In order to use the XML Data Access Service for Service Data Objects, you will need to understand some of the concepts behind SDO: the data graph, the data object, XPath and property expressions, and so on. If you are not familiar with these ideas, you might want to look first at the section on SDO.
The job of the XML DAS is to move data between the application and an XML data source, which can be either a file or a URL. SDOs are always created and maintained according to a model which defines type names and what property names each type may have. For data which is from XML, this SDO model is built from a schema file written in XML schema language (an xsd file). This schema file is usually passed to the create method when the XMLDAS is initialised. The » SDO 2.0 specification defines the mapping between XML types and SDO types. There are a number of small limitations in the PHP support - not everything which is in the specification can be done - and these limitations are summarised in a later section.