Early Design n How to Start Intelligent Borrowing

Use of Existing Applications n Build add-ons – look at systems users already know n Copy interaction techniques – copy the style of menu selection, organization of screen elements, etc. (where appropriate) n Understand why design was done in the way it was done with the existing interface Copyright 1999 all rights reserved

Reasons for Design Decisions n Human motor performance arguments – items that are co-selected should be close – small items are hard to select – selection while holding the mouse button down is a harder motor task Copyright 1999 all rights reserved

Reasons for Design Decisions n Human memory arguments – keyboard entry requires someone to remember the name of the item – screen selection only requires someone to recognize the item – long command sequences hard to learn and to hold in the user’s head Copyright 1999 all rights reserved

Reasons for Design Decisions n Problem-solving arguments – problems can be hard to solve if represented poorly – if the user has to map their problem representation into a different one on the screen, the problem will be harder to do Copyright 1999 all rights reserved

Reasons for Design Decisions n Human visual performance arguments – important items stand out by varying properties of items, e. g. , color, shape – user search guided by organization of screen elements, e. g. , user’s eye navigates from left to right and top to bottom Copyright 1999 all rights reserved

Reasons for Design Decisions n Design convention arguments – user is already familiar with process order or arrangement from other interfaces – most of user interface design requires designers to work within the tight constraints of existing designs Copyright 1999 all rights reserved

Reasons for Design Decisions n Diversity Arguments – Application may be used in different countries • large American trashcan on Macintosh computer looks silly in Europe • difficult to map single menu command to one in another language - requires re-organizing the menus – Application may be used by casual and dedicated users • menu selection and accelerator keys both used Copyright 1999 all rights reserved

When you must invent n What if the system’s never been built before? (e. g. , one-of-a-kind) – Look harder for existing ideas • e. g. , coffee machine design copied to bank machine – Try to uncover a conceptual model the user already has – Use an iterative process • Build a little, test a lot Copyright 1999 all rights reserved