You are here

Service oriented intelligent tutoring system architecture

21 January, 2016 - 14:46

The service oriented ITS architecture (Lavendelis & Bicans, 2011) consists of two levels,namely the higher and the lower level. At the higher level of the architecture each module contains one or a few main services that are used from the outside of the module. These services implement interfaces of the modules. At the lower level unlimited number of otherservices may be included in each module. These services are used only by the main services of the corresponding module. They are not used from the outside of the module. The service oriented ITS architecture implements the main ideas of the layered architecture described in the previous section. Services of the communication module implement the third layer of the layered architecture. All main services of the remaining three modules (the pedagogical module, the expert module and the student diagnosis module) implement the logical part of the system and thus correspond to the second layer. Lastly, all lower level services implement all particular actions with all repositories and with all fundamental technologies like video streaming. Thus these services implement the interface to the third layer of the layered architecture.

Similarly to traditional ITS architectures the communication module is the only module interacting with the user. It manages the user interface and has to visualize the curriculum, learning materials, problems and feedback. It receives learner’s requests and forwards them to the corresponding services. The module consists of the following higher level services:

  • The main interface service, whose role is to register learner’s actions and forward themto the corresponding services.
  • The main material visualisation service that processes requests to visualize learning materials of different types.
  • The main problem visualisation service that similarly to the main material visualisation service processes requests to visualize problems of different types.
  • The curriculum visualisation service visualizes the curriculum of the course.
  • The feedback visualisation service that has only one function – to give feedback to a learner, when he/she has finished solving the problem or has requested a hint.

To make the architecture open for new types of materials and problems, the communication module contains two types of lower level services that interact only with the corresponding main services. Firstly, the main material visualisation service has one lower level service for each type of materials that is needed to be visualised differently, like video streams and text materials. If new types of materials are introduced in the system, the corresponding lower level service will be added to the module. Secondly, the main problem visualisation service uses the lower level services corresponding to the types of problems used in the system. Thus the main material and problem visualisation services are only mediators – they only have to find appropriate lower level services to visualize materials and problems respectively. Lower level services also have only one task – to visualize the particular type of materials/problems. The higher level services that do not have corresponding lower level services do all tasks by themselves, for example, the curriculum visualisation service is responsible for visualisation of the curriculum. Still, the general architecture can be customized by adding new types of lower level services, if needed. For example, if various types of curriculum are used, corresponding lower level services can be added.The services of the pedagogical module have the same tasks as the module has in the modular architecture. To accomplish them it consists of the following services:

  • The curriculum generation service has to provide the curriculum of the course. It maybe generated automatically by the service or created by the teacher and stored in the database for the service to read from.
  • The main material generation service that is responsible for material generation corresponding to the chosen topic from the curriculum of the course. It uses lower level services capable to generate particular types of materials. Each type of materials supported by the system has corresponding lower level material generation service. For example, separate lower level material generation services can be created for each of the abovementioned different formats of learning materials.
  • The main problem generation service, that is responsible for problem generation.
  • Similarly, to materials, each type of problems has a corresponding lower level service, that generates the corresponding type of problems upon the request of the main service. Such an approach implements similar openness to the multi-agent architecture. The openness of the architecture is further discussed below.
  • The feedback generation service, which is responsible for providing feedback to the learner. It receives the knowledge evaluation and creates meaningful feedback that canvary from comments about answer‘s correctness to detailed explanation of mistakes.

The main material and problem generation services use similar algorithm to carry out interactions during the generation. In fact, majority of the main services use similar algorithm. The following steps are carried out when the main service receives a request to generate a material/problem in the particular topic. The definition of the algorithm will include also actions done by other services to illustrate all interactions:

1. The main service receives generation request.

2. The main service requests student model from the student modelling service described below to know the characteristics of the learner to adapt to.

3. When the main service receives the student model, it queries the service registry to find the corresponding lower level services.

4. If at least one lower level service is found, the request for materials or problems in the certain topic together with needed characteristics is sent to the lower level services.

5. Lower level services create or retrieve from the repository the most suitable materials/problems for the learner’s characteristics in the current topic.

6. The lower level services send their results to the main services.

7. The main service receives responses from all services requested before. If more than one service provides a result, the main services chooses the most appropriate result and forwards it to the main interface service and other main services, if needed.

The expert module contains only one higher level service named main expert service. It is responsible for solving problems given to the learner. Each type of problems has its own second level service that solves the problem. The main service just has to find the correct second level service. The student module contains two higher level services, namely, the main knowledge evaluation service and the main student modelling service. The student modelling service is responsible for collecting information about a learner, his/her actions priorities and knowledge evaluations. It also creates full student model and provides it upon request of other services. The knowledge evaluation service is responsible for evaluating learner’s knowledge level by comparing his/her solution of particular problem to the so called system’s solution provided by the expert agent.

Similarly to the multi-agent architecture, the service oriented architecture is open in thefollowing sense. New types of materials and problems can be added to the system without changing the code of existing services. Only new services corresponding to the new type of problem or material must be added in each component of the architecture where each type of material/problem is handled by separate service. If any new type of materials is added to the system then two services must be added to the system, namely corresponding lower level material generation service and lower level material visualisation serv ice. Four newlower level services must be added to introduce new type of problems. Corresponding problem generation service, expert service, knowledge evaluation service and problem visualisation service must be added to the system. The service orien ted ITS architecture is given in Figure 12.6. Besides the described components the figure contains repositories used to store data, but links among services and repositories are omitted to keep the figure readable. The following repositories can be used in the ITS: the student data repository with personal data and student models, the course repository with data about courses and topics, learning material repository and the problem repository (for details, see (Lavendelis & Bicans, 2011).

The described openness is not the only way to customize the architecture. Specific functionality that does not correspond to any of the traditional modules may be needed, Additional separate modules can be created to include such functionalities. For example, teacher’s interface is needed in any practically used ITS to modify the course by adding, removing and changing topics, learning materials and problems used in the system. Similarly, to the traditional modules additional ones are implemented as sets of services (Lavendelis & Bicans, 2011).

media/image7.png
Figure 12.6 Service oriented ITS architecture