SPDL Structure

The SPDL structure is the result of the division and repeated subdivision of an SPDL instance into increasingly smaller parts. This process results in a hierarchical structure.

The notation employed to specify the SPDL structure is declarative in nature, as opposed to the content notation, which takes the form of a procedural language. The structure also implies a sequential order for the set of structure elements which comprise the document.

Hierarchical structure

The following concepts and terminology are associated with the hierarchical structure and the relationships implied by that structure.

Structure elements

The elements of an SPDL document which are distinguished by the document structure are called structure elements.

Composite structure elements

A structure element which is subdivided into smaller structure elements is called a composite structure element. For each composite structure element, the defining clause specifies which subordinate structure elements may occur.

Base structure elements

A structure element which cannot be subdivided into smaller structure elements is called a base structure element.

Every base structure element has a value. The value of a base structure element belongs to one of the types defined in . For each base structure element, the defining clause specifies the type of the value of the structure element.

Subordinates and immediate subordinates

The parts into which a composite structure element has been subdivided are said to be the immediate subordinates of the composite structure element.

Since the immediate subordinates of a composite structure element may be composite structure elements, there may be structure elements which are the result of the further subdivision of a composite structure element which are not themselves immediate subordinates of that structure element. All of the structure elements, composite or base, which result from the further subdivision of a structure element are said to be subordinates of or subordinate to that structure element.

Reference to the immediate subordinates of a structure element always uses the form "immediate subordinates" or "immediately subordinate". When the term "subordinate" is used without this qualifier it means subordinate to any hierarchical level.

Superiors and immediate superiors

It is often necessary to refer to the structure element or structure elements to which a particular structure element is subordinate. A structure element A is said to be superior to a structure element B (or a superior of B) if B is subordinate to A. A structure element A is said to be immediately superior to a structure element B if B is immediately subordinate to A.

Reference to the immediate superior of a structure element always uses the form "immediate superior" or "immediately superior". When the term "superior" is used without this qualifier it means a structure element which is superior to any hierarchical level.

Most immediately superior structure elements

In describing the structure or processing of a structure element A, the phrase the most immediately superior X, means the structure element B for which

Peers

Structure elements immediately subordinate to the same structure element are called peers. Structure elements which are neither subordinate nor superior to each other, and which do not share the same immediate superior, are unrelated.

Highest structure level

A structure element which is not subordinate to any other structure element is said to be at the highest structure level.

Document Structure Elements

A structure element which is subordinate to a DOCUMENT is called a Document Structure Element. A structure element of class X which is a Document Structure Element is called a Document X.

Scope

The scope of a Document Structure Element is the part of the document which can be affected by it. The end of the scope of a Document Structure element is the end of the most immediately superior BLOCK. The scopes of two Document Structure Elements which affect the same aspect of document processing, such as two Document Production Instructions, may overlap. The effects of overlapping scope are implied by the structure processing specifications.

The scope of the binding of an Identifier to a resource or an external structure element is the part of the document in which the Identifier can be used to reference the resource or external structure element to which it is bound. The end of the scope of the binding of an Identifier to a resource or an external structure element by a structure element is the end of the most immediately superior BLOCK. The scopes of two such bindings may overlap. The effects of overlapping scope are implied by the structure processing specifications.

Sequential Order

In addition to a hierarchical structure, the SPDL structure assigns a sequential order to the immediate subordinates of each of the composite structure elements.

The combination of the hierarchical structure and the sequential order of peer structure elements generates a sequential order for the set of structure elements which comprise the SPDL INSTANCE. Structure elements that come later in this sequential order are said to follow the structure elements that come earlier, while the earlier structure elements are said to precede later structure elements.

Sequential Order and Hierarchical Structure

The sequential order is related to the hierarchical structure by two rules:

Thus the sequential order has the property of being "pre-order depth-first" relative to the hierarchical structure.

Example

An example of the relationship of the sequential order to the hierarchical structure is shown in . Relationship of Hierarchical Structure in Sequential Order In this example the structure elements are indicated by boxes, with subordinates being indicated by connecting lines. The order of the immediate subordinates of each structure element is left-to-right as indicated by the arrows. The sequential order for the structure elements is identified by the numbers in the boxes.

Presentation Order

This sequential order of structure elements is also the presentation order of an SPDL document. This order is the order in which the Structure Processor processes the structure elements in the presentation of the document.

The term presentation order may be used to refer to the sequential order of a subset of the structure elements within an SPDL document. For instance, the "presentation order of PAGE structure elements" within the SPDL document is the order in which PAGE structure elements occur within the sequential order of the SPDL document. The presentation order of PAGE structure elements is the order in which the pages of the document are presented to the user.

Ordinal Page Number

Each of the PAGE structure elements is assigned an ordinal page number which identifies the PAGE structure element for the purposes of document presentation. The ordinal page numbers are assigned in the presentation order of the PAGE structure elements within the document.

Pages and Imposition

An imposition process may place two or more "logical pages" on a single sheet. Such an imposition process is part of the Composition and Layout Process. In the resulting SPDL document, each PAGE structure element describes the image to be placed on an entire sheet, which may include several "logical pages". The SPDL Presentation Process has no knowledge of the component logical pages, but only of the PAGE structure elements and the associated page images. The ordinal page numbers used in document presentation refer to the PAGE structure elements, and have no relationship to any page numbers which may be associated with the "logical pages" of the document.

Identification of Information Objects

Information objects in the environment of the Presentation Process which are used in the presentation of documents are identified by

Some of these information objects are defined by this International Standard, whereas others are defined elsewhere.

Public Object Identifiers

ASN.1 object identifiers and public identifiers defined by ISO/IEC 9070 are referred to as Public Object Identifiers.

