ActiveX documents as GIS Web Client Applications
Craig McAdie
Smallworld Systems Ltd.
1140 West Pender Street, Suite 710
Vancouver, BC
Canada V6E 4G1
Abstract
The increasingly prominent role of Web-based client/server systems means that users expect these applications to
deliver more functionality. Typically, client applications are implemented as either an active server page or as a
stand-alone executable.
ActiveX documents combine the advantages of an application developed in Visual Basic with the ability to access
the features of the Internet Explorer web browser. This paper addresses and discusses the deployment of ActiveX
documents as web client applications.
The Client Application Tier of Web Based Applications
Three tier web-based systems have become a common mechanism for making GIS data accessible to end-users
across local Intranets and the Internet. When designed and deployed correctly, these systems provide the scalability
and versatility required to deliver this data to a large number of end users quickly and efficiently. As the name
implies, these systems are divided into three levels, or tiers:
- A data tier that contains the common datastores.
- A web, or business, tier that provides the business logic components and the communication mechanism that
performs the process of transferring data across the network.
- A client tier that consists of the applications that are deployed to the end users and which allows them to request,
view and process the data.
The data tier resides on the server; the web tier components can reside either on the server or on client workstations.
Client applications may be loaded from the server, but are generally executed on the workstations of the end users.
This paper focuses on the client tier and the options that are available for developing and deploying web client
applications.
The underlying architecture of three-tier web based systems, and more specifically the separation of the client
application tier from the business and data tiers, allows for a range of client applications to be designed and
implemented to meet specific end user requirements. Currently, the two types of client applications that are deployed
most commonly are that based on the standard web page and the stand-alone executable.
Because both types of client applications have distinct advantages and disadvantages, the decision to proceed with a
specific option will depend ultimately on the requirements of those who will ultimately use the application and the
corporate environment in which the application is to be deployed. If the functional and user interface requirements
are not complex, and the ability to deploy the application quickly and efficiently from the server is a priority, then an
extremely thin web page client may be preferable. If there are a number of different categories of end users which
have different requirements, then it may be desirable to deploy a stand-alone executable to those users who require a
richer feature set, along with a web page application to the other users.
