The tremendous development of computer technologies and telecommunication networks allows for the emerging of Distributed GIS. The originally centralized mainframe GISystems has been evolved along with the technology development to personal desktop GIS, and to currently Distributed GIServices which include the applications of wired Internet GIS and wireless mobile GIS. This chapter will cover the underlying technologies that support the evolution of the distributed GIServices. The early development history of distributed GIS will be first introduced followed by the introduction on the two current industry standards of Internet GIS. Basic concepts of 2-tier client/server model of the Web, including HTML, HTTP, and Web browsers will be discussed in order to introduce the static Web mapping technology, including HTML forms, CGI, Servlets and Active Server Pages (ASPs). Then the architecture of Interactive Web GIS that covers Dynamic HTML and client-side applications such as Plug-ins, ActiveX controls and Java Applets will be discussed in detail.

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Chapter 4 Technology Evolutions of Web Mapping

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• The Xerox Map Viewer (http://mapweb.parc.xerox.com/map/)
  "The Xerox Map Viewer has been deactivated"
  

• GrassLinks (http://regis.berkeley.edu/glinks/)
  GRASSLinks is a World Wide Web interface to a geographic information system (GIS), offering public access to mapped information. GRASSLinks provides GIS display and analysis tools to facilitate data sharing and cooperation between environmental planning agencies, public action groups, citizens, and private entities. In the website, you could select different data layer from its geodatabase to review the GIS layer and perform geospatial analysis.
  
  
• Alexandria Digital Library (http://www.alexandria.ucsb.edu/)
  The Alexandria Digital Library project is headquatered on the campus of University of California, Santa Barbara. This wetsite provides detailed information concerning the project itself, the related projects, services, documentation, etc. Most importantly, the digital library interface is also provided for the users to access multiple digital spatial information. You could use different methods, such as geographic region search, time period search, word search, to querry the geospatial datasets for maps. Maps can be viewed through the map viewer.
  
  
• Digital Library Initiative Phase I (http://www.dli2.nsf.gov/dlione/)
  The Digital Library Initiative's focus is to dramatically advance the means to collect, store, and organize information in digital forms, and make it available for searching, retrieval, and processing via communication networks -- all in user-friendly ways. Research into digital libraries is research into network information systems, concentrating on how to develop the necessary infrastructure to effectively mass-manipulate the information on the Net. The key technological issues are how to search and display desired selections from and across large collections. Phase I started in 1994, and was finished in 1998. This website provides links to six digital library projects carried out by different university, as well as the links to d-lib magazine. A list of useful digital library information and resources is also collected and presented by the website.
  
  
• Digital Library Initiative Phase II (http://www.dli2.nsf.gov/)
  The website provides comprehensive links to the undergoing domestic and international projects under Phase II. The user can also check the news and events, newsletters and magazines on digital library research. Useful glossary is also provided.
  
  
• The Open GIS Consortium (http://www.opengis.org/)
  Open GIS Consortium (OGC) is an international industry consortium of more than 220 companies, government agencies and universities to develop publicly available geoprocessing specifications. Open interfaces and protocols defined by OpenGIS® Specifications support interoperable solutions that "geo-enable" the Web, wireless and location-based services, and mainstream IT. You can view and download OpenGIS specifications, check for the interoperability program which includes a series of hands-on engineering initiatives to accelerate the development and acceptance of OpenGIS Specifications. The website also provides comprehensive links to Open GIS resources. It is a good site to check for the updates and progresses made regarding Open GIS.
  
  
• 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.
  
  
• ESRI ArcIMS Java Viewer Demonstration (http://www.esri.com/software/internetmaps/index.html)
  ESRI's Internet Map Server (IMS) solutions provide the technology for developing Web mapping applications ranging from finding directions to mapping biodiversity to creating the Geography Network. Within the website, you can explore the live Internet Map Server demos to see the breadth of application using ArcIMS covering the fields of education, climate mapping, spatial analysis, demography, environmental mapping, health, tourism, etc. You can also visit web sites powered by ESRI's Internet Solutions to explore the functionalities provided by the ArcIMS.
  
  
• GeoMedia ActiveX Viewer (http://www.intergraph.com/gis/gmwm/)
  GeoMedia WebMap, the product of Intergraph, is a Web-based visualization tool that offers real-time links to GIS data warehouses. You can query a database and see information in the form of a map. You can also click on a feature and see selected data behind that map. The Uniqueness of the WebMap lies in its support of open standards and customization, its provision of dynamic analysis. Following this link, you can explore the specifications of GeoMedia WebMap and product demos to get fresh ideas on how the WebMap works and how can WebMap serve specific purposes. If you are interested in the products, you may sign up and have free online training now! The training focuses on the topics of data capture, data access, raster handling, analysis and presentation. (The ActiveX viewer was deactivated.)
  
  
• Visa ATM Locator http://www.visa.com
  This website provides comprehensive introduction of Visa cards, one of the most popular used credit card in the world. The most interesting thing about the website is that you can select the region which will link to the countries that you can choose to go to specific country for detailed information. It is developed using the javascripts. Can you call it a web map? Yes or No? A good example that leads you to think of what is web-based mapping.

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