A WEB BASED SOCRATIC TUTOR FOR TREES RECOGNITION Mónica Trella, Ricardo Conejo, Eduardo Guzmán Dpto. Lenguajes y Ciencias de la Computación, E.T.S.I. Informática, Universidad de Málaga, Málaga 29071, Spain.
[email protected]
Abstract. Socratic dialogues has been widely uses as a way of implement an ITS. The idea behind it is that the teaching and learning process should be based upon a personal reflection that can be obtained posing the right question on a guided dialogue. This methodology assumes that the knowledge acquisition is a discovering process in which both the teacher and the student plays an active role. This tutorial strategy has been developed as a part of a web based ITS architecture for declarative domains and it has been applied to the botanical domain. In this paper we describe this component, the knowledge representation that support it and the web interface used
1
Introduction
This work arose as a part of the TREE project ( TRaining of European Environmental trainers and technicians in order to disseminate multinational skills between European countries). The TREE project was included in the EU Leonardo da Vinci Program, and its main goal was the development of an ITS for the classification and identification of different European forestry species. Together with the ITS the TREE project covered the development of a Knowledge Base about the forestry domain [2], an Expert System and an Adaptive Tests Generation System [3]. Each one of these components has an independent Web-based interface that allows the whole system to be used as a learning tool or as an independent consultation tool. The idea of creating a generic ITS architecture for declarative domains arose parallel to the TREE ITS development. This architecture [1], which will be briefly described in the next section, has among other modules a set of tutorial components that are tasks that a student can do to learn something (to read a text, make a summary, take a test...). The goal of this paper is to describe one of those components: the Socratic Tutor. Socratic teaching consists of maintaining a dialogue with the student by asking him/her questions about the subject domain (forestry morphology in the case of the TREE Tutor). If the student fails, the system will infer the possible causes of this wrong answer so it will assist the student in teaching the correct solution by him/herself. Socratic dialogues has been widely uses as a way of implement an ITS. Back in the early days of ITS, the idea of teaching by using a Socratic dialogue was first used by
Collins and Stevens in the classical system WHY [4] and also by Brown and Burton in BLOCK [5]. The idea behind the Socratic dialogue strategy is that the teaching and learning process should be based upon a personal reflection that can be obtained posing the right question on a guided dialogue. The Socratic method assumes that the knowledge acquisition is a discovering process in which both the teacher and the student plays an active role. These features are especially interesting for web-based tutorials because a web session can be conceptually thought as a kind of dialogue. The following dialogue is a very trivial example of this tutorial methodology in the domain of botany. It is supposed to be held between a botany professor and a student during a field visit: S> Could you tell me what is this tree? P> I think you already know it, what do you think it is? S> Isn’t it a birch? P> No, no, this tree has a conic crown and a birch doesn’t. S> All right, I haven’t notice that, so it should be a cypress. P> No, it isn’t it. Have you noted that the arrangement of leaves in this tree is helicoidal and the cypresses have them opposite? S> is that a fir? P> You’re right! It is Abies pinsapo, you may also note that it has cones, dark bark,.... Note that the professor do not give the answer to the student directly, because he thinks it is something that has been explained sometime before, instead of that he poses am initial open question just to know how much the student knows. After the initial answer the professor already knows that the student hasn’t the faintest idea of what it is the tree is. But instead of giving him the answer right away, he gives the student a valuable hint, he points out that the questioned tree has a conic crown, that is something evident, but that has been possibly ignored by the student. He also fails the question, but now the answer can be considered better because both are Gimnospermae. The professor happily impressed by the progress made, gives more data to the student, he indicates the main differences between the cypress and the fir. Finally the student solves the question partially. The professor considers enough the answer and gives to the student the rest of the information. One of the main problems in Socratic tutors has been the knowledge representation. This is, the component that allows the tutor to pose the right question to the student. Most systems deal with non-finite domains, that is, they can not assume that the tutor has all the answer beforehand. They normally use IF-THEN rules and tactical metarules to guide the dialogue and remain it coherent [6]. Another classical problem in Socratic dialogue systems is the natural language interaction [7]. In our case we are dealing with a large (but finite), number of species and with a large (but finite) number of attributes, and we avoid the natural language problem by using a formbased dialogue. The problem that remains is the knowledge representation and the inference mechanism that implements the tutorial strategy. The tutorial knowledge itself has been elicited from heuristic expertise of a human tutor in the domain. In the following section we describe the general architecture in which the Socratic tutor is embedded. After that, the structure and the behavior of the Socratic tutor are described and a brief example is presented.
2
ITS Architecture
During his/her academic life, a student must learn many declarative domains in different knowledge areas as geography, natural sciences, biology, language etc. A generic architecture to build Web based ITSs to teach this sort of domains has been designed (see Figure 1).
