Html and Multimedia Web Gis Tariq Rahim Soomro, Kougen Zheng and Yunhe Pan Department of Computer Science, Zhejiang University, Hangzhou 310027, P.R.China.
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Abstract HyperText Markup Language (HTML) is a platform-independent method of identifying a document's structure and references. Web is a distributed hypertext multimedia information service that brought millions of non-academic and academic users to net. While in contrast to traditional GIS, multimedia Web GIS is not only able to collect, analyze and store the data in traditional formats i.e. text, images (pictures) and graphs but also audio (sound), animations and video (moving pictures) as well, using all the techniques, advantages and multimedia facilities of Web. In this paper, the multimedia data along-with the advantages of multimedia GIS (MMGIS) over traditional GIS are explained. HTML plays a robust role in the development of the multimedia Web GIS. Through HTML our multimedia Web GIS can be viewed into three different categories. These are Static Web GIS, Dynamic Web GIS, and Active Web GIS. These three broad categories are also discussed briefly in this paper. Key Words: GIS, HTML, Multimedia, Web, MMGIS, Web GIS.
1. Introduction HyperText Markup Language (HTML) is a platform-independent method of identifying a document's structure and references. It acts as a source code for Web (native language of Internet). It is a combination of variety of elements called tags, which are used to define type styles, headings, inserting specialized contents such as images, sounds, virtual reality words, Java applets and many more. The term multimedia is defined as “A multimedia system is characterized by computer-controlled, integrated production, manipulation, presentation, storage and communication of independent information, which is encoded at least through a continuous (time-dependent) and discrete (timeindependent) medium” [1]. There are several ways to define Multimedia GIS (MMGIS) such as “Multimedia GIS is the combination of the use of GIS to georeference, structure and analyze these data and the creation of multimedia presentations with links to spatial features” [2]. Or a definition by Laurini and Thompson as “Multimedia GIS is a variety of analogue and digital forms of data that come together via a common channel of communication” [3]. The term Web GIS is defined as the media, where GIS is available, using all the techniques, advantages and multimedia facilities of Web. In other words, one can say “GIS found on Web, with power of Web”. GIS on Web is one of the popular fields and numerous sites (commercial & non-commercial organizations) have added GIS (or GIS related) information on their Web sites [4]. User can view many kinds of maps (2D to 5-D –row, column, level, time and an index into a set of physical fields http://www.ssec.wisc.edu/~billh/view.html) [5]. Integration of Multimedia and GIS can be viewed as follow [2, 6].
a. “GIS in Multimedia”: this approach uses multimedia-authoring tools to blend different data types (text, image, video, audio) and spatial analytical function to boost traditional GIS or in other words MM has capabilities to incorporate GIS. Web GIS is the best example of GIS in Multimedia. Web is a distributed hypertext multimedia information service, which enable GIS to equipped multimedia facilities. a. “Multimedia in GIS”: In this approach the traditional GIS will encompass the capabilities to take care of multimedia or in other words GIS has capabilities to incorporate MM data types. This paper is written, keeping in mind the importance of HTML, because when we are talking about Web/Internet GIS, we are talking about HTML. Particularly, this paper is not about the HTML nor is it about the multimedia Web GIS, but this paper will discuss the role of HTML in designing the multimedia Web GIS. In other words, this paper is about the integration of HTML, Multimedia (MM), Web/Internet and GIS. It will benefit the researchers and users to understand the power of HTML in designing the multimedia Web GIS. The next section of this paper covers MM data types and advantages of MMGIS over traditional GIS. Then we categorize the multimedia Web GIS into three broad categories defined in the form of Static Web GIS, Dynamic Web GIS and Active Web GIS. Further, designing of Active Web GIS through ActiveX Controls and Java Applets is also discussed.
