Data model

Throughout this chapter, the term job refers to a specific task or event that our mobile worker engages in. For example, a request to replace a hard drive in a computer at the bookstore is a job. A request to upgrade the firmware in the fuel-injection system at the refinery is likewise a job. The home office dispatches one or more jobs to the mobile worker on a regular basis. Certain data elements in the job are helpful to the mobile worker to accomplish his goal of completing the job. This information comes from the home office. Where the home office gets this information is not our concern in this application.

In this chapter's sample application, there are only two pieces of information the mobile worker is responsible for submitting to the dispatcher. The first requirement is that the mobile worker communicates to the home office that a job has been closed; that is, completed. The second requirement is the collection of an electronic signature from the customer, acknowledging that the job has, in fact, been completed. Figure 12.1 depicts these data flows.

Of course, there are additional pieces of information that may be helpful here, such as the customer's phone number, anticipated duration of the job, replacement parts required in the repair (including tracking numbers), any observations about the condition of related equipment, and much more. While these are very important to a real-world application, these pieces of information are extraneous to the goals of this chapter and are left as an exercise for you to extend the application for your own learning and use.

The next objective is to determine how data is stored and transported.

Home office / dispatcher

List of jobs sent to a specific mobile worker

Each job contains

Job id

Customer name


City, State, Zip

Product needing repair

URL to product information


Mobile worker


Job status (updated by mobile)

Signature (updated by mobile)

Mobile worker

Figure 12.1 Data flows between the home office and a mobile worker
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