When browsing the web, you have to be connected. You don't think about this as you read this article. Typically, the cost to "surf" is a flat monthly fee billed to you or to your office. But when browsing via a mobile device, you may be accessing the web through a cellular network. This access typically results in a fee for the amount of time one is connected or the amount of data one accesses. This cost can factor into the success of a browser-based solution in mobile computing. Too much connectivity can run up those costs. In fact, Nokia researchers have concluded
that cost is "seriously restraining mobile browsing from becoming commonplace." Another cost is that normal web site interfaces may need to be altered to provide the most efficient time use. Today's web sites are rarely constructed for the most efficient use of time. In fact, some are built to encourage you to "linger" and stay on the site for long periods, presumably keeping you from the competitors.
WML vs. HTML vs. C-HTML vs.
Newer full-featured micro-browsers, such as Opera Mobile and Safari (used on the iPhone), can display HTML (or XHTML) complete with cascading style sheets and even client-side scripting. Therefore, the "normal" web site written largely with HTML/XHTML, CSS and client side scripts might be completely accessible in these browsers, even if they don't always offer the best interface given the constraints discussed earlier. However, in other cases, a web site or web application may need to be rewritten or otherwise dynamically converted into an alternative markup/wireless protocol. Again, there are plenty of choices. However there seems to be increased consolidation toward XHTML-Mobile Profile (MP). A lot depends on where (United States vs. Japan vs.
) and when (today, in a couple of years, etc.) you intend to offer your application and on what types of devices. Table 1 outlines some of the more popular markup options in use today.
Table 1. Micro-Browser Markup Languages and Protocols: While by no means exhaustive, here's a list of the most popular markup languages and wireless protocols used with mobile devices (excluding HTML).
||What is it
|XHTML-MP (WAP 2.0)
||Derived from and is a subset of XHTML
||+Developers can use the same tools for mobile and normal web sites.+More formatting power than WML.+WAP Gateway no longer critical component.- May display differently in different browsers.
|WML (WAP 1.x)
||XML document with features inherited from HTML. First generation wireless markup language.
||+WML and WMLScript are fairly easy to learn.+Was widely accepted.-WAP Gateway a concern in converting HTML to/from WML.-Soon to be phased out, but still used heavily in places like far east.
||A compact and simple form of HTML. Similar to WML.
||+ Offers features such as access keys and phone number shortcuts- Limited use; big in Japan—especially on DoCoMo phones.
Certainly, to reduce having to maintain dual sites and in order to offer the same rich display/features, the trend is to have micro-browsers behave more like "normal" browsers. Some analysts, like Craig Mathias
, have suggested the time to retire micro-browsers altogether is drawing near. At present, however, this is not always possible—or wise—given mobile devices' constraints and differences.
Give Me a Browser
Speaking of that micro-browser, just how did it get on the mobile device? You may assume that the devices all ship with a browser. That is usually true. However, you might also assume that the browser used on the device is the same one that it shipped with. This is increasingly not the case! As devices become more open to allow owners to add their own software and common runtime engines (such as the Java ME virtual machine), a demand has arisen for alternative browsers with alternative features. Opera Mini
claims to be the world's most popular micro-browser with over 15 million users.
Whether it is your device's default browser or not, the Opera web site just asks you to point your cell phone browser to operamini.com to download and install the latest copy. It's as simple as that. In fact, there are probably more micro-browsers than there ever were "normal" browsers. Table 2 shows a list of some of the user-installable browsers.
Table 2. User-Installable Micro-Browsers: While by no means complete, here is a list of some of the more popular/well known micro-browsers that can be installed on mobile devices; most often cell phones.
These alternative browsers add complexity to thin-client solutions. Mobile developers take note: standards and standards adherence will be pivotal to making the thin client approach work. Just ask a web developer about the impact of all the alternative choices in browsers, added/removed plug-ins, and control of features such as script execution and cookies on a "normal" web site. As with most web sites/applications, lines must be drawn about what will ultimately be supported.