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


1.3 What DFDL is not

DFDL maps data from a non-XML representation to an instance of an information set. This can be thought of as a data transformation. However, DFDL is not intended to be a general transformation language and, in particular, DFDL does not intend to provide a mechanism to map data to arbitrary XML models. There are two specific limitations on the data models that DFDL can work to:

  1. DFDL uses a subset of XML Schema, in particular, you cannot use XML attributes in the data model.

  2. The order of the data in the data model must correspond to the order and structure of the data being described.

This latter point deserves some elaboration. The XML schema used must be suitable for describing the physical data format. There must be a correspondence between the XML schema's constructs and the physical data structures. For example, generally the elements in the XML schema must match the order of the physical data. DFDL does allow for certain physically unordered formats as well.

The key concept here is that when using DFDL, you do not get to design an XML schema to your preference and then populate it from data. That would involve describing the data format, and describing a transformation for mapping it to the XML schema you have designed. DFDL is only about the format part of this problem. There are other languages, such as XSLT, which are for transformation. In DFDL, you describe only the format of the data, and this format constrains the nature of the XML schema you must use in its description.


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