Re-engineering a Computer-Based Learning Course in Digital Electronics for Flexibility, Re-use and Network Delivery Domenico Ponta and Giorgio Da Bormida Department of Biophysical and Electronic Engineering, University of Genoa Via Opera Pia 11A I-16145 Genoa - Italy Phone +39-10-3532759 / 174, fax +39-10-3532175 E-mail
[email protected],
[email protected]
Abstract Computer-Based Learning and Computer Networking can cooperate in providing a flexible and cost-effective approach to of engineering education problems. Our work presents a methodology for reengineering material originally developed for standalone use in view of two requirements. The first is to allow the re-use of the same material for different pedagogical scenarios. The second is to make the courseware suitable for delivery in a computer network, optimizing telematics resources use. In the paper we discuss restructuring criteria, showing their practical application in our courseware for Digital Electronics.
Courseware for Electronics: Methodology Our group at the Department of Electronics Engineering has been working on the production of Computer-Based Learning (CBL) material for Electronics Engineering, specifically targeted to introductory courses on Analog and Digital Electronics. Our existing material is composed by a wide collection of learning modules, connected by a system of links, whose nature and structure are different accordingly to their function. The first layer of the courseware is implemented in Asymetrix ToolBook. Hypertextual expositive material includes animation and pedagogical simulation to provide an intuitive idea of a concept, together with or instead of a textual explanation. Verification features, usually as multiple-choice questionnaires, are scattered through the course. Interactive learning tools, designed to enhance understanding, belong to this layer [1]. Introduction to real design issues is achieved in the second layer, where general-purpose simulators allow the learner to test simple digital systems and algorithms of her/his own design [2]. They are applications, custombuilt with high level languages, with a strong pedagogical orientation, intended also to introduce the student to the use of professional CAD tools.
Courseware Restructuring for Flexibility and Re-use: Pedagogical Documents One of the targets of our work is to restructure existing material to allow its re-use for different courses, curricula and teachers. In fact, the basic concepts of digital electronics are part of all engineering curricula but demand a different pedagogical approach according to the specific context. For instance, non-electrical environments need a conceptual background on digital systems, but do not require design skills, while computer science may want to practice design and play down electrical parameters of logic devices. This work is part of our activity in the project ARIADNE [3] and we use, for coherence, its terminology. To allow re-use, the learning material needs to be segmented: we define a “Pedagogical Document” (PD) as a logically indivisible segment of courseware, represented by a file or a set of files, that introduces some kind of knowledge. For example in our case (Digital Electronics) a PD may be a theorem, a series of definitions, a pedagogical animation or simulation, a worked example. Proper combinations of PD’s may produce different courses ranging from simple hands-on sessions on logical gates behavior, all the way to a formal treatment of Boolean algebra. The main issues related to PD’s construction are: content, granularity and linking. As far as content is concerned, the general definition of PD given above it is not always easy to apply because the identification of isolated units of knowledge in the original continuos stream of courseware is somewhat arbitrary. In practice, segmentation is carried on using as a guide the teacher’s pedagogical experience and thinking to possible re-use scenarios (Figure 1). The term granularity refers to the average file size of segmented material. Per se, this parameter is not relevant for the definition of the PD, that deals only with the content, as it will be shown in the following. File size, though, must be taken into consideration for practical reasons. Fine granularity increases total courseware memory occupation because each PD must replicate features that were common before segmentation, such as backgrounds and book scripts. In the course of our work we have noticed that, dealing with ToolBook
files (in the following called TBK), the highest subdivision level we have experimented with, i.e. single page PD (the basic building block of ToolBook documents), practically doubles overall size. Also, small PD’s obviously increase the courseware flexibility, at the cost of a more complex linking system. After segmentation, the CBL material becomes a heterogeneous set of PD’s that are not interconnected. At this point each PD is independent from the others and completely re-usable. Only a subset of links is still valid: these are called “internal” links because each of them points within its own PD. The problem is the reinstatement of “external” links, that are critical features for courseware flexibility, without modifying the PD’s to guarantee their re-usability. This problem is approached in a general way in the framework of the ARIADNE project [4], where a specific tools assembling together pedagogical documents into courses and curricula and presenting them to students, are being implemented.
