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ArcIMS Architecture

Specifically built to serve GIS on the Internet, ArcIMS is designed to make it easy to create map services, develop Web pages for communicating with map services, and administer sites.

diagram illustrating the ArcIMS architecture

ArcIMS operates in a distributed environment and consists of both clientside and serverside components. Typically, the client requests information from an Internet or Intranet server. Then the server processes the request and sends the information back to the client viewer.

Serverside Components

The ArcIMS serverside components include

  • ArcIMS Spatial Server
  • ArcIMS Application Server
  • ArcIMS Application Server Connectors
  • ArcIMS Manager

ArcIMS Spatial Server

The ArcIMS Spatial Server processes requests for maps and related information. When a request is received, the ArcIMS Spatial Server performs functions such as

  • Creating cartographic map image files
  • Streaming map features
  • Searching to query the database
  • Geocoding for address matching operations
  • Extracting or "clipping" data to create a subset that can be sent back in shapefile format

Two middleware processes, the ArcIMS Monitor and the ArcIMS Tasker, run in the background to support the ArcIMS Spatial Server. These can operate as either Windows NT services or daemon processes (on UNIX).

"The National Geographic Society has had as part of its mission for more than a century the distribution of geographic knowledge. It's a happy irony for me that now we can really do it, thanks to incredible tools like ArcIMS that make it possible to get maps almost instantly to millions of people around the world."        --Allen Carroll, Chief Cartographer, National Geographic Society

ArcIMS Application Server

The ArcIMS Application Server handles the load balancing of incoming requests diagram illustrating the ArcIMS application server's load handling capabilitiesand tracks what MapServices are running on which ArcIMS Spatial Servers. The ArcIMS Application Server passes a request to the appropriate ArcIMS Spatial Server. The ArcIMS Application Server is written as a Java application and runs as a Windows NT service or a daemon process (on UNIX).

ArcIMS Application Server Connectors

The ArcIMS Application Server Connectors are used to connect the Web server to the ArcIMS Application Server. ArcIMS provides three connectors:

  • Servlet Connector
  • ColdFusion Connector
  • ActiveX Connector

The Servlet Connector is the standard connector used for ArcIMS. It uses the ArcIMS language, ArcXML, to communicate from the Web server to the ArcIMS Application Server. ArcXML is the ArcIMS version of eXtensible Markup Language (XML). The Cold Fusion and ActiveX connectors work with custom clients and translate their own languages into ArcXML.

ArcXML

ArcIMS communicates between the different components using ArcXML. These ArcXML files look similar to HTML pages. The difference is that HTML describes the page structure for display while ArcXML provides the structure for describing the content.

ArcXML tags and attributes provide the structure for

  • MapService configuration files. These files describe how a map should be rendered including the list of layers that are used and how each layer should be symbolized.
  • Requests. Requests set a filter on an existing MapService configuration file that specifies which part of a map and associated data will be acted on.
  • Responses. Responses send the information back to the client.
  • ArcXML defines content for MapServices and is used for requests and responses between clients, middleware, and server.

Clientside Components

Requests are sent from three types of ArcIMS viewers:

  • HTML/DHTML viewers that send requests directly using ArcXML
  • HTML/DHTML viewers that use the ArcIMS ColdFusion or ActiveX Connectors
  • Java viewers including ArcExplorer–Java

ArcIMS includes clientside viewers:

  • ArcIMS Java viewer
  • ArcIMS HTML viewer

ArcIMS includes HTML and Java viewers as well as ArcExplorer 3 (Java edition). Users can customize templates to add logos, graphics, colors, and functions. The ArcIMS viewers determine the functionality and graphical look of the site. This is the map view that will be displayed in the end user's Web browser.

Next >> ArcIMS Manager

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