A pattern approach to interaction design ebook

With Object-based Undo, each object has its own action history. Upon selecting the object, the users can undo actions done on the object. Naturally, this requires the application to have a clear concept of an 'object' and is therefore not applicable for bitmap editors. See Zhou and Imamiya for more on Object-based Undo. If the application is a multi-user application and uses undo, the application must distinguish between local actions and global actions.

That leads to multiple histories and requires special semantics for what happens when undoing actions. See Abowd and Dix and Sun and Ressel and Gunzenhouser for more on multi-user undo issues. Offering the possibility to always undo actions gives users a comforting feeling. It helps the users feel that they are in control of the interaction rather than the other way around. They can explore, make mistakes and easily go some steps back, which facilitates learning the application's functionality.

It also often eliminates the need for annoying warning messages since most actions will not be permanent. As in all MS Office applications, in Word the users can see the history of their actions and undo one or more of them. The actions are briefly described and the users can select a range of actions to be undone. After selecting undo, users can even redo the actions. In Photoshop a selective undo is also possible.

By moving the slider, users can do the normal multi-level undo but they can also drag an action into the trashcan and thereby do a selective undo. Operations that depended on that action are automatically deleted as well of they are not relevant anymore. Most implementations of multi-level undo are based on the Command Gamma et al pattern. When using the Command pattern, most functionality is encapsulated in Command objects rather than in other controlling classes.

The idea is to have a base class that defines a method to "do" a command, and another method to "undo" a command.

Then, for each command, you derive from the command base class and fill in the code for the do and undo methods. The "do" method is expected to store any information needed to "undo" the command. For example, the command to delete an item would remember the content of the item being deleted. Log in Join our community Join us. Open menu Close menu. Join us. An ID pattern usually consists of the following elements: Problem : Problems are related to the usage of the system and are relevant to the user or any other stakeholder that is interested in usability.

Use when : a situation in terms of the tasks, the users and the context of use giving rise to a usability problem. This section extends the plain problem-solutions dichotomy by describing situations in which the problems occur.

Principle : a pattern is usually based on one or more ergonomic principles such as user guidance, or consistency, or error management. Solution : a proven solution to the problem. A solution describes only the core of the problem, and the designer has the freedom to implement it in many ways. Other patterns may be needed to solve sub problems. However, formatting rules can vary widely between applications and fields of interest or study.

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Write a review Rate this item: 1 2 3 4 5. Preview this item Preview this item. Series: Wiley series in software design patterns. Subjects Human-computer interaction. Janko, S. Ars Electronica Center: Museum of the Future.

Ars Electronica Center, Linz, Austria. Kim, S. Interdisciplinary Cooperation. In Laurel B. Miller, G. Nielsen, J. Usability Engineering. Morgan Kaufmann, San Francisco. Norman, D. The Psychology of Everyday Things. Basic Books, New York. Erlbaum, Hillsdale, NJ. Sutcliffe, A. Patterns, Claims and Multimedia. IOS Press, Amsterdam, Tidwell, J. Interaction Design Patterns. Tognazzini, B. TOG on Interface. Jan O. Borchers 1 1. Personalised recommendations.