Existing CBL material
Scenario A
Scenario B
Scenario C
Pedagogical Documents (unused-used)
Figure 1. Re-use of segmented material for different pedagogical scenarios.
Courseware Delivery on Network The second target of the work is to make the learning material suitable for delivery in a computer network, where a different organization is necessary to optimize network resources. Adaptation of CBL material for the network could be done using different strategies. In our case, it takes advantage of the methodology outlined in the previous section. Ideally, network delivery would imply on-line courseware consultation, reducing to a minimum the
storage necessity at student’s end and taking maximum advantage of a network server as a controlled and always up-to-date repository of all the courseware. The local situation of networking services does not allow a full implementation of this feature, for two orders of reasons: data transfer limitations and lack of proper courseware. On-line execution is not always feasible for material developed for stand-alone usage. An obvious solution is the use of Internet File Transfer Protocol (FTP) to download educational material for off-line use. Stand alone use of learning material is, anyway, a mode of operation that reduces connection costs and it is most suitable for frequently consulted material. Another possibility is the transformation of courseware expositive documents into HTML documents, gaining the advantage of on-line consultation, but losing all the features that go beyond simple hypertext, such as animation and local simulation. Still another solution is to use a Web browser, Netscape Navigator, for the delivery of ToolBook documents, configuring the browser to handle TBK files. The Web-based distribution of ToolBook documents, that contain multiple links, is not automatic, because the last version of ToolBook needs to have all the files available on the local machine. For this reason we have developed a Dynamic Link Library (NeTbk.dll) to interface ToolBook and Netscape, exploiting the Dynamic Data Exchange (DDE) support features of both. NeTbk.dll implements both a DDE server and client in order to allow ToolBook and Netscape to fully control each other and, in particular, to transparently download TBK files when needed. The system is configured to automatically save in a local directory a copy of the files that have been used, in order to access them remotely only once and rebuild step-by-step a personal copy of the courseware [5].
An Example: Restructuring the Courseware Section on Finite State Machine This section gives an application of the guidelines just exposed using as an example the work that is actually in progress to re-organize the existing courseware of the course Digital Systems Electronics (ESD). While all course material is being reworked; we choose to present the section dedicated to sequential digital networks and Finite State Machine (FSM) synthesis (Figure 2). The existing CBL material is based, as contents are concerned, on the course syllabus prepared by the teacher, but its organization is not exactly the same, because the hypertextual structure offers many alternatives to the traditional text organization. Because the hypertext is based on Asymetrix ToolBook, the minimum structure of a unit of courseware is the “page”. This, though, is not the same as a printed one, because a single ToolBook page may include a large number of expansion buttons, each of whose provides a
further explanation. The page may also include animation and, therefore, enrich its content without adding to the page number. In the original material, the purpose of the first layer is to deliver the expositive and demonstrative parts of the course, such as text, expansions, animation, local simulations. All these features are embedded in TBK files. Each file contains its own index, that allows the user to reach subjects with a granularity similar to the one of the printed notes. When the courseware is used on network, one immediately realizes that the overhead associated with running TBK files from the browser is not justified, when the special features provided by ToolBook are not needed. This may be the case when the information is made of text and images only. A HTML file may provide
Level 1 (Section)
Boolean algebra and logic circuits
Level 2 (Chapter)
Level 3 (Sub-chapter)
Methodology implemented
Electrical param. of logic devices
ASM charts
K-maps from ASM chart
Expositive
a more effective structure for simple consultation, while TBK-based PD’s may be linked when interactive explanations are required. The combination of HTML and TBK files is therefore an interesting solution, because allows a very convenient network access, while providing to the learner the option of obtaining a pedagogical information from TBK files linked to HTML. Such approach has been applied to the presentation of a large repository of exercises and problems, developed over the years as written tests for final examination. In our example, we take into consideration those dedicated to the practice of FSM-related issues (Figure 3). A typical problem ask for the design of a digital system composed of standard blocks like registers and counters, controlled by a FSM, to perform a specific function.
Standard comb. logic devices
Synthesis of synchronous state machines
Interactive synthesis
HTML-based index
State assignment
Animation of ASM charts
Interactive
Finite state machine
MCQ Simple exerc.
