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DEVELOPING AN INTERNET-GIS APPLICATION USING GML 
TECHNOLOGY 
Ali Asghar Alesheikh *, Ehsan Mohammadi ™*_ Ali Aien ©, Hossein Mohammadi ¢ 
; " PHD in Geo-Spatial Information Systems, Dept. of GIS Engineering, Alesheikh@kntu.ac.ir 
M.Sc. Student in Geo-Spatial Information Systems, Dept. of GIS Enginecring,mohammadichsan@yahoo.com 
* M.Sc. Student in Geo-Spatial Information Systems, Dept. of GIS Engineering, ali_aien(@yahoo.com 
“ M.Sc. Student in Geo-Spatial Information Systems, Dept. of GIS Engineering, hoseinmohamady@yahoo.com 
abes Faculty of Geodesy and Geomatics Eng., K.N. Toosi University of Technology, Vali asr St, Mirdamad 
Cross,Tehran, Iran, P.C. 1969715433 
Tel: +98 21 8789357, Fax: +98 21 877 9476 
  
KEYWORDS: Web-based, Internet, Interoperability, visualization, standards, spatial infrastructure 
ABSTRACT: 
Spatial Data as one major component of every GIS System has faced many challenges these years. Each software uses its own data format 
and exchanging from one format to another may cause some problems like lose of data or incompatibility. Going toward Interoperability 
and inventing open data formats will help data owners to prepare their data for all users with different needs and different software. Markup 
languages with their characteristics made it casy to define any kind of data without the need to have any particular software. So spatial data 
is no exception. Using new technologies like XML and GML helps to find a way of Interoperability and data sharing, with the benefit of 
independency of any special software. 
  
1. INTRODUCTION 
Since its dawn GIS has been developed rapidly as a science, 
found too many applications as a tool, and helped managers and 
organizations to reach their purposes as a Decision Support 
System. The main components of a typical GIS are: Hardware, 
Software, Expert user, Analysis and Spatial Data. 
Spatial Data plays a vital role in a GIS system. The best 
explanation of real world data gives, the more reliable results 
GIS presents. Thus dozens of data formats have been developed 
for the digital encoding of spatial data and information till now. 
Many are proprietary to specific software. A few are open 
standards created to enable transfer of spatial data between 
different vendors. But no scheme for interoperability based on a 
common format was produced successfully. As a result of this 
falue, OGC (Open GIS consortium) formed in 1994 to 
develop a new interoperability approach based not on formats 
but on open, common software interfaces. 
OGC's OpenGIS Specifications for interfaces and protocols 
have become widely used and are the foundation for 
interoperable geoprocessing. Beside the progress of OGC, the 
arrival of the World Wide Web Consortium's XML, presented 
4h opportunity for a new common geodata format, GML, to be 
developed in OGC. 
2. WHAT IS XML? 
XML is a universal format for structured documents and data 
On the web and has been a W3C standard since 1998. XML 
brings a new way to deal with data and information. It allows 
developers to specify rules for designing text formats for any 
data in a way that produces files that are easy to generate and 
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read, that are unambiguous, and that avoid lack of extensibility 
and platform-dependency. 
In traditional data exchange formats, data is defined by the 
position it takes in the file structure. But in XML the position of 
the data is not important. Instead, tags identify or define the 
data content. Like HTML and their mutual parent, SGML 
(Standard Generalized Markup Language), XML works on the 
principle of tags, which delineate elements and content. For 
example the XML document in listing 1. uses tags to describe 
the properties of a phone. 
Listing 1. 
<?xml version="1.0"> 
<phone> 
<number> 7273166 </number> 
<owner> Ehsan </owner> 
<position> Zanjan </position> 
</phone> 
This simple document has four elements: phone, number, 
owner, and position. These elements are indicated by tags, or 
constructions that start with the less-than sign (<) and end with 
the greater-than sign (>) surrounding the name of the element. 
XML in its broadest form can be regarded as a universal 
language for describing structured information. Structured 
information can be anything that contains both content (words, 
images, tables and so on) and markup, which is the additional 
information that describes the content and gives it a definite 
meaning (table header, number, owner and so on). XML 
defines a standard syntax for describing a documents content 
through the use of markup tags.[Kim, 2003] 
The XML specification provides a standard way for defining 
markup languages for textual documents. lt is a meta-language 
that allows users to design and format the structural