XML Schemas describe the structure of an XML document. XML Schemas can be more powerful than any form of DTD (DocType Definition), and because of this, the web is evolving towards using XML Schemas more often than their DTD predecessors. XML Schemas also offer the support of namespaces, defining data types and are more extensible to further additions.

XML Schema Language is also referred to by the name XML Schema Definition, or XSD for short. Like DTD's, XSD's are the legal base of the document that they are governing. In short, they can define elements, child elements and values, and set whether each of these is to be displayed or not.

XDS's support for data types means that it is easier to describe and define numerous factors regarding the schema, or the data that will be governed by it. Schemas outline what content is allowed in the content, and whether the content is valid. It also simplifies the use of data from databases, as it defines a common structure that can be used across platforms. As a result of this, it is also easy to convert the data stored between data types.

When sending data between two computers, or two pieces of software, it's important that both applications have the same expectations of the data. By storing and transmitting in a structural format, with a readily available doctype to describe it, it will ensure that the transfer is not problematic to the end user.

XML also has predefined data types, such as date, which is shown as 2010-01-10. In some regions, the date string 10-01-2010 could be interpreted as January 10th, and in others it could be interpreted as October 1st. With the XML date definition above, confusion is eliminated, as the date type required the format of YYYY-MM-DD.

Various other advantage of XML is that it uses language to describe elements, making it more understandable for humans to read. This means that collaborating on documents can be easier, and new and younger developers can get on board, as this makes it very easy to understand. As well as this, it can be used on any platform that is capable of running Java, meaning it is a cross platform language, including smart phones, and proprietary systems.

Over the past 10 years, methods of creating, writing and editing XML have evolved. Due to the structural nature of the language, graphical representations of schemas and files are possible. This has lead to an increase in the use of GUI's in the development stage.