A Comparative Assessment of Internet GIS Server Systems
MapInfo MapXtreme Java Edition 4.0
MapInfo MapXtreme Java Edition is a 100% Pure Java enterprise mapping server designed that should, in theory, properly work anywhere. Java-based mapping applications allow developers to write a single program using on multiple platforms that support virtual machines (MapInfo, 2001, URL). MapXtreme provides mapping functionality in the form of JavaBeans for easy drag and drop development in a visual IDE that cooperative with novice Java programmers. For experienced Java programmers, the MapJ API was used to programmatically design. The MapJ API is the client-side API used to communicate with the mapping engine, MapXtremeServlet. MapXtremeServlet behave as a key element of this product, a server-side component that manages the requests and responses for mapping services, including image requests (GIF, JPEG), vector data requests (query methods), and metadata requests (table information). It is compatible with all J2EE-certified Web servers/ browsers, and there is no proprietary plug-ins. There are four high-level components: the MapJ object, map Renderers to display maps, Data Providers to access various data sources, and MapXtremeServlet (MapXtreme Dev Guide, 2001). The component-based architecture makes MapXtreme flexibility to deploy in any web system architecture design. It is compliant with web server supporting ISAPI, NSAPI, or CGI gateways, such as Netscape, Apache, or Microsoft Internet Information Server.
Some requirements are necessary for implementation of the mapping applications with MapXtreme. In general the web server must be obliged to supports servlets/Java Server Pages or integrate with plug-in to support servlets/JSP's or stand-alone servlet container which is J2EE compliant such as TomCat, IBM WebSphere, iPlanet, and others. Furthermore, in the thick-client architecture that puts MapJ on the client-side. It is possibly to receive map in vector data and display maps from these vectors by additionally add the Java Virtual Machine plug-in on the browsers.
ArcView Internet Map Server 1.0a
Environmental Systems Research Institute Inc. (ESRI) has created several products to enable developing Webmapping applications for the Internet. ArcView Internet Map Server (AVIMS) comes as an extension for the desktop GIS software program ArcView GIS. Due to its integration with the core ArcView GIS software itself, the spatial visualization of the Webmap and the functionality of the Webmapping application in general is determined to a great extent by the capabilities of ArcView GIS. There are three components in AVIMS, first is Internet map server extension that enables an ArcView session to communicate with the internet via the web server. For enables the web server to communicate with the ArcView, the ESRIMap web server is required. This is compliant with ISAPI (Internet Server Application Programming Interface) and NSAPI (Netscape Internet Server Application Programming Interface). Ultimately, the component that provides the basic tools for browsing, exploring and querying maps is MapCafe Java applet.
To tackle the vector-raster barrier between GIS and the Web, ESRI takes a server-side approach: it uses vector and raster data for geo-processing, but uses raster images (GIF or JPEG) for display purposes (ESRI, 1997, URL). By default, AVIMS uses the JPEG format, but GIF support can be provided. There are several ways to customize the AVIMS Webmapping pages. The fundamental way is using the Avenue script which is the general ArcView object-oriented programming language and develop environment. The scripts allow you to control how the AVIMS serves your maps. Usually, Avenue working on the system scripts that build up the personal working environments so as to manage the communication between Arcview and the ESRIMap web server extension. For modifying the user interface including layout, the embedded tools and buttons, AVIMS make available by a Java applet called MapCafe (ESRI, 1997). This Java-based applet provides a ready-built GUI for displaying Webmaps in a standard Web browser. When users visit the Webmapping application, the applet downloads automatically from the Web server onto the client-side to be interpreted by the Java Virtual Machine (JVM) of the Web browser. Users do not have to install anything on their system before they use the Webmapping application.
MapServer 3.6.1
MapServer is an Open Source development environment for building spatially enabled Internet applications. MapServer is known to compile on most UNIXes and will run under Windows NT/98/95 and absolutely run on Linux/Apache platforms. MapServer generally runs as a CGI application from your http server. This holds true unless you are building a more advanced application with MapScript, which accesses the MapServer API directly. The logic of a MapServer Application is demonstrated in three core components that are the Mapfile, the template file and the GIS dataset. The Mapfile defines the data to be used in an application and display and query parameters accepted as the application's configuration file. The Mapfile also includes information about how to draw the map, the legend, and maps resulting from a query. The template file controls how the maps and legends output from MapServer will appear on an html page. It operates like any other HTML file except that certain fields can be modified by the MapServer CGI. Mapserver uses ESRI shapefile format as its default vector file format. Raster data can come in several different formats, depending on how MapServer is compiled. By default, MapServer supports geoTiff files and Tiff files with world files (MapServer,2002, URL).