The reason for the
<card> tag is that WML
structures its content differently from HTML. Instead of a file being
a long stream of content, a file of WML represents a deck
Only one card is displayed at a time, but you can link from one card
to another and store several in a deck in the same file. Each
individual card does in fact behave very much like an HTML page, so
you can think of a WML deck as being similar to a number of HTML
pages all grouped together. It’s good WML style to use decks of
cards to group together related information or user interactions.
Cards in a deck are all downloaded at the same time, so the user has
to wait only once, and the others can be accessed almost instantly.
Conversely, it’s bad WML style to overuse cards, cramming too many into a single deck (and hence into a single downloaded file). Even if you think 30 cards of information are all relevant at the same time, the user will get bored waiting for all of them to download before she gets to see the first one. It is hard to put a fixed limit on the number of cards you should use, but here’s a general rule of thumb: if you find yourself using more than five or six cards in a single deck, you should think hard about how your pages are organized. Although you shouldn’t concern yourself too much with the transmission of the content, another thing to bear in mind is that many devices can’t cope with large files. (The Nokia 7110 cell phone, the most popular WAP device in Europe, has trouble if the deck is more than about 1400 bytes after being passed through the gateway.)