Overlay
S TUDENT MODEL Verified Student Model
Estimated Student Model
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DOMAIN KNOWLEDGE CONCEPTUAL MODEL
Expert
Student
...
Experts, teachers, developers
C ONFIGURATION AND DEFINITION
S TUDENT MODEL MANAGER
Expert
LIBRARY OF TUTORIAL COMPONENTS
CONTROL ACCESS / ADMINISTRATION / R EPORTS
I NSTRUCTIONAL P LANNER TUTORIAL STRATEGIES
Student
Fig. 1. Generic ITS architecture for declarative domains.
A more detailed description of its modules and operating way can be found in [1], but in order to place the Socratic Tutor into this architecture a general view of it is given below. In this architecture there are some modules that contain data and knowledge and another functional modules that use this information to carry out their tasks. The firsts ones are: − Conceptual Domain Model, a description of the domain to be teach, − Student Knowledge, a sub-set of the domain model representing what the student knows, − Historical Student Record, that stores all the information of student sessions (number of sessions, session duration, connection address, sessions trace, pages visited, etc.), − Tutorial Strategies, a set of rules and session configuration parameters given by the ITS designer. The functional systems modules are: − Definition and Configuration module, that is formed by a set of tools that allow to the experts and teachers to define the Conceptual Domain Model and the Tutorial Strategies, − Student Model Manager, that actualizes the Student Model depending on the student’s actions results, − Access Control / Administration / Reports, that manages the student system access (login, passwords, the courses that he/she is allowed to connect to, etc.), all the administrative tasks and makes reports about the students, − Instruction Planner, that takes the tutorial decisions during the learning process. It must to decide depending on the Student Model state witch is the next tutorial goal
TEMPORARY STUDENT MODEL
(what domain concepts would the student learn now) and then the best tutorial strategy to teach this to a particular student. The Instruction Planner is the module that bring to the ITS the capability of adapting the learning to each student, − Tutorial Components Library, that implements a set of tasks that a student can do as a part of the tutorial/learning process. All the components have the structure shown in Fig 2. DEVELOPMENT INTERFACE CONTROL
CONTENTS
S TUDENT INTERFACE
Fig. 2. Tutorial Component structure.
The Control is the module in charge of carrying out the component task interacting with the student through the Student Interface using the partial knowledge included by the teachers through the Development Interface. The nature of the Contents module information will depend on the specific component task. For example, a test component will contain questions; a reading-text component will have HTML pages, etc.All components in the Component Library have its own development and student interfaces that are designed to be used through Internet. The instruction is based upon a main cycle that can be repeated: The Instruction Planner first selects a set of concepts to be learned and then it selects the way of teaching them by choosing a Tutorial Component in the Library. When the component is selected, the part of the Student Model related with the tutorial goal designed by the Instruction Planner, is copied to the component Temporary Student Model, that will evolve with the student’s actions. When the student finished his/her task inside the component, the Student Model Manager actualizes the Student Model with the contents of the Temporary Student Model.
3
Socratic Tutor
The Socratic Tutor is a Tutorial Component that teaches by posing a problem to the student and, by maintaining a dialogue, guides him/her towards the correct solution. This component has been designed to teach declarative domains organized hierarchically as for example the botanical domain taxonomy of the TREE ITS (see Figure 4). The Tutorial Components in a tutorial session are selected by the planner based on the current state of the student model. The planner should identify the students needs and configures a partial tutorial goal. Then it selects the most appropriated tutorial strategy to achieve that goal taking into account student’s background. From the Socratic Tutor point of view, the tutorial goal is just to teach the student how to differentiate between two sets of concepts (A and B) of the same level in the hierarchy. Selecting these sets concerns to the Instruction Planner which has access to the global student model
3.1
Operating Schema of the Socratic Tutor
A session with the Socratic Tutor is divided in several proposals. Each of them will finish in a determined state that is stored by the Tutor. Each time a student finishes a proposal, the Tutor analyses his/her trajectory and decides if the session in the Socratic Tutor has to finish or must continue with another proposal. In the section bellow, we have represented a proposal example. The tutorial knowledge that guides the Socratic dialogue of a single proposal is represented by a finite state automaton. The input alphabet of this automaton is taken from student possible answers: − r: right answer, − f : fail, − f+: fail more serious than the previous fail, that is, the fail has been increased, − f-: fail less serious than the previous fail, that is, the fail has been decreased, − f=: fail with the same importance than the previous fail. The system proposal starts in the state 1 asking the student to recognize a concept (what is that...?) by presenting a photo or an image, and progress according to the Figure 3 diagram depending on the student answer. Each proposal finishes with one of the following states: Bi or M, where Bi indicates passing the proposal successfully by doing i fails and M not passing. f+, f=, f-
M
f+, f=, f-
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f= B2 f
1 r
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Fig. 3. State diagram in the Socratic Tutor.
