ABOUT PATTERNS IN GENERAL

In essence, patterns are structural and behavioral features that improve the "habitability" of somethinga user interface, a web site, an object-oriented program, or even a building. They make things easier to understand or more beautiful; they make tools more useful and usable.

As such, patterns can be a description of best practices within a given design domain. They capture common solutions to design tensions (usually called "forces" in pattern literature) and thus, by definition, are not novel. They aren't off-the-shelf components; each implementation of a pattern differs a little from every other. They aren't simple rules or heuristics either. And they won't walk you through an entire set of design decisionsif you're looking for a complete step-by-step description of how to design an interface, a pattern catalog isn't the place!

This book describes patterns literally as solutions to design problems because part of their value lies in the way they resolve tensions in various design contexts. For instance, an interface designer who needs to pack a lot of stuff into a too-small space can use a Card Stack. What remains for the designer is information architecturehow to split up the content into pieces, what to name them, etc.and what exactly the Card Stack will look like when it's done. Tabs? A lefthand-side list or tree? That's up to the designer's judgment.

Some very complete sets of patterns make up a "pattern language." These patterns resemble visual languages, in that they cover the entire vocabulary of elements used in a design (though pattern languages are more abstract and behavioral; visual languages talk about shapes, icons, colors, fonts, etc.). This set isn't nearly so complete, and it contains techniques that don't qualify as traditional patterns. But it's concise enough to be manageable and useful.