Vending Machine FSM Benjamin Welton 03/20/2010 CS 480

Overview System Overview  Design Considerations  Development methods Architecture  Architecture Strategy's  System Architecture System Design Overview

System Overview Build a FSM that mimics the functionality of a standard vending machine (such as a coke machine) Web based interface that is portable and does not require a full web server (such as apache) to run Database used for storage of states of the vending machine

Design Considerations Need for multiplatform support to allow for cross platform development and testing Distributed version control Ability to demonstrat the web interface without access to the internet (self contained)

Dependencies  Python 2.x line (2.5+ required)  Django web framework  Web-browser with AJAX and Javascript support

Development Methods Bazaar / Launchpad for version control Python Enhancement Proposal 8  Used for coding style guidelines  Comment guidelines / ect

Architecture Strategies Python  Large standard library  Multi-platform support  Allows for focus on application logic instead of implementation issues. Django  MVC Structure  Simple database integration  Out of the box development web server

Architecture Strategies (cont) AJAX  Allows for communication with Django without page refreshes  Does not rely on external dependencies on the client machine (such as java or silverlight)  Smaller and more dynamic code base

System Architecture Functionality broken up into two pieces Front end  Consists of the user interface  Handles interaction with the user and displays balance / selection of products Back end  Handles the programming logic  Communicates with the front end via AJAX / XML Request's

System Design Overview XML DTD Database scheme Django Function / Web API URL's

XML DTD Communicates user actions and responses between django and the web interface Transaction XML DTD  Handles transaction request (purchase, balance change, balance inquery, ect) Response XML DTD  Handles the response to the transaction DTD request (after the business logic has been preformed)

Transaction DTD

Response XML DTD

Django Database Modes  Products  Users

Django (cont) Database Models (cont)  State

Example FSM Diagram

Django (cont) Views  GetIndex  ajax

AJAX Functions  AJAX : Sends and receives ajax request from django  Product_Selected : Generates an AJAX Request when a user selects a product  Insert_Money : Handles when a coin/bill is inserted  Dandle_Response : Handles the response from django (callback function)

References Python  Django  Style guide for python code PEP 8: 

Questions