  • Public Object Identifiers provide unambiguous identification of information objects in open interchange, even in situations in which the information object identified may not be known.
  • An information object that is used in an ASN.1 environment will generally be assigned an ASN.1 object identifier value.
  • An information object that is used in an SGML environment will generally be assigned an ISO/IEC 9070 public identifier value.
  • There is, in general, no conversion or mapping that can be used to convert an ASN.1 object identifier value into an ISO/IEC 9070 public identifier which identifies the same information object. Similarly, there is no way to convert an ISO/IEC 9070 public identifier into an ASN.1 object identifier value which identifies the same information object.
  • To allow both structure representation and interchange formats to carry both kinds of Public Object Identifier, the Binary Structure Representation and Interchange Format defines a representation for ISO/IEC 9070 public identifiers, and the Clear Text Structure Representation and Interchange Format defines a representation for ASN.1 object identifiers. These representations apply only to this International Standard.
  • Assignment of Public Object Identifiers

    This International Standard defines Public Object Identifiers for the identification of several information objects. For each such information object, this International Standard specifies both

    which identify that information object.

    Each information object for which this International Standard defines a Public Object Identifier is identified by an Object Name. This Object Name is the "object name" part of the ISO/IEC 9070 public identifier which is assigned to it. The full ISO/IEC 9070 public identifier and the ASN.1 object identifier value which identify the information object are specified in .

    The identification of an information object which is defined by this International Standard in an instance of SPDL Structure should use:

    Notation

    The text of this International Standard describes the effect of several parameter values which are specified by means of a Public Object Identifiers. In these cases, the parameter value represented by the Public Object Identifier is represented by the Object Name corresponding to that Public Object Identifier in italics, e.g. dpi:plex:simplex.

    Environment Names

    An information object in the environment of the Presentation Process may also be identified by an Environment Name. An Environment Name consists of single object-name component as defined by ISO/IEC 9070.

    An Environment Name is semantically equivalent to the ISO/IEC 9070 public identifier for which the owner name is the word "UNREGISTERED" and the object name consists of a single object-name component. Specifically, the Environment Name "objectname" is semantically equivalent to the public identifier for which

    Environment Names are meaningful only within a particular domain of use. This domain may consist of a single system, a set of related systems, or a broader domain in which a set of naming agreements has reached. Environment Names may be ambiguous if used in open interchange.

    Representation and Interchange Format

    The SPDL structure is easily parsable by a variety of processes. These include imposition processes and processes which extract pages or pictures from SPDL documents as well as Presentation Processes. To support the parsing of the SPDL structure by a variety of processes in a variety of environments, both ASN.1 and SGML encodings of the SPDL structure are standardized. An SPDL Presentation Process only needs to be able to process one of the representations to conform to this International Standard.

    The SPDL structure enables processes to extract elements from SPDL documents together with relevant attributes, and to determine external resource requirements, without having to interpret the content elements which specify page and picture images. No process other than an SPDL Presentation Process needs to be able to process the content notation.

    The SPDL structure specifies the logical structure of an instance of SPDL. Not every structure element need have an explicit representation in the Structure Representation and Interchange Format, so long as the logical structure of each instance of SPDL is unambiguously represented.

    This International Standard specifies two representation and interchange formats for the encoding of the SPDL structure:

    The Binary Structure Representation and Interchange Format is based on ASN.1. The Clear Text Structure Representation and Interchange Format is based on SGML. The Binary Structure Representation and Interchange Format and the Clear Text Structure Representation and Interchange Format are fully equivalent: any functionality that can be expressed in one can be expressed in the other with a simple syntactic transformation.

    The Structure Representation and Interchange Formats ensure that every instance of SPDL is self-identifying within the domain of use of the structure notations on which the Structure Representation and Interchange Formats are based.

    This International Standard also specifies two Representation and Interchange Formats for the encoding of the token sequences which comprise the content:

    For reasons of compactness and efficiency of interpretation, specialized representations optimized for compactness and ease of interpretation are used.

    The Binary Content Representation and Interchange Format is used with the Binary Structure Representation and Interchange Format. The Clear Text Content Representation and Interchange Format is used with the Clear Text Structure Representation and Interchange Format.

    Instances of the Standard Page Description Language

    An instance of the Standard Page Description Language may represent a document, define or undefine a resource, or encapsulate a structure element which may be included in another instance of SPDL by reference.

    An SPDL Instance consists of an SPDL Identifier and a TOP LEVEL STRUCTURE structure element. The SPDL Identifier identifies an SPDL Instance unambiguously as such among data structures which are encoded using the structure notation used by the Structure

    Representation and Interchange Format (ASN.1 or SGML). The TOP LEVEL STRUCTURE structure element is the structure element at the highest structure level of the SPDL Instance.

    Binary Structure Representation and Interchange Format

    An SPDL Instance in the Binary Structure Representation and Interchange Format shall be encoded as an instance of the ASN.1 EXTERNAL type for which

    Clear Text Structure Representation and Interchange Format

    An SPDL Instance in the Clear Text Structure Representation and Interchange Format shall be encoded as an SGML document instance for which

    TOP LEVEL STRUCTURE

    A TOP LEVEL STRUCTURE structure element shall be one of:

    which is not subordinate to any other structure element.

    Comments

    The Structure Representation and interchange Format allows for the the inclusion of comments in any instance of SPDL. The method of including comments in an instance of SPDL Instance depends on the Structure Representation and Interchange Format being used. Comments shall have no effect on either structure processing or content processing.

    Comments consist of IA5Strings (as defined in ISO/IEC 8824) which do not interfere with the parsing of the chosen Structure Representation and Interchange Format. The set of comments which may occur depends on the Structure Representation and Interchange Format being used. This has no effect on the presentation of an SPDL document since comments are ignored by the Structure Processor.