4. paradigms


Choose one paradigm of interaction and find three specific examples of it, not included in this chapter. Compare these three - can you identify any general principles of interaction that are embodied in each of your examples (see Chapter 7 for example principles)?

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There are clearly a variety of ways a student may answer this question, depending on which paradigm is chosen as a focus. It may be difficult for students to think about how older paradigms presented in the textbook might have modern examples. For example, what would be a modern example of a time-sharing system? Expect that students will feel more comfortable with the later examples of paradigms for this exercise. Also, when this part of the book was originally written, the paradigms/historical section was immediately followed by a discussion of principles of interaction. Therefore, it is reasonable to have students consider this question after having read and understood Chapter 7 of the 3rd edition.

Here is an example answer. We will consider the use of metaphor. Metaphors are introduced to support the general learnability principle. Here are some examples of the use of metaphor:

1) The electronic spreadsheet. This is a fairly old, but classic example of the use of metaphor that resulted in a major "killer app" for personal computers. Before electronic spreadsheets, it was traditional to keep various accounting tasks on large ledger sheets, which facilitated row and column tabulation. Columns of numbers could be easily lined up for mathematical operations performed by hand. The row and column metaphor of the ledger sheet (or physical spreadsheet) was replicated in the original electronic spreadsheet programs introduced in the early 1980s (Lotus 1-2-3 and Microsoft's Multiplan). One specific principle of learnability that the spreadsheet supports is synthesizability. Spreadsheets are very good at supporting "what if" calculations. A complicated series of calculations (like determining monthly expected expenses for a family) oftentimes depends on various parameters (e.g., how many times will the family dine out or how many times will the car need refueling). The calculation can be easily parameterized with a number of arguments and the value of the argument can be changed, resulting in a new answer to the overall question. Whenever the user changes the value of some parameter, by changing the value in a "cell" of the spreadsheet, all dependent calculations are performed and the overall spreadsheet is updated. This makes it easy for an individual to synthesize the effect of the change he just made. Spreadsheets became very popular as simplified programming environments, initially for numerical calculations in financial applications. Over time, just as with the word processor, the metaphor to the original paper spreadsheet has been broken, and the kinds of things we do with an electronic spreadsheet (like perform complicated searches of a database of records) do not even have a clear relationship with the physical world.

2) Web shopping cart. Online shopping is a big application for the world wide web. Initial interfaces often made it difficult for individuals to understand how to purchase multiple items. By introducing the notion of a shopping cart, designers could leverage a familiar "brick and mortar" metaphor for shopping: place items in a cart and then proceed to checkout when shopping complete. This user of a metaphor leverages off familiarity to enhance learnability.

3) Electronic diaries or electronic calendars. One of the most popular PDA applications is for diary or calendar management. Paper-based calendars serve as a good metaphor for most electronic interfaces and again leverage familiarity.

4) Electronic whiteboards, like the LiveBoard or SmartBoard. These typically have an upright display that can be written upon with a stylus. The SmartBoard is a particularly good example of applying the metaphor of a traditional whiteboard, having separate "markers" for writing in different colors, even though this is not strictly needed in the electronic domain. Some even provide a special utensil for erasing. Some electronic whiteboards actually leverage the surface of a regular whiteboard and allow the use of regular markers (with special holders) to make the user feel even more comfortable with a familiar writing experience.

Other exercises in this chapter

ex.4.1 (open), ex.4.2 (tut), ex.4.3 (tut), ex.4.4 (tut), ex.4.5 (open), ex.4.6 (tut), ex.4.7 (tut)

all exercises for this chapter