by W3G - (The World Wide Web of
What is Geotech-XML? Geotech-XML (or simply GML)is the Geotechnical Engineering application of the new Web language, XML. XML is described in the next paragraph, but it can be thought of the new generation of HTML, especially designed for tranmission of data over the Web. Basically, Geotech-XML introduces geotechnics-specific tags so geotechnical data can be easily represented by simple files with features such as:
- Easy to generate,
- Easy to understand by people,
- Easy to interpret by programs, including browsers,
- Tools are already available or easy to develop.
A simple example of Geotech-XML is:
soil="silty sand X"
<soil name="clay A">
What is XML?
XML is eXtensible Markup Language, the new-generation Web technology for representation and transmission of structured data over the Web.
XML is a newly approved standard for Web documents. XML can be seen either as a big improvement over HTML (the current Web page language), or a simplified version of SGML (Standard Generalized Markup Language), ISO 8879 by the International Standards Organization(ISO). Although SGML has been around for a long time it has never become popular mainly due to its complexity. Its much simpler version, HTML, has established itself firmly as the Web-page-language. However, HTML's limitations are recognized by everyone whenever one attempts to either (1) improve the presentation or (2) preserve the structure of the data presented. These limitations have lead to the introduction of numerous new tags by browser makers which do not work on other browsers. Adding browser-specific extensions to HTML is an ongoing problem rather than the solution to the limitations of HTML. The SGML Editorial Board at W3C has been searching for a solution. It has recently been reorganized
as XML Working Group, emphasizing the extensibility aspect of the new standard.
XML is extensible because it is a metalanguage, which enables someone to write a Document Type Definition (DTD) like HTML 4.0 and define the rules of the language so the document can be interpreted by the document receiver. The purpose of XML is to provide a language that allows for custom tags to be processed.
Custom tags enable the definition, transmission and interpretation of data structures among computers on different platforms. XML separates data form its representation or appearance, something that HTML combines in one set of tags. XML has its own style language, XSL (eXtensible Style Language). This is the approach adopted in the most recent version of HTML (4.0).
XML is ideal for developing Web presentation and transmission techniques for geotechnical data because of the extensibility and other features of XML. Database applications are available (or easily adaptable) using the existing browsers. Since geotechnical data are stored in a large variety of hardware and software systems, a common standard for data interchange is clearly beneficial for all.
Web Resources on XML
A wealth of authoritative information on XML can be found at these Websites for those who want to learn about XML:
Who Uses XML?
XML has already been adopted in the following fields (this is by no means exclusive):
- MathML Mathematical Markup Language, which describes formulas and equations in a web page, without bitmapped images, is an XML application
- CML Chemical Markup Language, which describes molecules and other chemical symbols in web pages without bitmapped images, is another early XML application
- MusicML: A XML Experience is an interesting application of XML in which Java is used to render the parsed MusicML document representing musical notation as a non-GIF image.
- Microsoft uses XML in its CDF, Channel Definition Format which it uses for its "push" technology
- Microsoft announced that the next version of Microsoft Office will use XML to represent the various Office-specific formats. Users will be able to save Office documents as HTML, modify them in the HTML domain, and then import them back into Office due to XML as the intermediate format.
- Java applets and scripts for database publishing are already available as simple examples in XML textbooks
- Web automation by WIDL (Web Interface Definition Language) employs XML.
- The OFX Standard (for Open Financial Exchange) had started out as an SGML application, but currently being converted to an XML application; it is a joint project of Intuit, Microsoft, and Checkfree Corporations. Financial institutions are developing their end for secure financial data interchange using XML based standards.
- Last but not least, XML for geotechnical applications, or GML or XML-G, is being developed.
Web Browsers and XML
There is an "experimental" browser from W3C, Amaya, that now accepts XML. Microsoft IE 4.0 already has support for XML, and the next version of Netscape has been announced to follow. There are many Java sripts (or the international version, ECMA Scripts) available in the literature and several commercial applications have been (and are being) developed for use in XML applications.
How to Contribute to Geotech-XML
Until Sept. 1998 only a few basic steps were taken in the development of the XML for geotechnical applications. Due to the built-in extensibility of the language, its development may never end, but it will certainly mature in a few months or years. One of the main advantages of XML is that it will be the international standard for "exporting" data files from geotechnical software. Therefore, eventually, all geotechnical software will "understand" GML documents.
Current Status (May 2002)
The GML Steering Group of
W3G has approved the proposed
Core Tags with the attendant
DTD file and the
developed by J. D. McPhail and M. Oner. Read a white paper by JDM:
Building of the GML Core (599k PDF file) also see the Powerpoint presentation Principles on which GML Core is based (1.8MB PPT file)
Dr Toll's GeotechML applications (includes Java applet for plotting boring log data)
Representing slope stability case histories (SlopeSML at Istanbul Technical University)
Java applets and scripts will be posted at the EJGE and Geotech websites as they are received from the developers.
Current GML Group members can be seen
in this page.
W3G members who would like to contribute to this effort please contact Mete Oner by email and express their desired level of involvement in developing the standards.