Notification content types

A WML service can send notifications containing one or more of the following entities:

• Alert--a command that instructs the UP.Phone to beep or display a visual signal to notify the subscriber that new information is available.
• Cache operation--a command that removes an individual URL, or all the URLs for a service, from the UP.Phone cache.
• Decks
• Images
• Digests

The deck, image, and digest content types are described on page 54. The sections below describe the alert and cache operation content types in more detail.

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Alerts

From the user's perspective, the most obvious notification content type is an alert. An alert typically includes a short message (or title) and a URL that the user can request.

When a WML service sends an alert, the UP.Phone can do any of the following depending on the urgency specified:

• Beep, buzz, or flash a light, indicating that the alert has arrived (these features are not available on all UP.Phone models).
• Display a popup message card (shown in Figure 5-1) which informs users that an alert has arrived and allows them to view it or skip it.
• Display an alert icon (as shown in Figure 5-1)

The user can configure the UP.Phone to enable or disable each of these indicators.

Figure  5-1.     Popup message from the UP.Mail service

In addition to providing the alert indications described above, the UP.Phone adds each alert it receives to its Inbox card. The Inbox card is normally accessible from the user's Home Menu (as shown in Figure 5-2).

Users can navigate to the Inbox card at any time to view the alerts they have received most recently. When the user chooses the alert in the Inbox, the UP.Phone requests the URL provided by the alert.

Figure  5-2.     Inbox card displaying UP.Mail and UP.Market alerts

NOTE     Most devices running the 4.0 UP.Browser reserve approximately 1500 bytes for storing nine alert titles and associated URLs in the Inbox. As a result, you should limit your alert information (title and URL) to a combined size of 160 bytes. You should also keep your alert title as short as possible so users can read it without scrolling.

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Cache operations

UP.Phone caching can greatly improve the performance perceived by the user. When a user visits a URL, the UP.Phone caches it. The next time the user requests the URL, the UP.Phone retrieves it directly from cache instead of re-requesting it from the UP.Link Server (see page 51 for more information).

You can control when a URL expires from the cache by including a <meta> element in the deck header that specifies the time to live (TTL). In some cases, however, you may want to explicitly remove a URL from the cache--for example, if it becomes obsolete before its TTL expires. To remove a URL from the cache, you must send a cache operation to the device. Cache operations can instruct the UP.Phone to remove individual URLs or all URLs for your service from the cache.

As described on page 59, you can include a cache operation in a digest along with WML content. To remove a URL asynchronously "behind the scenes" (in other words, without waiting for the user to request the digest), send a notification that contains a cache operation.