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The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics
Chen, Jun

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
Xingling WANG Chongjun YANG Donglin LIU
Institute of Remote Sensing Applications, Chinese Academy of Sciences
P.O.Box 9718, Beijing, China 100101
Tel: 86-10-64889212 Fax: 86-10-64889206 Email: wxl@digitalearth.net.cn
KEYWORD: XML, Web Mapping, GML
XML (extensible Markup Language) provides a powerful new way for data description and data exchange, and it is becoming widely used
on the World Wide Web. Over 100 XML derived languages emerging in last year. In March of 2000, OpenGIS have proposed a format to
represent geographical information with XML, which is called GML (Geography Markup Language). GML is a powerful new way for
geographic information sharing, interoperability and Web Mapping. This paper represents a GML-based Web Mapping application that
public spatial data via the web. The new web will be a semantic web. With GML, spatial data will be integrated within the semantic web
XML is the “extensible Markup Language” that was
developed by the World Wide Web Consortium. XML is an idea
data format for storing structured and semi-structured text
intended for dissemination and ultimate publication on a variety
of media (Robin Cover, W3C 1998). Over 100 XML derived
languages emerging in last year. There are two subtle but
keenly important differences between HTML and XML.
SoftwareAG (makers of Tamino, an XML based database)
explains the distinction this way: The motto of HTML is: "I know
how it looks," whereas the motto of XML is: "I know what it
means, and you tell me how it should look.“ Said another way,
HTML is about making pretty presentations while XML is a
semi-structured document that holds "content". Various
techniques based on the XML are under an intensive
development by the World Wide Web Consortium (W3C).
In the world of GIS we are still a ways off from extensive
adoption of XML, as researchers and vendors explore and
define how XML will be used (Adena Schutzberg, 2000). ESRI
has chose XML to store metadata in Arclnfo 8. The data is in a
raw format, and depending on your needs can be displayed in
different ways. Gl, Geographic Information, community's
interest in this new technology is exemplified by the various
initiatives to adopt XML syntax as a encoding language for
spatial data. Examples include the ISO TC211's work on
developing rules for expressing UML-modeled datasets in an
XML vocabulary and the Open GIS Consortium's (OGC)
recently introduced Geography Markup Language (GML). The
W3C is also developing an XML-based Web vector graphics
specification, called Scalable Vector Graphics (SVG). Since the
number of XML-encoded spatial datasets available on the Web
is evidently going to increase, a question must be raised about
how these datasets might be used. Many client applications will
not be able to process spatial information in it's original form.
The W3C's recent Recommendation, extensible Stylesheet
Language Transformations (XSLT), is a power tool to
pre-process spatial XML-based datasets into a more
easy-to-use form.
Web Mapping is the set of products, standards and
technologies that enable access to location information, usually
portrayed as maps, via the Web(OGC, 2000).
Unfortunately, today, most Web Mapping applications are
inseparably tied to a specific server implementation. In other
words, the client is hard coded to interact with a particular
vendor's proprietary map server implementation. User must run
different client applications in order to access the data and
functionality provided by different server implementations. In
this situation, there is very little interoperability or reuse of client
and server implementations. Because data are often accessible
only through a given server, there is also very limited ability for a
user to transparently access data of interest from outside a fixed
The Open GIS Consortium's Web Mapping Testbed (WMT) is
a process that brings together sponsors (customers) and