The previous XSD definitions are shown graphically in Liquid XML Studio as follows: (Failure to do this will cause a validation error.) Examples of simple elements and their XML are below: Sample XSD If you have set the type property for an element in the XSD, the corresponding value in the XML document must be in the correct format for its given type. You also can create a user-defined type by using the and tags, but more on these later. There are a number of predefined types, such as xs:string, xs:integer, xs:boolean or xs:date (see the XSD standard for a complete list). The type property provides the description of what can be contained within the element when it appears in the XML document. An element can be defined within an XML Schema (XSD) as follows: Īn element definition within the XSD must have a name property this is the name that will appear in the XML document. ElementsĮlements are the main building block of any XML document they contain the data and determine the structure of the document. The remainder of this tutorial guides you through the basics of the XSD standard, things you should really know even if you’re using a design tool like Liquid XML Studio.
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For this reason, it is a good idea to make use of design tools when working with XSDs ( See XML Studio, a FREE XSD development tool), also when working with XML documents programmatically XML Data Binding is a much easier way to manipulate your documents (a object-oriented approach see Liquid XML Data Binding). It is extremely comprehensive, and as a result has become rather complex. The XSD standard has evolved over a number of years, and is controlled by the W3C. There are also a number of other standards, but their take up has been patchy at best. ( You have to dig quite deep before you notice the difference.) An XSD schema is itself an XML document there is even an a XSD schema to describe the XSD standard. There are two versions in use, 1.0 and 1.1, which are on the whole the same. XSD is currently the de facto standard for describing XML documents. This standard has pretty much been abandoned now in favor of XSD. XDR was an early attempt by Microsoft to provide a more comprehensive standard than DTD. A Note About StandardsĭTD was the first formalized standard, but is rarely used anymore. It also can describe the values that can be placed into any element or attribute.
An XML schema describes the coarse shape of the XML document, what fields an element can contain, which sub elements it can contain, and so forth. A schema formally describes what a given XML document contains, in the same way a database schema describes the data that can be contained in a database (table structure, data types). It covers:įirst, look at what an XML schema is.
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This article gives a basic overview of the building blocks underlying XML Schemas and how to use them. XSD Tutorial, Part 1 of 5: Elements and Attributes
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