XML Schemas are descriptive documents which are used to define the format of information. For the purposes of our work here, they allow us to create data structures (instances) which can be used to exchange nutritional information. This means that, for example, data on the nutritional content of foods can be imported and exported from diverse systems. Therefore, we can

• Import data from manufacturers, government agencies and other suppliers
• Transfer data easily between different software products
• Generate datasets in an approved, internationally acceptable and unambigouous format

This page is an introduction point to various approved XML Schemas used to define nutritional data. It includes the schemas themselves, instance samples, access tools and descriptive texts. Currently, the first schema, for the nutritional composition of foods and recipes, has been approved and is on the UK e-Government website. For details, click the link in the left hand panel. For general information on the UK e-Gov website, click here (www.govtalk.gov.uk).

Background

The XML (eXtensible Markup Language) data format is a text-based format used to contain information in a structured way. That is, an XML file (called an instance) contains named marker pairs like HTML. Between these pairs, data can be held. The file can be interpreted both by computers and (by viewing in a simple text editor) by humans. An XML Schema is a document which describes an XML instance. It declares data types, names, ranges, etc., for the data as well as showing the structure of the data. It can include validation checks and additional information which assists either computers or humans to interpret the data. XML instances generally have the file extension .XML. XML schema documents generally have the file extension .XSD.

To assist human interpretation of XML instances, there is a further language, XSLT (eXtensible Stylesheet Language Transformations). This can transform an XML instance document into an easily-understandable HTML page which can be viewed in a standard web browser. XSLT files usually have the extension .XSLT.