The initial question is reformulated each time that the student fails, including a new hint to help him/her to obtain the right answer. This hint takes into account the wrong answer given. The proposal continues until the student finds out the right answer or the instruction is considered unfruitful.
The system gives more opportunities and help to the student that is decreasing his/her fails because that means that the student is improving with the Tutor hints, so is probably that he/she reaches the right solution. Whereas if the student increase his/her fails the system detects that the student is not learning and must give him/her the opportunity to start another proposal at which he/she would learn better. Two criterions have been established to classify the student’s error into f +, f-, or f=: 1. The main goal of a Socratic Tutor proposal is that the student differentiates between sets of concepts (of the same level in the hierarchy): A and B. C represents the rest of concepts in the knowledge base. So the first criterion to classify the error is the set to which the students answer belongs to. Let us suppose that the proposal concept is Aj ∈ A . Then the possible wrong fails ordered from greater to minor are: Bi ∈ B, Ci ∈ C and Ai ∈ A. 2. The second criterion of error classification is the domain hierarchy. A student error will decrease if the hierarchy level of the first predecessor non-coincident of the proposal and student response is lower than the one in the previous error. (It is not the same to confuse one concept with another with the same parent in the hierarchy that to confuse it with another that has a completely different predecessor.) A proposal starts when the system presents to the student a photo or an image of one element of the input sets. From that moment, the Tutor analyzes the student answers and acts in consequence. The Tutor has some tasks that are common to all the states represented in the Figure 3: 1. Finding non-coincident predecessors of the proposal and the student answer. 2. Extracting the list of differences to be presented to the student as a hint. 3. Finding two photos or images that show as many differences of the list as possible. 4. If there are some features in the list of differences that can not be shown, the Tutor will remove them from the list. The amount of help is increased each time a student makes an error. As the tutorial goal is learning to distinguish two set elements, the hints given to students are the list of differences between the right answer and the student answer. The differences are classified in two categories: the important differences (those that are necessaries to differentiate two concepts, clearly observable and substantially significant); and the additional differences (those that are not key features in order to distinguish them but can help in this task). The hints presented to the student start with the important differences of the higher pair of nodes non-coincident in the hierarchy and advance in two ways: first going down in the hierarchy and then adding additional differences to the list. 3.2
Tutor sessions
A session is composed by several proposals. Each proposal presents to the student a concept of any set of the tutorial goal (Ai ∈ A or Bi ∈ B). During a session the same proposal will be presented to he student in order to confirm the previous results. The session finalization criterion will be maximum numbers of proposals for any possible finalization state ( M or Bi). These factors will be configurable by the teachers and are the following: − Maximum number total of proposal presented to the student.
− Maximum number of consecutive proposals finished in the state M. − Maximum number of consecutive proposals finished in the state B0. − Maximum number of equals proposals (about the same domain concept) finished in the state Bi (i > 0). The finalization criterion is local to the Socratic Tutor, which is just a component of a complex system. The role of the finalization criterion is to decide whether or not this instruction is being useful to the student. In the worst case, the objective previously decided by the Instruction Planner might be too difficult, or perhaps the teaching style is not well suited for him. The Socratic Tutor estimates the fulfillment of the goal and passes this information to the Student Model Manager that modifies the Global Student Model and lets the Instruction Planner to act accordingly. The next task proposed to the student may be any other component of the system.
4
Proposal Example
In what follows we will use the TREE tutor and its hierarchically structured domain as an example, in order to make the explanations clearer. The forestry species domain is structured hierarchically in several levels: divisions, classes, families, genera, and species. We have developed a knowledge acquisition tool for domain experts to complete the domain Knowledge Base (KB) through a webinterface [2]. Fig. 4. shows a partial view of the domain hierarchical structure. Each node in the hierarchy has its own set of attributes that describes it.
