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


4.1 Information Items

An information set contains two different types of information items, as explained in the following sections. Every information item has members. For ease of reference, each member is given a name, indicated [thus].

4.1.1 Document Information Item

There is exactly one document information item in the information set, and all other information items are accessible through the [root] member of the document information item.

There is no specific DFDL schema component that corresponds to this item. It is a concrete artifact describing the information set.

The document information item has the following members:

  1. [root] The element information item corresponding to the root element declaration of the DFDL Schema.

  2. [dfdlVersion] String. The version of the DFDL specification to which this information set conforms. For DFDL V1.0 this is 'dfdl-1.0'

  3. [schema] String. A reference to a DFDL schema associated with this information set, if any. If not empty, the value must be an absolute Schema Component Designator [http://www.w3.org/TR/xmlschema-ref].

4.1.2 Element Information Items

There is an element information item for each value parsed from the non-hidden DFDL-described data. This corresponds to an instance of a non-hidden element declaration of simple type in the DFDL Schema and is known as a simple element information item.

There is an element information item for each explicitly declared structure in the DFDL-described data. This corresponds to an instance of an element declaration of complex type in the DFDL Schema and is known as a complex element information item.

In this information set, as in an XML document, an array is just a set of adjacent elements with the same name and namespace. (To represent the array explicitly, introduce a new complex type element to contain the array elements only.)

One of the element information items is the [root] member of the document information item, corresponding to the root element declaration of a DFDL Schema, and all other element information items are accessible by recursively following its [children] member.

An element information item has the following members:

  1. [namespace] String. The namespace, if any, of the element. If the element does not belong to a namespace, the value is the empty string.

  2. [name] String. The local part of the element name.

  3. [document] The document information item representing the DFDL information set that contains this element. This element is empty except in the root element of an information set.

  4. [datatype] String. The name of the XML Schema 1.0 built-in simple type to which the value corresponds. DFDL supports a subset of these types listed in section ‎5.1 DFDL Subset of XML Schema. In a complex element information item this member has no value.

  5. [dataValue] The value in the value space (as defined by XML Schema Part 2: Datatypes [XSDLV1] ) of the [datatype] member or special value nil. In a complex element information item this member has no value. For information items of datatype xs:string, the value is the ISO 10646 character codes of the string and 'implicit' (also known as logical), left-to-right bidirectional ordering and orientation. During parsing, characters whose value is unknown or unrepresentable in ISO 10646 are replaced by the Unicode Replacement Character U+FFFD. During unparsing, characters that are unrepresentable in the target encoding will be replaced by the replacement character for that encoding.

  6. [children] An ordered set of zero or more element information items. The order they appear in the set is the order implied by the DFDL Schema. ‘Ordered set’ is not formally defined here, but two operations are assumed: ‘count’ gives the number of information items, and ‘at (index)’ gives the element at ordinal position ‘index’ starting from 1. In a simple element information item this member has no value. In a document information item this member contains exactly one element information item.

  7. [parent] The complex element information item which contains this information item in its [children] member. In the root element of an information set this member is empty.

  8. [schema] String. A reference to a schema component associated with this information item, if any. If not empty, the value must be an absolute or relative Schema Component Designator.


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