This clause describes the general architecture of the
Standard Page Description Language.
The basic document processing model consists of three
processes and two forms of document representation as
illustrated in The The Creation and Editing Process is responsible for the
creation of the character text and graphics which comprise the
logical content of the document and for the logical structure of
the document. It may also generate information which specifies
how the Composition and Layout Process is to format the document
for presentation.
The revisable form document represents the logical content
and structure of the document created by the Editing Process. It
also includes any information generated by the Editing Process
which specifies how the document is to be formatted for
presentation.
The Composition and Layout Process composes character text of
the document, formats any graphical elements, and lays out the
composed character text and graphics for presentation. All
composition, formatting, and positioning decisions are made by
the Composition and Layout Process. These decisions include such
details as
The formatting specifications which direct the Composition
and Layout Process may be part of the revisable form document or
they may be separate from the document. ISO/IEC 10179
defines one form for formatting specifications which are not
part of the revisable form document.
In addition to the revisable form document and formatting
specifications, input to the Composition and Layout Process may
include previously formatted elements which are to be
incorporated in the final form document.
The final form document represents the results of the
composition, formatting, and positioning decisions made by the
Composition and Layout Process. It is not required to represent
the logical document structure, the formatting specifications,
or the intent of those decisions.
The Presentation Process presents an document by rendering it
in visible form on suitable media. It also performs any
finishing operations (e.g. trimming, stapling, or binding) which
are part of document presentation.
SPDL is a final form document format. As such it provides
facilities for the efficient representation of the decisions
made by the Composition and Layout Process. SPDL does not
provide facilities for the representation of logical document
structure.
The primary source of SPDL documents is the application of a
Composition and Layout Process to a revisable form document. In
addition, an SPDL document may also be created by:
The SPDL document represents the ideal image specified by the
Composition and Layout Process. It is the responsibility of
the SPDL Presentation Process to adapt the rendering of the
document to the constraints of the presentation device so as to
provide the best possible approximation to the description
specified by the Composition and Layout Process.
An SPDL document may be presented many times, at different
times and/or places. For this reason document presentation must
accommodate parameters which may be specific to a particular
instance of presentation. These parameters are specified by
Document Production Instructions may be conveyed to the
Presentation Process as part of the SPDL document or made
available via a separate mechanism. The method by which Document
Production Instructions which are not a part of the document are
made available to the Presentation Process is outside the scope
of this International Standard.
The primary use of SPDL documents is input to an SPDL
Presentation Process. In addition, an SPDL document may be used
to represent a formatted portion of document content. Such
previously formatted document content may be used as input to a
Composition and Layout Process for inclusion in another
document.
An SPDL document has The content is in the form of a page description language
which specifies how the page images are to be generated. The
processing of the content is dependent on the processing of the
structure: the processing of the structure establishes the
context in which the content can be processed.
The Presentation Process may also have available to it
various sources of additional data, such as fonts or stored
portions of SPDL documents, which may be referenced by an SPDL
document. The sum of all such data is called the
The document structure is the result of the division and
repeated subdivision of a document into increasingly smaller
parts. The resulting parts are called The document structure is hierarchical. The highest level
structure element is a DOCUMENT.
A DOCUMENT may contain subordinate PAGESET
and/or PAGE structure elements.
A PAGESET may in turn contain
subordinate PAGESET and/or PAGE structure
elements. Each PAGE contains the description of that
portion of the document which is to be presented on a single
instance of the presentation medium.
A PAGE may contain subordinate PICTURE
and/or TOKENSEQUENCE structure elements.
A PICTURE may contain subordinate PICTURE
and/or TOKENSEQUENCE structure elements.
A TOKENSEQUENCE is a structure element which contains
document content.
DOCUMENT and PAGE structure elements
are semantically distinct but are not syntactically
distinguished. A DOCUMENT is simply
a PAGESET or a PICTURE which is at the
highest level in the structure hierarchy. Similarly,
a PAGE is simply a PICTURE which is at the
highest level in the PICTURE hierarchy.
In addition to representing the division of an document into
smaller parts, the document structure supports:
The An A Since the SPDL document consists of document structure and
document content, and since these categories of data are
separable, the Presentation Process can be modeled as containing
subsidiary processes which process structure and content
separately. In this International Standard, these processes are
referred to as the Document structure processing consists of analyzing the
structure elements of the SPDL document, their types, their
hierarchical relationships, and the presentation order. For
presentation, structure processing also:
Document content processing consists of interpreting each
content element as a sequence of tokens in the Content
Representation and Interchange Format and processing those
tokens as specified in Document presentation includes all of the artifacts of the
Presentation Process, including the generation of error messages
and warnings.
SPDL documents are interchanged in the Representation and
Interchange Format defined in The binary form of the Structure Representation and
Interchange Format uses Abstract Syntax Notation 1
(ASN.1) as defined in ISO/IEC 8824 encoded
using the Basic Encoding Rules specified
by ISO/IEC 8825. The clear text form of the Structure
Representation and Interchange Format uses Standard Generalized
Markup Language (SGML) as defined
in ISO 8879 encoded
using ISO/IEC 646 IRV.
The Content Representation and Interchange Format uses
specialized encodings optimized for compactness and efficiency
for each of the binary and the clear text forms.
A Print Service which has the capability of printing SPDL
documents has an SPDL Presentation Process as part of the Print
Service. This clause discusses the relationship of such a Print
Service to the embedded SPDL Presentation Process.
When an SPDL document is printed by a Print Service, the
print operation parameters may include parameters which affect
document imaging and presentation. Such parameters specify
Document Production Instructions which are called
Supplementary DPI. The Print Service implementation
is responsible for making the SPDL document and
Supplementary DPI available to the SPDL Presentation
Process.
The SPDL Presentation Process resolves interactions between
Document Production Instructions which are provided as
Supplementary DPI associated with a particular
instance of presentation and any Document Production
Instructions contained in the SPDL document. This relationship
is illustrated in ISO/IEC 10175 defines a standard Document Printing
Application which provides a standard (abstract) Print Service.
Document printing is accomplished by the invocation of a Print
Operation accompanied by a document and a set of Print Operation
Parameters.
The Print Operation Parameters defined
by ISO/IEC 10175 consist of Print Job Management
Instructions and Document Production Instructions.
Print Job Management Instructions do not affect the
presentation of SPDL documents. Some, but not all, of the
Document Production Instructions defined
by ISO/IEC 10175 are applicable to an SPDL
Presentation Process.
The semantics of ISO/IEC 10175 Print Job
Management Instructions and the general semantics of those
Document Production Instructions which may occur
as ISO/IEC 10175 Print Operation Parameters are
defined by ISO/IEC 10175. The specific semantics of
those Document Production Instructions which may occur
as ISO/IEC 10175 Print Operation Parameters and which
are applicable to the presentation of SPDL documents, when used
in the presentation of SPDL documents, are defined by this
International Standard.
Creation and Editing Process
Revisable Form Document
Composition and Layout Process
Final Form Document
Presentation Process
SPDL Document
Sources of SPDL Documents
SPDL Document Presentation
Uses of SPDL Documents
SPDL Document Architecture
Document Structure
Document Content
External structure elements
Resources
Document Presentation
Representation and Interchange Format
Relationship to Print Services
Document Production Instructions
Relationship to ISO/IEC 10175