Data Format Description Language (DFDL) v1.0 Specification
OGF Proposed Recommendation GFD-P-R.174, January 31, 2011


5. DFDL Schema Component Model

When using DFDL, the format of data is described by means of a DFDL Schema. The DFDL Schema Component Model is shown in conceptual UML in Figure 2. First we show the model for elements, groups and the top of the type hierarchy.

The shaded boxes have direct corresponding element syntax and therefore appear in DFDL schema.

Diagram representing the DFDL Schema in UML form
Figure 2. DFDL Schema UML diagram

The simple types are shown in Figure 3. The graph shows all the types defined by XML Schema version 1.0, and the subset of these types supported by DFDL are shown as shaded.

Tree diagram of the DFDL simple types
Figure 3. DFDL simple types

These types are defined as they are in XML Schema, with exceptions for:
  • String – In DFDL a string can contain any character codes. None are reserved. (Including the character with character code U+0000, which is not permitted in XML documents.)

Each object defined by a class in the above UML is called a DFDL Schema component. We express the DFDL Schema Model using a subset of the XML Schema Description Language (XSDL). XSDL provides a standardized schema language suitable for expressing the DFDL Schema Model.

A DFDL Schema is an XML schema containing only a restricted subset of the constructs available in full W3C XML Schema Description Language. Within this XML schema, special DFDL annotations are distributed that carry the information about the data format or representation.

A DFDL Schema is a valid XML schema. However, the converse is not true since the DFDL Schema Model does not include many concepts that appear in XML schema.


Copyright (C) Open Grid Forum (2005-2010). All Rights Reserved.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the OGF or other organizations, except as needed for the purpose of developing Grid Recommendations in which case the procedures for copyrights defined in the OGF Document process must be followed, or as required to translate it into languages other than English.