A Visual Interactive ToolFor 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 2nd 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 stepsImprove 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