Getting Started
When developing smart client mobile applications, several items outside of the development environment have to be addressed – creating a remote database, creating synchronization logic, and starting a synchronization server. These are not specific to the mobile development tool, but are related to the mobile database and synchronization technology used. In this case, the Adaptive Server Anywhere (ASA) database and MobiLink synchronization technology from SQL Anywhere Studio are used, as they're included in the Pocket PowerBuilder package. These technologies offer integration with other enterprise databases on the server-side including Sybase Adaptive Server Anywhere, Sybase Adaptive Server Enterprise, Oracle8i and 9i, Microsoft SQL Server, and IBM DB2. Figure 1 depicts a smart client architecture.

Before a mobile application is developed, the following three steps need to be performed:
1.   Create a Remote Database
Defining the remote database is one of the most important steps in creating a mobile application. It defines what data is available to the remote user, consequentially dictating the functionality of the remote application. In general, the remote database is much smaller than the consolidated database (for obvious reasons!). It will typically have a subset of the schema from the consolidated database, although this is not an absolute requirement. The most important thing is that the data types of the remote data being synchronized match the corresponding consolidated database data types.

The Database Painter in Pocket PowerBuilder can be used to create the remote ASA database. This will work well for developers who are intimately familiar with their consolidated database schema. If this isn't the case, a data-modeling tool may be a better choice. The database administration tool that comes with SQL Anywhere Studio includes a migration utility that can be used to create a remote ASA database with the same schema as an existing enterprise database.

2.  Creating Synchronization Logic
The synchronization logic controls the subset of data that flows between the remote and consolidated databases. It defines what data is synchronized and how the changes are applied at each end. It's a critical component of smart client applications (see sidebar). When using MobiLink Synchronization, a variety of technologies including SQL, Java, and any .NET programming language can be used to define the synchronization logic.

3.  Starting the Synchronization Server
Communication between the mobile application and the enterprise goes through a synchronization server. This server can either reside on the same machine as the enterprise database or on a machine of its own.

Pocket PowerBuilder can be used to start the MobiLink Server from within the IDE. There are also options available to have a default set of synchronization scripts created for you, providing a great starting point for developing custom synchronization applications.

Building a Smart Client Pocket PowerBuilder Application
When developing occasionally connected mobile applications in Pocket PowerBuilder, five key steps have to be performed. Each of these steps will be addressed at a high level. If you're looking for an in-depth tutorial on Pocket PowerBuilder, you can purchase or download an evaluation copy from Sybase at www.sybase.com/pocketpowerbuilder, and go through the SalesDB tutorial that's included with the product.

Step 1:  Create the Database Profile
The Pocket PowerBuilder application is developed using the remote database, not the consolidated. This is logical, since the deployed application will be running on a Pocket PC device and won't have direct access to the consolidated database.

Before developing the application, a Database Profile for the remote database has to be created. In Pocket PowerBuilder select the Tools —> Database Profile… menu option to create the profile for the remote database. This database profile will be used throughout the entire application development process.

Step 2:  Design the Application's Forms
The Pocket PowerBuilder development environment contains four main areas:
1.  The PowerBar located at the top of the IDE is where all of the most common actions can be invoked.
2.  The Workspace View on the left side of the IDE is where projects are managed and is the main navigation area for a Pocket PowerBuilder application.
3.  The Application Painter is where Windows are designed using drag-anddrop development. There are a variety of views for an application including a WYSIWYG Layout View, a Code View, an Event List, and a Function List.
4.  The debug/output console is where the developer will find build information as well as warnings or errors that may occur.

The first item that needs to be created when starting a new application is an application workspace. Within the workspace, targets are then added; multiple targets can exist within a single workspace. Inside of the target is where the developer can then add new Pocket PowerBuilder Objects (Windows, menus, non-visual objects, etc.), DataWindows, database and synchronization components, and projects.

When designing a smart client mobile application, developers typically start by designing the application's layout. This involves creating a number of forms (Windows) and adding visual components to them. Most Pocket PC applications consist of multiple screens that are navigated by menus and tab controls (MDI applications are not supported on Windows CE). Since the screen size of Pocket PC devices is significantly smaller than that of desktops, the user interface and navigation of the handheld application require special attention. Pocket PowerBuilder has some features that are specifically designed to make Pocket PC development straightforward. These features include a menu painter, tab controls, Soft Input Panel (SIP) integration, default window sizes to match those on a Pocket PC device, and specialized window controls such as Smart Minimize (X) and Close (OK). All of these properties are accessed using property sheets as shown in Figure 2.

