Web - Based GIS: Front ends for enterprise

Integrating enterprise-wide systems into a consistent graphical user interface deployed over the Web provides significant advantages to electric utility and telecommunications companies. This paper first discusses technology used to deploy GIS Web systems. Next, specific implementation issues are addressed covering the design, development, and deployment of the graphical user interface and the component modules. The advantages and disadvantages of this system are then contrasted Finally, the paper presents examples of Web modules and their associated specifications.

GIS Web Technology
The most important concepts necessary for creating front ends for enterprise-wide management systems are ActiveX, Discrete Data Access Modules, and container 136 applications. At the first level of the GIS Web technology diagram, Figure 1, is the operating system. The operating system for this example is Windows NT. Distributed Component Object Model (DCOM) is a software development specification that defines how reusable components should communicate with each other regardless of whether they are on the same machine.

ActiveX is a protocol used for creating discrete, event-driven, and distributable components. Developers create ActiveX controls that can be combined in an HTML or Visual Basic container to create more complex applications. ActiveX controls have a graphic user interface and expose a portion of their data and methods. Exposing only some of their internals makes ActiveX controls reusable and modular. ActiveX controls can contain other ActiveX controls, a process called “encapsulation.”

Discrete Data Access Modules (DDAMs) are ActiveX modules with connections to databases, a graphical interface, and facilities for communication with other GIS DDAM modules. DDAM interaction specifications are developed by the customer to satisfy business processes and to integrate into container applications. DDAMs are the building blocks for creating applications that link data from enterprise-wide systems. DDAM can easily be created to access many commercial databases, GIS packages, or ODBCcompliant databases. DDAM can also access documents stored in any of the Microsoft suite of products. The most important interface consideration for Web GIS is that DDAMs can access enterprise-wide systems such as customer care, network management, billing, marketing, engineering, and inventory management. DDAMs can be constructed to access data stored in each of these systems’ database or by querying the system for the specified information. DDAM integrates with existing data; data does not need to be copied to a new format—it simply is accessed in place. This greatly simplifies the programming and allows companies in transition times to build working systems quickly.

Container applications contain one or more DDAM and handle the interaction and user interface. Container applications can be developed from existing ActiveX controls. Using existing ActiveX controls facilitates creating a DDAM system quickly. Containers are written in a combination of HTML, Visual Basic, and VB Script. The most important aspect of the container applications is that they provide a usable and consistent graphical user intetface. Properly constructed containers are capable of utilizing a plugand- play methodology. This methodology allows different DDAM to be combined in various manners to satisfy differing user requirements. Finally, container applications are distributed over the Web. Changes to DDAM or container application versions can be made at a central site and then distributed to any local or remote user automatically.

Figure 1. WebGIS Technology. The foundation layer is the Windows NT operating system. Distributed Component Object Model (DCOM) is the protocol that supports ActiveX. Discrete Data Access Modules (DDAMs) are created that access enterprise - wide systems. DDA Mare combined to form container applications. Each container application is usable with in the Web GIS application. The Web GIS application consists of a MS Access - type interface with multiple panels.