Verification
Single chapter download
FSM Simulator
On-line consultation
Practice
Figure 2. Structure of the section on FSM: Pedagogical Documents are placed at level three.
The tree structure present, after a table of content classifying the problems into overlapping categories, another HTML layer containing the text of each exercise. A further layer provides guidelines, hints and different sample solutions, presented as formatted text and figures. At this point, the learner that needs more information or special help in understanding a particular solution, has the option to access the TBK layer underneath. This last layer has been the object of an intense activity, developed in cooperation with the best students of the course [6], to identify methods fostering understanding of the basic issues of FSM-based digital design. Essentially we have approached the problems
under three different views: • presentation of a solution, explained step-by-step through pop-up windows associated to ASM chart states and hardware components; • interactive workshop guiding the learner to reconstruct a solution by the selection of different alternative steps. Wrong choices are explained; • interactive simulation of the digital system presented as solution. Its behavior can be analyzed as FSM state evolution, time-domain waveforms and logical values of signals. In the final phase of training, learners use general purpose tools to simulate a digital systems of their own
design. In the section of the course that has been used as example the most important is a FSM simulator (SIMFSM), that is described in more details in these same proceedings [7]. The simulator is a Windows application programmed in Microsoft Visual Basic and consisting in a quite large EXE, one DLL and a HLP file obviously joined together in a single PD. Its current software structure does not allow on-line execution, and the only choice is downloading the files from the network server for a permanent installation on the client machine. Nevertheless, the possibility to create a large repository of network-accessible SIMFSM input files looks interesting, because it provides a large pool of FSM examples to be used for training. Students may even be encouraged to add to such repository with their own works. We are working on a new release of SIMFSM programmed in Java to allow multi-platform on-line execution.
Solved Problems Repository FSM
Other
Problem X
Hints & Sol. 1
Microproc.
Problem Y
Hints & Sol. 2
On-line consultation
Exercise simulation
Exercise simulation
Exercise simulation
HTML and images files (GIF) ToolBook files (TBK)
Figure 3. A combined HTML-TBK structure is used for the consultation of sample problems solutions. After segmentation, the CBL material cannot be used directly by students as it was before, because of the lack of a formative path. It’s therefore necessary to make segmentation transparent to final users: they should not notice a loss of continuity between the different components of the courseware, while they should appreciate the improved overall performances for on-line
consultation. In our preliminary experiment, while waiting for the general tools to be provided by ARIADNE, we have delegate their functions to a threelevels HTML-based indexing structure. For the smaller documents, we have reconstructed only links for sequential navigation, to avoid too frequent returns to index.
References 1. Ponta, D., Parodi, G. and Donzellini, G., “Practical electronics taught by hypertext: the WORKBENCH project”, Computers Education, Vol. 16, No. 1, pp. 127-132, 1991. 2. Ponta, D. and Donzellini, G., “Learning Electronics with Hypermedia and Computer Tools”, proceedings of CALISCE ‘94, International Conference on Computer Aided Learning and Instruction in Science and Engineering, J. Dessalles editor, Paris (France), 1994. 3. Forte, E., “CAL, Distance Learning and Telematics: Pipes, Contents or Structure?”, proceedings of CAEE ‘95, International Conference on Computer Aided Engineering Education, J. Breza editor, Bratislava (Slovakia), 1995. 4. Project ARIADNE Programme: Alliance of Remote Instructional Authoring and Distribution Networks for Europe (ET 1002, European Union, DG XIII, 4FWRP, Telematics for Education and Training), 1996. 5. Parodi, G., Ponta, D., Scapolla, A.M. and Taini, M., “Internet-based Cooperative and Distance Learning in Electronics”, proceedings of CALISCE ‘96, International Conference on Computer Aided Learning and Instruction in Science and Engineering, San Sebastian (Spain), 1996. 6. Da Bormida, G., Ponta, D. and Donzellini, G., “Teacher-learners cooperation produces an innovative computer-based course”, proceedings of ED-MEDIA 96, AACE Eighth World Conference on Educational Multimedia and Hypermedia, Boston (USA), 1996. 7. Ponta, D. and Donzellini, G., “A Simulator to Train for Finite State Machine Design”, proceedings of FIE ‘96, Frontiers in Education Conference, Salt Lake City (USA), 1996.
