Llido & Suarez

The Use of a Gateway to Operate in a Remote Database by Using the WWW

Dolores Maria Llido¹ and Juan Claudio Suarez²
¹LISITT (Laboratorio Integrado de Sistemas, Inteligentes y Tecnologias de la Informacion en Trafico), Universitat de Valencia, C/ Hugo de Moncada 4 Entlo. Izda., 46010 Valencia. ESPANYA
²Forestry Commission

Abstract
The World Wide Web (WWW) was originally developed at the CERN in Switzerland as a way to give common interface to the existing communication protocols in the Internet and all the different ways of data exchange formats. The WWW is one of the most efficient mechanisms of information exchange through the Internet because its multimedia configuration.

The WWW uses a protocol called http (HyperText Transfer Protocol), that allows the transfer of coded representations in MIME (Multipurpose Internet Mail Extensions) between client-server. The WWW is increasingly becoming a service of information exchange based on the use of a hypertext language known as HTML (HyperText Markup Language), which is a subset of Standard Generalised Markup Language (SGML). In a document made in HTML, words can be connected to other documents by means of quotations that redirect you to other pages where some other information is displayed. The WWW is configured in an architecture client-server where the client connects to the server by means of a URL (Universal Resource Locator).

The WWW may also be used for databases queries. The user communicates with the system by filling a form. These forms are interpreted by a CGI script (Common Gateway Interface) which translates to the system the user request. A graphical type of CGI interface is known as Image maps. This system allows the use of Hyper-regions within an image which may be easily selected by the user by a mouse. Each region will connect the user with another location in a similar way as the Hypertext does.

This paper describes the design of two different gateways to allow a remote user gaining access to ORACLE database and ARC/INFO Geographical Information System. The advantages in the use of the WWW as a user interface are:

the access to the system to users with limited computer knowledge.
the visualisation of documents with text and graphics.
the interaction of the different packages by means of CGI's.
the access to any kind of information just by clicking with the mouse on text or the region of a map.
an open access to the system by everybody with simple computing facilities. The special configuration of the system can incorporate routines of data protection, restricted access and security by means of a server manager.

In the ORACLE-WWW Gateway, it has been used a database about traffic. The CGI is structured in three parts:

Use of FORMS to capture the entry parameters to the database from the Web-client.
Consultation to the database by means of SQL sentences.
Return of the results of the consultation to the Web-client by using an HTML page.

In the GIS-WWW Gateway, the interface creates a possibility for the user to visually select a page from the original map with the mouse. The user also can select a coberture and magnify the display by means of buttons. The innovation of this gateway is the possility of handling graphic information in an intuitive way. This means that the user can select a specific area of interest within the map by just defining a square with the mouse instead of typing co-ordinates. This approach may benefit applications where the exploratory search of data is required like in contiguous areas in different maps at any level of resolution.