XSD-Driven XML Reader/Writer

Licensing options for this format begin with FME Desktop Professional Edition.

The XSD-Driven XML modules allows FME to read and write XML documents based on the schema from XML Schema (W3C XSD) documents.

This chapter assumes familiarity with XML and XML Schemas.


This Reader/Writer allows FME to read and write any XML document that conforms to the application schema provided. XML documents must be instances of a conforming application schema. Application schemas are to be defined with the W3C’s XML Schema language.

XML and XML Schemas (W3C XSDs) are recommendations of the World Wide Web Consortium (W3C). More information on XML and W3C XSDs can be found in the W3C website.

The XSD-Driven XML reader/writer provides two mechanisms to map elements declared in the XSD Schemas into features:

1. By specifying a list of top-level element declarations from the XSD Schemas, via the “Feature Paths” parameter.
2. By specifying a list of complex type definitions that are used as the type in the XSD Schemas’ element declarations.

Reader Overview

The XSD-Driven XML reader maps XML elements into FME features.

These XML elements must correspond to top level element declarations, or reachable via top-level element declarations, in the XSD Schemas. The top-level element declarations from the XSD Schemas can be identified with the reader’s Feature Paths parameter.

Multi-value properties (that is, declared with a maxOccurs that is greater than 1 or unbounded) are supported and are mapped into list attributes. Null values are not read unless they are nillable. XML elements that are defined as complex types are supported – these nested elements are mapped as structured list attributes.

Writer Overview

The XSD-Driven XML writer writes XML documents conforming to an existing (W3C XSD) XML Schema document.

The FME feature types must correspond to top-level element declarations, or elements reachable via top-level element declarations, in the XSD Schemas. The top-level element declarations from the XSD Schemas can be identified with the writer’s Feature Paths parameter.

The writer writes a single XML document. If multiple features are routed into the writer, they must be composable into a single rooted tree via the xml_id and xml_parent_id attributes. Each feature (if it is to be composed into a single rooted tree) must have a unique xml_id. Each feature (if it is not the root) must have also have an xml_parent_id pointing back to its parent xml_id attribute value.

The writer’s XML Appender parameters may be used to help compose the final document. If the XML Document parameter is non-empty, then the specified document will be written as the output. Each rooted feature (features with no xml_parent_id), that is sent to the writer will be inserted into the XML Document. By default, the features that are mapped into XML according to the XSD are inserted right before the end tag of XML Document's root element. The append path and the manner of insertion can be controlled by the XML Document Append Path and XML Document Append As parameters. In addition, each of the rooted features may be further wrapped. This is useful if the features need to be wrapped in an element in the XML Document, say, <os:member>. See the XML Wrapper, XML Wrapper Append Path, and XML Wrapper Append As parameters.