Tracking Users Using WML
This article describes how to provide Web content to mobile devices through WML (Wireless Markup Language). More specifically, this article covers how to track users; that is, how to recognize a repeat visitor to your site.
WML and WMLScript version 1.1 are supported by the majority of mobile devices in use today. The articles assume a working knowledge of HTML and general Web technologies, and further assume that you have read the previous article(s) in this series.
The Value of Recognizing Users
There are a variety of reasons to implement a recognition system that acknowledges that a user that has previously visited your site. The most useful of these reasons is to remember user preferences.
For example, suppose that you offer a service of finding particular restaurants near a user. Each user may prefer a certain type of food, environment, etc., and knowing where the user is located is important so that you can find restaurants in that vicinity. Of course, users don't want to input all their preferences every time they visit your site—it's better to save most of the settings, recognize users when they return, and recall their settings.
How To Recognize Users
When WML was first implemented, the code could retrieve the user's cell phone number from the device; this phone number could act as a unique identifier. Unfortunately, this ability was recognized as an invasion of privacy, and the feature was discontinued. Now there is no way to retrieve a unique identifier from the user's device.
What options are left? You could have the user input his or her telephone number on each visit, assign the visitor a login name, or have the user enter an identifier during each visit. Better yet, why not store the identifier on the user's device for recall each time he or she visits your site?
Cookies: The Good, the Bad, and the Ugly
The term cookie refers to the HTTP technology that allows a site to store data on a user's machine. When cookies were first used, they were fairly innocuous, intended primarily for storing user preferences. However, it didn't take long for the business side of the Web to realize the potential of cookies and begin using them for their own purposes—tracking user activities, shopping habits, and other bits of personal information.