In addition, Pocket PowerBuilder comes with a rich set of prebuilt components to facilitate the development of sophisticated mobile applications. A partial list of these controls includes Command Button, Picture Button, CheckBox, Radio Button, Static Text, List View, Tree View, List Box, DropDown List Box, Edit Mask, Single Line Edit, MultiLine Edit, Progress Bar, and Scroll Bars. These components are used frequently during mobile application development. For sophisticated database integration and presentation logic, the DataWindow component is a powerful option.

Step 3:  Create DataWindow Components
When it comes to creating data-driven applications, the DataWindow is Pocket PowerBuilder's crown jewel. The DataWindow provides the ability to incorporate database access (SQL inserts, deletes, updates, etc.) and advanced presentation logic (Freeform, Graphs, Grids, Groups, and Tabular) into a single component. The ease-of-use and robustness of this component considerably increases the productivity of mobile application developers. Figure 3 shows a DataWindow component using a graph presentation style.

Once the user interface is created, PowerScript is used to add business logic to the application, ideally by using nonvisual objects. The separation of presentation logic from business logic has been identified as the preferable development strategy for some time now, and it definitely makes sense for Pocket PowerBuilder applications.

At this point, the application can interact with the remote ASA database, but it doesn't have any form of enterprise integration. This is where enterprise data synchronization comes into play.

Step 4:  Add Synchronization Support to the Mobile Application
This is the final and traditionally one of the more difficult stages of application development. Logic has to be added to the client application to communicate with the MobiLink Client as well as to provide the application user with the ability to change any synchronization options that may need to be altered at runtime. Fortunately for Pocket PowerBuilder developers, this has all been automated with the MobiLink Synchronization wizard as shown in Figure 4.

The wizard goes through every detail required to add synchronization to a Pocket PowerBuilder client application. During the wizard, the developer will be required to specify:

The output of the wizard depends largely on the options that were selected on the wizard pages. Minimally the wizard will create an NVO that controls the MobiLink Synchronization client and a generated function to instantiate the NVO and launch a synchronization request. Beyond these two items, it's also possible to automatically create a MobiLink status window to display the synchronization status, as well as a window to allow the application user to change the MobiLink command-line parameters at runtime. Both of these generated windows can be used as is, or can be customized by the application developer.

At this point all the developer has to do is add the appropriate code to start the synchronization request. This is usually added in the click event of a menu item, but can be located anywhere within an application. The code to launch the synchronization will look like this:

// Start synchronization
if gf_sync_salesapi("ml_username", "ml_password")
<> 0 then
MessageBox("Error", " MobiLink
Synchronization Error. ");
End if
// Fetch data
f_refresh_orders(-1)

Step 5:  Deploy the Application
Once the synchronization component of the application has been implemented, it's time to test/deploy the application. Pocket PowerBuilder provides integrated deployment to the following environments:

For smart client applications, two additional items need to be deployed along with the mobile application:

Finally, for organizations that have larger numbers of remote users or users in many geographies, mobile software deployment and management software is worth looking into. Manage Anywhere Studio from iAnywhere Solutions provides a way to centrally manage all of the mobile assets within an organization.

Conclusion
Smart client mobile applications with database and synchronization provide a way for organizations to guarantee anytime, anywhere data access to their mobile workers. Pocket PowerBuilder has all the components required to develop sophisticated smart client applications. With the tight database integration and MobiLink Synchronization wizard, Pocket PowerBuilder will drive the development of smart client mobile applications for years to come.

SYNCHRONIZATION IS THE KEY
With the shift from online only to smart client application models in mobile computing, a new emphasis has been placed on mobile database and synchronization technologies. While most developers clearly understand the issues surrounding a mobile database, there are often many questions around what should be included in an enterprise synchronization product. Here are a few key items to take into consideration:

When evaluating mobile application technologies, pay particular attention to the synchronization component of the solution. A complete solution will address the main issues listed above in a flexible, open manner. In smart client applications, this technology will integrate your mobile data with your enterprise systems.