test and ready for the student to work on the test.
Example: creating and displaying a simple identification test on the indication sign |x| x := SimpleIdentificationTest generate: #('indication' 5 'toto'). "x contain an instance of SimpleIdentificationTest on the indication sign concept" x present "load x in a Web-browser"
Creation of WWW resources
We focused on two types of HTML document: those that are used for the presentation of a course content, and those that are used for the evaluation of a student knowledge about the domain. Returns the result and the details of the student performance. result Analyzes the student performance and returns a value between (success, fair, fail) according to the test inputs (will be specialize in the subclass).
HTMLDocument Class
PedagogicalResource Class HTMLTest Class Figure 5 . Protocols of some resource classes.
Explicit creation of content presentation document.
We have been inspired essentially by the domain analysis undertaken in the SAFARI project. This suitable analysis emerge some number of knowledge (concepts, rules and verbal information) involved in the domain (here the Québec traffic highway code). Instructional objectives are defined on these knowledge and resources are connected to them. For example, HTML documents have been built to support the teaching of roads signs. These documents content images corresponding to different signs and some textual explanations. Some resources like videos, simulations and animations are connected to objectives that deal with procedural knowledge. HTML documents that are used in our ITS to the content presentation are explicitly created by using the HTML syntax. The granularity of each document depends on the way involved capabilities are connected together. Links between capabilities serve to guide the exploitation of the document by a given student during the teaching-learning process.
Dynamic generation of evaluation resources.
Taking into consideration an instructional objective, there exists a multitude of evaluation resources that can measure its achievement. These evaluation resources can be of several types; true-false test, multiple choice question, sentence to be completed, etc. Also, when the evaluation focuses on the acquisition of a concept, particular tests allowing to measure its acquisition by the learner, can be generated automatically from the concept structure. The dynamic test generation presents some advantages:
• The gain of memory place: it is no longer necessary to produce all possible tests and to store them before presenting them to the student; • The variety of tests: the dynamic generation offers to the teaching system the possibility to vary the content of the test as well as the object of the test in the margin of choice covered by the subject-matter. The test generation process consists of considering the concept on which we want the system to test the student and to use examples, non-examples and nearmisses associated to this concept (according to the curriculum structure) to built a test in the form of an HTML form. Figure 6 shows components of the test generation system. 
Test presentation through the Web
Tests present themselves as interactive HTML documents (HTML forms) (Fig. 7) . This allows the student to enter answers, which can be sent to a server computer and processed by a program on the server. The treatment of student answers to an HTML document is made possible by the common gateway interface (CGI) mechanism [14, 15] .
This mechanism makes possible the execution on the server of a script or a program with parameter values provided by the student. It can accept data entered by the user on the client side and generate an HTML document interactively (Fig. 8 ). An HTML form provides a simple way to collect data from the user on the Web. Student results on a test can be captured and put at the disposal of the tutorial system (in tutorial mode) or treated by a program and be returned as a WWW page to the student. Such a page could contain an indication of the student performance.
Navigation trace: analysis and intervention
How to monitor the student once they have been given access to the WWW? The approach taken was to use the history file automatically generated by Netscape. By the use of a demon, the tutorial system can check the content of that file in order to know what hypermedia links are followed by the student. Every instance of a hypermedia resource contains a list of the anchors present in the document, so the system can know whether the student was working within the planned pedagogical resource or followed a link out of part of the Web under the tutorial system's control. The system can regain control on the session if it so desires. 
WWW

Encapsulation of the Netscape browser
In the learning/teaching process, some activities do not necessitate the utilization of the Netscape browser. It is therefore important to manage its presence in the learning interface. To achieve that, we have decided to make a Smalltalk object out of the Web browser [ Fig. 9(a) ]. [ Fig. 9(b) ] shows part of a WWW object protocol.
The tutor can ask a Netscape browser (instance of the class W3-Client) to put itself in the background simply by sending it the message hide. The message show brings back the browser. Thus the Web browser is under the complete control of the tutorial system and is only available when needed.
Conclusion
We have presented an approach of the exploitation of the WWW documents by an ITS. Several aspects have been explored:
• the presentation of an architecture including a curriculum and a course specification, • the automatic generation and the presentation of tests, • the capture of the test results and its availability to the ITS for further treatment, • the capture of the navigation trace of the student, • some aspects of the communication between the ITS and the WWW browser.
The application on which this approach has been built is available on the Internet, and the URL is http:// www.iro.umontreal.ca/ people/ nkambou/ menu.html. The arrival of languages such as Java [16, 17] and of Java enabled browsers brings new solutions to problems related to the interactivity of WWW pedagogical resources and to their distribution on a network.

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