Abies
Gymnospermae
Angiospermae
Divisions
PINACEAE
BETULACEAE
Families
Betula
Genders
Tsuga
Picea
Larix
Cedrus
Abies lasiocarpa Tsuga canadensis Picea asperata Larix eurolepis Cedrus libani Abies nebrodensis Picea engelmannii Larix russica Abies pinsapo Picea mariana Picea orientalis Picea rubens
Pinus Pinus aristata Pinus banksiana Pinus brutia Pinus canariensis Pinus halepensis Pinus jeffreyi Pinus nigra dalmatica Pinus nigra salzmannii Pinus peuce Pinus pinaster Pinus pinaster atlantica Pinus pinea Pinus ponderosa Pinus sabiniana Pinus sibirica Pinus sylvestris Pinus sylvestris rigensis Pinus uncinata
Alnus
Betula pendula Alnus glutinosa Betula pubescens Alnus incana Alnus cordata
Species
Fig. 4. Partial taxonomy of the TREE KB
In the example of the forestry domain, we can say that a student has learned the European trees if he is able to recognize any given specie from a set of photographs. In order to help in this task, the Domain Model contains the main differences and
similarities between the nodes in the hierarchy. All the differences are extracted automatically of the KB and the botanical experts mark those that are more helpful to differentiate two species. To complete the Domain Model there are a set of photographs that are introduced by experts through the Web interface. Each photo has associated information about what is pictured in it. A session with the Socratic Tutor is divided in several proposals. In order to explain the interaction between the system and the student, we are going to develop a tutorial proposal example with the Socratic Tutor. Let us suppose that the tutorial goal is that the student distinguishes the sets of genera A ={Abies} and B={Betula}. The partial taxonomy corresponding to those genera is shown in the Figure 4. The goal of this tutor is to teach by practicing with photos. The system will show a photo to the student and he/she will have to classify the genera in the photo.
Fig. 5. Example of a proposal
In the example in the Fig. 5, the Tutor asks the student for the genera Abies and he/she answers Betula. The first time the student fails (state 2 in Fig. 3), the Tutor looks for the first non-coincident predecessors between the proposal and the answer, and makes the list of important differences between both. In the example, the non-coincident predecessors of the pair Abies-Betula (proposal-student answer) are divisions, Gimnospermae-Angiospermae and families, Pinaceae-Betulaceae (see Fig. 4). So the system presents to the student the main differences between the divisions (first noncoincident predecessors) Gimnospermae and Angiospermae (see table 1). The next student answer is Cupressus and the system must determine if the student fail has been increased or decreased with regard to the previous error. The first criterion was the set to which the students answer belongs to. Both fails are genera of the same set (C = {All the genera in the KB} – A – B), so the system analyzes the second criterion: the domain hierarchy. In the first fail, the genera Abies and Betula are from a different division. In the next fail the genera Abies and Cuppressus are from the same division (Gimnospermae) but from different families (Pinaceae and Cuppresaceae respectively), so the system concludes that the fail has been decreased. The next system action is to decide the hints to be presented and go to the state 4. The hints advance in two ways during the proposal: first going down in the hierarchy and then adding additional differences to the list. As the hierarchy level of the fail has changed the system presents to the student the main differences between the families Pinaceae and Cuppresaceae. The next answer is correct so the system progress to the final state B2. If the student would answer another Cuppressus species instead of giving the correct answer, the system would present the additional differences between the families Cuppresaceae and Pinaceae. If the student makes the same mistake again, the system would present the main differences between the genera Abies and Cupressus. IMPORTANT DIFFERENCES IT HAS FRUIT OR HAS NOT REAL FRUIT It has cone, strobilus or aril
It has real fruit CROWN TYPE
Conic crown
Without a characteristic form FLOWER’S PERIANTH
Flower without perianth
Flower with petaloid perianth
Flower with sepaloid perianth Flower with calyx and with corolla ADDITIONAL DIFFERENCES APPEARENCE OF FLOWERS Not apparent flowers, hardly visible Apparent flowers, easily visible
Table 1. Differences between Gimnospermae and Angiospermae IMPORTANT DIFFERENCES FLOWER’S PERIANTH Helicoidal
Opposite Verticillate
Table 2. Differences between Pinaceae and Cuppresaceae
5
Conclusions
There are several tasks that have to be done as a part of an instructional process. The instruction over the Internet requires that all of these tasks would have a web interface. We can benefit from the web structure if we could design each component separately. To make it possible a new architecture has been proposed. This architecture is modular and has a library of tutorial components that can be generic (used for any domain as for example test component, reading-text component...) or designed specifically for a particular domain. In this paper we have described one of these particular components: the Socratic Tutor. This component is based on the Socratic methodology where the teaching and learning process are based upon the personal reflection that can be obtained posing the right question on a guided dialogue. A finite state automaton conducts the Socratic dialogue. This tactical knowledge representation can be easily defined and/or redefined by the human domain experts. This component have been developed for the TREE ITS, that teaches to recognize different European forestry species. The morphological botanical domain is a hierarchically structured domain, the Socratic component can be reused for domains of similar features. The Socratic Tutor has been completely designed and now we are taking care of the implementation phase. New research lines are open to study the impact that this dialogue has on the student general performance, and to automatic learn while teaching what are the hits that better solve the student impasse.
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