An
An SPDL Instance that includes an External Structure Element by reference must declare it in an EXTERNAL DECLARATION. The EXTERNAL DECLARATION identifies a data element in the environment of the Presentation Process and binds an Identifier to the External Structure Element contained in that data element. The way in which the External Structure Element is obtained from the referenced data element depends on the referenced data element.
An External Structure Element which is declared in an EXTERNAL DECLARATION may be included by reference in an SPDL Instance by placing an EXTERNAL REFERENCE in the SPDL Instance. The EXTERNAL REFERENCE can be placed at any position in the structure of SPDL Instance the within the scope of the binding of the Identifier to the External Structure Element where the External Structure Element could occur. The Structure Processor processes the EXTERNAL REFERENCE structure element by substituting the referenced External Structure Element for the EXTERNAL REFERENCE structure element.
The definitions of structure elements and their subordinates within this International Standard take no further note of the fact that an EXTERNAL REFERENCE may be substituted for any of the structure elements specified.
An INCLUDABLE STRUCTURE structure element is a structure element which is defined by this International Standard and which can be included in another SPDL Instance by the use of an EXTERNAL REFERENCE structure element. An INCLUDABLE STRUCTURE structure element shall be one of:
An EXTERNAL DECLARATION structure element binds an Identifier to an External Structure Element. An EXTERNAL DECLARATION structure element shall be a composite structure element which shall have the following immediate subordinates:
The immediate subordinates shall occur in the above order.
A STRUCTURE ELEMENT CLASS IDENTIFIER structure
element shall be a base structure element. The type of the value
of a STRUCTURE ELEMENT CLASS IDENTIFIER shall be an
Enumerated type which identifies the structure element
referenced by an EXTERNAL DECLARATION as an element
of the specified class. The values of this type and the class of
structure elements identified shall be as shown in A STRUCTURE ELEMENT IDENTIFIER structure element
shall be a base structure element. The value of
a STRUCTURE ELEMENT IDENTIFIER shall be of type Processing an EXTERNAL DECLARATION structure
element shall consist of binding the value of
the STRUCTURE ELEMENT IDENTIFIER to an External
Structure Element. The scope of the binding shall be the set of
all structure elements in the most immediately
superior BLOCK which follow
the EXTERNAL DECLARATION in the sequential order and
all of their subordinates. The effect of the binding can be
overridden by a subsequent EXTERNAL DECLARATION of
the same kind in the same BLOCK or in a
subordinate BLOCK.
If an EXTERNAL DECLARATION falls within the scope
of a preceding EXTERNAL DECLARATION for which the
value of the STRUCTURE ELEMENT IDENTIFIER is the
same, the binding specified by the
later EXTERNAL DECLARATION shall take precedence
within its own scope.
The occurrence of an EXTERNAL DECLARATION for
which either
does not result in a structure error or warning.
A LOCATION IDENTIFIER structure element identifies
a data element which is either
When used to identify an External Structure Element, the data
element identified by the LOCATION IDENTIFIER may be
the External Structure Element itself, or it may be a data
element containing the External Structure Element or a process
which can be used to obtain the External Structure Element. The
relationship between the identified data element and the
referenced External Structure Element is
specified in Since the methods by which information objects are identified
differ between environments in which the encoding method used is
predominantly ASN.1 and those in which the encoding
method used is predominantly SGML, the structure of
the LOCATION IDENTIFIER depends on the structure
representation used. A LOCATION IDENTIFIER structure
element shall be one of:
A PUBLIC LOCATION IDENTIFIER structure element
shall be a base structure element. The value of
a PUBLIC LOCATION IDENTIFIER shall be of type The way in which the Public Object Identifier which is the
value of the PUBLIC LOCATION IDENTIFIER identifies a
data element in the environment of the Presentation Process is
outside of the scope of this International Standard.
A LOCAL LOCATION IDENTIFIER structure element
shall be a base structure element. The value of
a LOCAL LOCATION IDENTIFIER shall be of type This value of a LOCAL LOCATION IDENTIFIER
structure element identifies a data element in the local syntax.
The way in which this value identifies a data element is outside
of the scope of this International Standard.
The ENCODING DEPENDENT LOCATION IDENTIFIER
structure element depends on the structure representation used.
When the Binary Structure Representation and Interchange
Format is used,
an ENCODING DEPENDENT LOCATION IDENTIFIER shall be
one of:
When the Clear Text Structure Representation and Interchange
Format is used,
an ENCODING DEPENDENT LOCATION IDENTIFIER shall be
one of:
The way in which
the ENCODING DEPENDENT LOCATION IDENTIFIER identifies
a data element in the environment of the Presentation Process is
outside of the scope of this International Standard.
A DOR LOCATION IDENTIFIER structure element shall
be a Distinguished Object Reference (DOR) as defined
by ISO/IEC 10031-2.
An IDENTIFIED SYNTAX LOCATION IDENTIFIER structure
element shall be an instance of the ASN.1 EXTERNAL
type which shall have the following components:
An SGML SYSTEM IDENTIFIER shall be
an SGML external identifier as defined
by ISO 8879.
An SGML ENTITY shall be an SGML general
entity name as defined by ISO 8879.
The value of the LOCATION IDENTIFIER may identify
the External Structure Element directly, or it may identify a
data element containing the External Structure Element or a
process which can be used to obtain the External Structure
Element. The identification of the External Structure Element
which is identified by an EXTERNAL DECLARATION can be
considered as a two step process:
If the value of the LOCATION IDENTIFIER identifies
the External Structure Element directly, the data element
identified in the first step is simply the External Structure
Element itself
The data element which is identified by
the LOCATION IDENTIFIER may be:
The External Structure Element referenced in each of these
cases shall be:
An EXTERNAL REFERENCE structure element shall be a
base structure element. The value of
an EXTERNAL REFERENCE shall be of type Processing an EXTERNAL REFERENCE structure element
shall consist of:
If any of the above steps fails the Structure Processor shall
raise an error.
STRUCTURE ELEMENT IDENTIFIER
EXTERNAL DECLARATION Processing
LOCATION IDENTIFIER
PUBLIC LOCATION IDENTIFIER
LOCAL LOCATION IDENTIFIER
ENCODING DEPENDENT LOCATION IDENTIFIER
DOR LOCATION IDENTIFIER
IDENTIFIED SYNTAX LOCATION IDENTIFIER
SGML SYSTEM IDENTIFIER
SGML ENTITY
Referenced Structure Element Identification
EXTERNAL REFERENCE
EXTERNAL REFERENCE Processing