2. Multimedia data
From past to present, spatial data have been gathered, analyzed, displayed in analog form, and latter in digital form. Nowadays simple digital form called multimedia form is very popular and widely used. From HTML point of view, Multimedia on the Web is divided into two basic categories- things that can be displayed in-line or as an integrated part of the browser (internal), or contents that is handled outside the browser (external). Implementing both plug-in content and external applications requires the user to have the necessary software already installed on his/her system. HTML 4.0 allows the tag to encompass all internal content. The version of could apply to applets, plug-ins, ActiveX, images and any future type of embedded [7]. Following subsections will discuss these media. 2.1. Text Text is generally the common way to represent data in computer. HTML helps to view the text in a variety of forms such as providing different fonts, and their different sizes, different color schemes with text alignments and formatting and so on. Some browsers (e.g. Internet Explorer) allow you to view scrolling Marquees (e.g. TEXT ). 2.2. Images Images are one of the simplest forms of visualization using multimedia data, either produced by scanning existing photographs, or captured, directly from videotapes etc. HTML helps to view basic images; background images, and also allows viewing the maps as ismap for Server-Side Maps and usemap for Client-Side Maps. HTML allows Common Gateway Interface (CGI) to incorporate image maps. CGI Scripts can be used to handle input
from image maps. This input is different from the input that an HTML form sends. With the help of CGI, static and dynamic map can be handled. Handling static data is usually easier because the meaning of the user's selection can be determined early in the decoding process. Dynamic maps require the user's selection to be interpreted late. Image maps allow different regions of an image to be mapped into different URLs (Uniform Resource Locators) that are retrieved when the region is clicked on. These URLs can be for an HTML document, an image, a CGI Script, or anything else that can be referenced from the Web. Dynamic image maps or images in general can be defined as clickable images so that they return the user's chosen coordinates (x,y) to any CGI Script. These images do not need to create a map file but must have a script that is able to handle the coordinates and process the request [8]. 2.3. Audio Audio was the first step towards today’s multimedia capabilities. Now sound and music are common addition to MM tools and MMGIS applications to help simulate reality. HTML helps to listen sound (sometimes in the form of oral presentation) background sound and music. An HTML standard allows two ways to incorporate multimedia contents. The first approach is Java and the other approach is indirectly supported by HTML through its
tag. Java Animator Applets can be used to add animation and sound to any kind of Web page. HTML support tag to include Java Applets. The basic syntax to include Java Applet is:
2.4. Video Videos and animation are the more complex form of visualization. This form of representation offers considerable advantages in terms of providing sense of place. Video offers tremendous potential to draw a viewer into a virtual world. HTML helps to view video clips and animations as we mentioned in the above subsection by using Java and HTML's
tag.
3. Advantages of multimedia gis a. MMGIS has full capability to provide services to both technical and non-technical users. b. MM provides such an atmosphere in which user feels comfortable with the system environment before addressing the issues of data analysis. Basically, MMGIS allow user to interact with datasets and help to increase his/her understanding of these datasets [9]. c. Users of the MMGIS will retain more knowledge than users of traditional GIS. d. MMGIS allow traditional data in the electronic or digital formats and allow updating the data easily and efficiently with low cost [10]. e. MMGIS is also capable of improving procedures for data collection, accuracy & management of temporal data, and understanding of the computerized tools used to handle uncertainty in digital spatial database [11]. The combination of audio and video along with traditional data types can improve the performance of GIS turning it into a more realistic tool for spatial
analysis. Video can be used to show background, point scenes, or transition and audio to provide realism by communicating the notion of space. This will allow more clear and transparent view of overall situation and better understanding of its spatiotemporal implications, because of accessing to additional source of information. MMGIS can possibly create multiple representation for same phenomena. This characteristic enables the users to view same information in several different contexts [12].
4. Categories of multimedia web gis HTML plays a robust role in the development of the Multimedia Web GIS. On the one hand, HTML provides limited facilities (in forms of limited tags) to incorporate multimedia and GIS, but on the other hand, HTML provides unlimited facilities, in the form of its capabilities to incorporate applets, plug-ins, ActiveX, and future type of embedded. Through HTML our multimedia Web GIS can be viewed into three different categories. These are Static Web GIS, Dynamic Web GIS, and Active Web GIS [13][14]. 4.1. Static web gis Web GIS, enable GIS user to manipulate GIS data and maps on the Web interactively. The users can browse the Web page through the hypertext linkage. Each Web page is a static image organized by the Web developer. Static pages are static HTML pages that are prepared in advance of the request. A geographical document from a static Web GIS is stored as a file and its contents are determined (and fixed) by its author when it is created. The GIS Server returns the HTML pages to the user, but takes
no special action. The user requests a static page by typing in an URL or by clicking a link pointing to an URL. The URL request is sent to the GIS Server. Therefore, each request for a static multimedia map documents results in exactly the same response. Strictly speaking, this should not be called GIS at all, for it lacks the ability to analyze geographical data. Figure 1.
