A Visual Interactive Tool For the Course “Automata and Formal Languages” Holon Institute of Technology Mark Trakhtenbrot, Vladimir Nodelman, Avi Lamai The Open University of Israel Judith Gal-Ezer, Rina Zviel-Girshin, Michal Armoni, Yahalom Humi

The course Mandatory course for 2 nd year CS students  Studies mathematical models of computation (automata, grammars), their properties and expressive power, transformations, etc.  Provides a strong background for a variety of CS areas: construction of compilers, verification, design of digital systems, etc.

Learning a theoretical CS course is difficult … Why? Heavy use of formal methods:  Intuition behind formal concepts is not always clear  Serious challenge - formal math language to describe abstract objects, their properties and relations  Needed ability of precise math reasoning

Learning a theoretical CS course is difficult … Why? Students’ background and motivation  significant break after the high school; certain erosion in math skills required for CS studies  seeking a high-tech career; tend to view theoretical courses as something not needed for “real work”

More problems… Slow feedback:  Student becomes aware of certain misunderstandings only when getting back the checked assignment  Often happens too late already busy with learning another material

And more … Communication problems:  difficulty to use formal language for asking questions  often not supported technically; leads to a verbal mess In distance education (OpenU):  rare face-to-face classes

As a result…  Concepts remain too abstract  Theorems and algorithms are used improperly  Common problems left without proper attention

The challenge Help to:  make formal concepts more clear and tangible  make communication about them easier  discover problems earlier  get answers in “real time” Use technology to address these issues

To make this happen…  Developed: interactive tool for visual hands-on exploration of the studied computational models  Prototype: - covers automata and grammars chapters of the course - Windows application, downloaded from the course site  Internet version: - so far, automata only

Interactive tool for AFL course Supports the self-study process:  Build-in lessons - based on pre-defined scenarios  Build-in exercises and exams - “american” and “open” questions - automatic check of solutions - tips provided in case of error  Unlimited exercising

Interactive tool for AFL course Major features:  Visual creation of computational models  Static checks of model consistency and completeness  Interactive simulation and animation  Operations on automata and regular languages  Transformations of models  Traceability  Different levels of details

Visual creation of models  Learn basic elements, their properties & relationships  Different views of model (diagrams vs. math notation)

Static checks  Reveal hidden properties; find errors / omissions  Examples: no final states, missing transitions; unused grammar symbols

Simulation and Animation  Models are not just pictures; they are executable  Interactive animation: select next action, observe reaction  Flexibility: one-shot / step-wise; forward / backward; etc. Allows for:  Dynamic check of model correctness run under different test inputs; similar to debugging  Explore different derivation policies (left-most, right-most, use of backtracking)

Transformations and Traceability Variety of transformations supported:  determinization and minimization of automata  translation of grammar into a normal form  conversions: Automata  Regular Expressions Traceability: show mapping between source and target models

Selecting level of details Flexible use of the tool: view all details vs. final result only Example (determinization): for given NDA, build equivalent DA Process:  Build your own solution  Generate final answer with the tool & compare it with yours (e.g. compare simulation results on the same inputs)  Your solution is incorrect, reasons unclear? View all interim details, see what went wrong

Share models to improve communication Attach model file when posting a question / homework Used by recipient both as doc & executable  replaces messy verbal description / makes it more clear  can be checked and run  easier to understand the question and to answer it Similar for assignment solutions published by tutor: view & simulate it to compare with your solution

Summary of learning process improvements Better sense of learned concepts: live & tangible Thorough validation of solutions not just 1-2 paper-and-pencil checks Easy trial-and-error: make changes, check their impact Levels of details leading to proper understanding Improved communication

Further steps Improve integration into the learning process:  Extend the coverage of the course material - developed a script language for definition of lesson scenarios  Assignments with mandatory use of the tools  Levels of access to tool’s functions, according to course schedule  Use of tools in synchronous teaching

Interactive Tools for Teaching Automata and Formal Languages Thanks for your attention