The technology of interactive Web mapping facilities only provides half part of truly Distributed GIS. The client-side applications like Java applets and ActiveX controls, and dynamic HTML are designed mainly for graphic display of maps rather than truly providing GIS operations and analysis. A comprehensive Distributed GIS framework should provide both on-line mapping functions and real-time geospatial analysis and GIS operations. The chapter will introduce the LEGO-like dynamic GIS service components and their functions for distributed GIS. Three architecture models of Distributed GIS: a generic distributed GIS architecture model, Distributed GIS for a single site, and Interoperable Distributed GIS will be discussed in detail. The chapter will also describe two approaches of implementation: the CORBA/Java model, the COM+/ActiveX model.

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Chapter 5 Framework of Distributed Geographic Information Services

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• The Open GIS Consortium Implementation Specification (http://www.opengis.org/techo/implementation.htm)
  OGC is an international industry consortium of more than 220 companies, government agencies and universities. The core mission of OGC is to deliver spatial interface specifications that are openly available for global use. Open interfaces and protocols defined by OpenGIS® Specifications support interoperable solutions that "geo-enable" the Web, wireless and location-based services. This webpage links to Open GIS Implementation Specification, which are the software engineering specifications. Any software developer can use this information to build a product that is capable to communicate with any other software that implements the same specification(s). For example, OpenGIS® Web Map Server Interfaces Implementation Specification specifies the behavior of a service that produces georeferenced maps and operations to retrieve a description of the maps offered by a service instance, to retrieve a map, and to query a server about features displayed on a map.
  

• ISO/TC 211 (http://www.isotc211.org)
  The Technical Committee of International Organization for Standardization (ISO/TC) 211 is responsible for the standardization in the field of digital geographic information. This work aims to establish a structured set of standards for information concerning objects or phenomena that are directly or indirectly associated with a location relative to the Earth. These standards may specify, for geographic information, methods, tools and services for data management (including definition and description), acquiring, processing, analyzing, accessing, presenting and transferring such data in digital/electronic form between different users, systems and locations. This websites provides detailed information on the related projects, documentation, suggested models, etc. Updated presentations and publications are also available online.
  

• CORBA (http://www.corba.org)
  CORBA stands for Common Object Request Broker Architecture. It is Object Manage Group (OMG)'s open, vendor-independent architecture and infrastructure that computer applications use to work together over networks. Using the standard protocol IIOP, a CORBA-based program from any vendor, on almost any computer, operating system, programming language, and network, can interoperate with a CORBA-based program from the same or another vendor, on almost any other computer, operating system, programming language, and network. If you are totally new to CORBA, don’t worry. You can take the tutorial to get yourself familiar with the program. If you are familiar with CORBA, you can explore the specifications or find the training programs offers by a list of companies.
  

• Java (http://java.sun.com)
  This is an complete and comprehensive introduction on Java technologies, which includes Sun company’s main products Java 2 platform and XML. You can go through the tutorial to get hands-on experiences on how to use these technologies, explore the detail information on those products, and easily download the platform, code examples, etc.
  

• COM+ (http://www.microsoft.com/com/tech/COMPlus.asp)
  COM+ is one of Microsoft’s products that extends to the Component Object Model (COM). COM+ builds on COM's integrated services and features, making it easier for developers to create and use software components in any language, using any tool. Delivered on the Microsoft® Windows® platform, COM+ is designed to preserve and extend developers' current investments in COM. This wet site provides a wealth of resources of COM+. You can explore the COM+ resource CD online to find out the technical aspects of COM+, its applications, related white papers and presentations, etc. You can also check the Microsoft internal and external web links to find out technical information, resources, training and courses on COM and COM-based technologies.

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