Figure 1. Static web gis 4.2. Dynamic web gis GIS also can take advantage of Web’s dynamic ability. Dynamic pages are created in response to a user’s request. A multimedia geographical document from a dynamic Web GIS is not stored as a file, but created by a dynamic Web GIS whenever a browser requests the document. Because a fresh multimedia geographical document is created for each request, the response of a dynamic Web GIS varies from request to request. A Web browser collects information by presenting a page with text boxes, menus, or check boxes that the user fills in or selects. When the user clicks a button on a form, the data from the form is sent to the GIS Server. The GIS Server either passes the data to a script (CGI, Pearl) or application (Internet Server Application Programming Interface (ISAPI), Internet Database Connector (IDC)) to be processed or it queries or posts data to a database. The GIS Server returns the results dynamically to the user in an HTML page. Each time user accesses the site he/she
will view the different information (depending on their request). Web GIS is dynamically linked with the sources. This dynamic linkage with the sources always keeps the data and software current. On the server site, the CGI (Common Gateway Interface) script will be responsible to provide real-time multimedia information. Web GIS can link with multimedia real-time information by real-time connection with the relevant information sources. Figure 2.
Figure 2. Dynamic web gis 4.3. Active web gis A geographical document from an active Web GIS is not fully specified by the server, but a computer program that can run on the browser’s local machine, can interact with the user and change the display continuously, and can use the multimedia geographical data at the server. When a browser requests an (active) map document from an active GIS Server, the server returns a copy of the program and then the browser runs it locally at the client machine. HTML allows creating active documents through a number of ways such as ActiveX Controls, Java Applets, JavaScript, VB Script, and so on.
4.3.1. Active control web gis: HTML allows ActiveX Controls to create any user-defined Controls. One way to develop multimedia Web GIS is the use of ActiveX Controls to create GIS Controls. ActiveX is developed by Microsoft to “activate the Internet”. An ActiveX Control is a program, or an executable file that exposes certain methods, properties, and events through a programmable interface. An ActiveX is a modular piece of software that performs tasks and communicates information. It can be used and reused by any program or computer language that is able to contain ActiveX Controls, such as Web browser, for example, Internet Explorer and Netscape Navigator (with certain plug-ins installed) or languages, for example, Visual Basic, Visual C++, FoxPro. GIS Controls have computational power, communications power, and powerful graphic interface, and can be used like plug-ins and Java applets within Web browsers. There are many sorts of ActiveX Controls for different capabilities and functionalities to handle GIS data and perform GIS analyses. The MapObject Internet Map Server (http://www.esri.com/) and GeoMedia Web Map server (http://www.intergraph.com/iss/geomedia/) adopts the GIS ActiveX Controls approach. 4.3.2. Java applets based web gis: HTML allows incorporating any kind of applet as a part of HTML document. Java applets based Web GIS is the most recent flavor of multimedia Web GIS. Java applets are mini applications that run inside a Java enabled Web browser. Java applets are executed on a client site on demand. It provides a wide range of tools for creating and displaying graphics, and manipulates GIS data on the Web. Each GIS function for example zoom in, zoom out, query, label and the report of query output etc. could be one separate Java applet.
No system can guarantee 100% security; Java goes a long way to ensure the protection of client system from applets [7]. ESRI’s ArcView Internet Map Sever (http://www.esri.com/) and ActiveMaps by Internet.com (http://www.internetgis.com/) are using Java applications on the Web.
5. Conclusion It is important to understand that spatial incorporation is not easy. There are many hurdles to incorporate spatial information. Especially, when we are talking about spatial information on Internet, we need to understand HyperText Markup Language (HTML) the native language of Internet and the parallel advance technologies for example ActiveX Controls, and Java Applets etc. HTML itself has limited resources to incorporate multimedia and GIS (in the forms of built-in tags), but it has capabilities to incorporate, applets, ActiveX Controls, and other future incoming inventions. So, even at this stage, the future of multimedia GIS is bright, using HTML, as a basic language and Java Applets and ActiveX Controls as advanced techniques within HTML.
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