A tiny bit of language support can turn a simple text box into a compact and powerful way to let a user quickly supply complex data. An application can constrain the allowable text to adhere to a small and computer-friendly grammar that mirrors somewhat a natural human language. Even a highly constrained grammar can still produce a user experience that feels natural. This works best when the domain of text a user might enter is small, when the user can easily imagine what they can type, and when the designer and developer can collaborate on thoughtful construction of the grammar.
A simple example of a micro-grammar at work is a UI combining a scalar quantity and a unit into a single field, such as the measurement fields in Microsoft Word 2007. These fields throughout Word accept a variety of units, such as inches, metric centimeters, points, or lines. As in natural (here, English) language, the units directly follow the numeric value:
The fields on the left in the image above happen to be showing measurements in inches (") while those on the right are showing points, but all the fields accept all supported units. The controls not only parse out the value from the units, they can also convert and render measurements in a canonical format. In the default settings for the Microsoft Word on a U.S. system, indentations are converted to inches, and leading is converted to points.
Compare the above to an application like Adobe PhotoShop CS2 that uses standard operating system controls:
Here the user must enter units separately, requiring that they move the focus with the mouse or keyboard. The UI also looks significantly more cluttered. Word's text-parsing micro-grammar let one control in Word do the job of two in Photoshop. The trade-off is one of cleanliness versus discoverability. This efficiency is critical in cases like Word's Ribbon, in which a large number of controls are packed into a small space. On the other hand, using two controls makes clearer what units are supported. A UI with separate controls is also significantly easier to implement.
One distinct advantage of text boxes that support micro-grammars is that they can offer shortcuts to power users without compromising the simplicity of the typical user's experience. The date fields in Microsoft Outlook, for example, not only accept dates in local form, but also accept shortcut phrases such as "tomorrow" or "next Tuesday". Some supported shortcuts don't seem to add much value. The U.S. version of Outlook lets the user type the names of a number of common American holidays like "Christmas" (but not Easter, the date of which involves non-trivial astronomy, and even an overeager Microsoft Office developer has to stop somewhere).
It's dubious that the ability to type in "New Year's Day" as an appointment date has ever actually helped anyone—who schedules appointments on New Year's Day, anyway? Still, even these dubious shortcuts don't clutter anything up. Another advantage is that such text boxes allow the pasting of complete text from other sources directly into the UI in one step, letting the application do the work of breaking apart relevant information instead of forcing the user to do this by hand.
To have a program understand text the user has typed requires that a developer create a parser: a chunk of code that implements the rules of the grammar to determine what the user is trying to express with that text. If the desired grammar is extremely simple, a developer might hand-code a parser for it, but this can quickly get out of hand. More complex grammars typically entail the use of a parser generated by a tool. For example, if it's possible to restrict the supported input to a form known as a context-free grammar, there are a wide variety of tools for generating a parser that can handle such grammar.
Any attempt to optimize a micro-grammar for the nuances of one natural language will, of course, complicate matters if and when the need arises to localize the UI for other languages. Suppose some culture normally puts the units before the numeric value. Users in this culture might reasonably expect to be able to enter data that way. If the parser has been generated with a tool, it should be relatively straightforward for the developer to create a new grammar definition that swaps the position of those elements. The rest of the application logic should remain virtually unchanged.
I'm not sure how many software companies would actually go through the trouble to adapt a micro-grammar for a specific market. Then again, companies rarely go through much trouble to change the layout of a dialog like the one from PhotoShop above, in which the layout of the controls is heavily biased in support of the designer's natural language. The work required to update a well-factored grammar definition is likely less than that required to reposition a significant number of controls across a large number of pages or dialogs.