17. models of the system


To some extent undo is similar to the 'back' command or button found in many web browsers, help systems and hypertext systems. Is the 'back' button on a browser just like undo? Hint: consider scenarios where the pages are web forms updating a database

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This is similar to the comparison made in chapter 16 of Human-Computer Interaction (section 16.6.2) between undo and reversability. The 'back' button takes you to the previous web page, but does not undo any database updates, etc., performed by the web form.

Other exercises in this chapter

ex.17.1 (ans), ex.17.2 (ans), ex.17.3 (ans), ex.17.4 (ans), ex.17.5 (tut), ex.17.6 (tut), ex.17.7 (tut), ex.17.8 (tut), ex.17.9 (tut), ex.17.10 (tut)

all exercises for this chapter