1. Gary MarsdenSlide 1University of Cape Town Building systems We will now look at the techniques and tools used to create interactive systems This will require us to look at –design process –abstract representation –design software

2. Gary MarsdenSlide 2University of Cape Town Design process There are basically three parties involved in creating a product –The designer –The creator (or programmer) –The user There is no direct communication between creator and user, it is mediated through the designer

3. Gary MarsdenSlide 3University of Cape Town Sapir-Whorf hypothesis This refers to the problems of communicating ideas when the vocabulary does not permit ideas to be expressed Designers, users and programmers have this problem The use of prototypes, or mock-ups results in premature commitment

4. Gary MarsdenSlide 4University of Cape Town Prototypes Creating a paper mock-up (or story board) is a great way to communicate between designers and users. The programmer must translate this into code –not always possible Using an interface design program overcomes this difficulty, but produces spaghetti code –Macromedia Director often used in this role

5. Gary MarsdenSlide 5University of Cape Town State charts State charts were proposed by David Harel as a way of abstractly specifying an interface’s behaviour It is possible to translate state charts directly into code, so hopefully the prototype can be based on a more structured approach

6. Gary MarsdenSlide 6University of Cape Town In the beginning was......Finite state machines! Very nifty way of analysing interface complexity –based on graph theory, well understood Alas, state diagrams grow exponentially as new features are modelled, making them impractical for real applications

7. Gary MarsdenSlide 7University of Cape Town Case Study To learn about state charts we will look at a case study analysing a CD player –We first use finite state automata to model the interaction –We will then use State charts to show how them improve over FSM’s