Ubiquitous GML

Friend or Foe - GML is Here to Stay

Whether you hate or love the concept of GML, the technology is here to stay.

As more and more GML datasets are being introduced – specifically across Europe – GIS professionals are having to learn the benefits of this new standard. GML 1.0 was introduced in May 2000 as a new format to express geographic information. Now on revision level 3.1 and a formal ISO standard (ISO 19136:2007), GML is fast becoming the de facto method of sharing and transporting descriptions of objects in the world around us.

Figure 1: A view of the IMRO Schema in Snowflake’s GO Loader - the GML Loading tool.

Just Another Standard

None of us could possibly contemplate traveling across Europe today without being able to use our mobiles. We have all grown used to landing at Amsterdam or Frankfurt airport, switching on our faithful friend and being “welcomed” to the local network. This would not be possible, however, if the communications industry had not been through the same tortuous experience of standardization nearly 30 years ago. We are now used to services from former “localized” suppliers to interoperate seamlessly. Of course standardization also encourages competition which, in turn, drives down costs but that is a subject for a further article. So, if communications can cross borders, it is surely to be expected that geographically referenced data should be shared across borders too. Standardization to GML facilitates this task.

GML Today

Currently, the widest implementation of GML within Europe is represented by OS MasterMap® - 450 million 1:1250 scale features introduced in Great Britain in 2001. At first, many users and vendors complained as they missed their traditional GIS formats. However, a few months later (together with some late night software development), GML has become just another format, another button on a menu and a ‘done deal’.  Whilst people are always cautious of something new, the reality is that GML is not complicated - in fact its just data in a plain text file, pure and simple and that’s the beauty of it. In the Netherlands, several GML datasets are now emerging under the NEN3610 basis geo-information model including: IMRO 2006, IMKICH, IMWA and IMBOD to name just a few. Further details on the technology and development of GML can be found in Huibert-Jan Lekkerkerk’s article “GML - Geography Markup Language” in the October/November issue of Geoinformatics 2007.

Why GML?

With all these new GML datasets appearing in the Dutch market, it is interesting to see the same issues and concerns being raised. GML is undoubtedly different to existing GIS formats and, being very honest, can sometimes be difficult to work with using current GIS technology. However, it is important to understand the future benefits that GML will bring to the industry and why it is important for organizations to begin working with GML. 

Firstly GML is XML, the ubiquitous data exchange language of mainstream IT.  Since 1998, when XML was adopted as a W3C standard, IT systems have communicated with each other in an open manner using XML.  Microsoft, Oracle and IBM have all invested huge resources into developing XML to solve system to system interoperability and data exchange, so why does the GI industry not take advantage of this investment?  Spatial data is not different - in reality it is just data.

No matter which GIS conferences you attend, you will always hear at least one speaker state ‘GIS is going mainstream’. In order to achieve this aim, GIS will need to exchange data in an open and standards’ based manner. GML is just XML is just data - and can be read by the same tools used to read business data. GML is truly taking GIS towards ‘mainstream’, which why we need to make everyeffort to adopt and work with it. Failing this, GIS will always be the sad geezer at the party who sits in the corner and talks to nobody!

It’s Nothing to be Scared of – View GML for Yourself

We all know our GIS formats. They are familiar and tangible, whereas GML, XML and XML Schema can all be a bit daunting.  But it really does not need to be that way. And there is no need to dive head first into the vast sea of GML. You can test the water first. Snowflake Software has been working with and advising on all good things GML since the company’s inception in 2001. Realizing early on that the concept could be overwhelming, Snowflake introduced a GML viewer that helps take the fear out of GML.

The viewer is a self contained tool with free sample data sets that enable you to get familiar with GML. Because the viewer is based on generic GML (which, after all, is the concept of a technology standard in the first place) it can read any GML dataset – you can even use it to display a GML schema you are developing yourself.

The viewer enables you to load data, select and view features and their properties (elements in GML that are used to describe features) and display and hide GML layers. It is the perfect tool for becoming familiar with GML and some of its capabilities – before progressing to the real thing.  

Snowflake Software.

The GML Viewer at a Glance:

• Reads any GML 2 or GML 3 application schema
• Provides in-built style support for IMRO2006, TOP10NL, AAA-NAS and OS MasterMap
• Reads WinZip, GZip and uncompressed GML files, up to 1900 features / second
• Loads multiple files into a single view
• Supports the saving and loading of user defined styles
• Enables the display of feature attributes and compares attributes of multiple features (Feature Attribute Browser)
• Displays the number of features for each feature type loaded (Feature Statistics)
• Displays by Attribute - displays features by attribute and/or a combination of attribute values
• Enables single and multiple feature selection
• Provides multiple Views - dockable windows supports tiling and iconifying
• Supports position tracking - showing X,Y of cursor position
• Provides navigation and zoom in/out facilities

About Snowflake Software

Snowflake Software was founded in 2001 with the vision of making GML easy to use and, hence, achieve its objective of being truly ubiquitous. As well as the free Viewer, Snowflake Software also provides a set of loading and publishing tools to make working with GML easy and efficient. The company also has a GML Consulting team and provides GML Fundamentals and Hands-On Training. The GML Viewer is free to download at www.snowflakesoftware.com.

Elizabeth Wilkinson is Head of Sales and Marketing at Snowflake Software

elizabeth.wilkinson@snowflakesoftware.com

www.snowflakesoftware.com