Drawing the line

InTech, Jul 2004 by Williamson, Rob, Weber, John

SVG represents an ideal technology for the creation, delivery, and management of smart graphics. The case studies demonstrate the difference between static SVG and data-driven dynamic SVG. With dynamic SVCi, the code base becomes significantly smaller and at the same time delivers more information. It also eliminates costly and time consuming design involvement when multiple outputs change based on one set of data.

Creating visuals

Creating a rich visual interface for one or more Web services is still a laborious task. The developer must request user interface (UI) mock-ups from a designer and then inspect the Web Service Definition Language (WSDL) carefully to determine how the information can map from the service to the UI.

In one case a simple UI element like a drop-clown list needs populating. If the application needs to display current weather conditions, then how does "overcast" turn into an image of a cloud for the user? What device displays the cloud? Will a raster image work? Does the client have the processing power to interpret the data?

All of these questions take time to answer and thus cost the user money and effort. Such issues also increase the effort or may even prevent the solution from being reusable in another application.

Workflow issues

Often the design process either reaches beyond the capabilities of the underlying system or fails to recognize some required functionality that the system can provide. This is sometimes a limitation of the information collection phase of a development project; more often it is a result of a simple change in the business goals during development.

The developer returns to the designer (and vice versa) to explain that certain applications are or are not available and offers alternatives based on coding principles.

Compare this to the world of current desktops. Here, the answers are easy. Many good UI frameworks are available that include list boxes, check boxes, and any other UI controls imaginable. Many tools exist that allow you to lay out and customize your interface, with clear ties to the APIs set out by your DLLs or other coding modules.

Outside of the standard GUI controls, visual interface development needs are not in the Web service application development paradigm. In this environment, developers must create everything from scratch.

ASP, .NET, and JSP provide the language to do so, but the tools, the libraries, and the precedent aren't available. Many standards forums are attempting to address this problem, but the tools are still missing and the focus is still on traditional UI controls. A number of IDEs have emerged to solve this problem by providing attributes-based tools that build dynamic interfaces combining more than simple UI.

Take, for example, the creation of a simple dialog in a Web-based application that consumes Web services. The type of controls you use in your dialog should be completely dependent on the Web service interface. If the Web service is looking for Boolean parameters and returns a list of strings, then a check box may be the proper control to call the function-and a list box populates with the results. Because Web services provide an XME standard for their definition, you can clearly visualize the structures for these interfaces.