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Description  |
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BACKGROUND OF THE INVENTION
1. Documents Incorporated by Reference
This invention discloses a method and system for management of logical
links between document elements during document interchange within the
Mixed Object Document Content Architecture (MO:DCA) used within a
presentation data stream for document interchange. Background material for
an understanding of this invention is incorporated by reference from Mixed
Object Document Content Architecture Reference, IBM Publication
SC31-6802-03, 1994 and will be referred to herein as Mixed Object Document
Content Architecture (MO:DCA).
2. Background of the Invention
The present invention relates in general to an improved method and system
for presentation data stream management and in particular to an improved
method and system for presentation data stream management which supports
logical links between various document components within the data stream.
Still more particularly, the present invention relates to an improved
method and system for presentation data stream management which supports
logical links between various document components within the data stream
and which explicitly identifies the purpose of each link so that the link
may be selectively processed or ignored by a receiver.
3. Description of the Related Art
Presentation architectures are provided for representing documents in a
data format which is independent of the methods utilized to capture or
create those documents. Documents may contain combinations of text, image,
graphics, and/or bar code objects in device and resolution independent
formats. Documents may also contain fonts, overlays and other resource
objects which are required at presentation time to present the data
properly. Additionally, documents may also contain resource objects, such
as a document index and tagging elements supporting the search and
navigation of document data, for a variety of application purposes.
A data stream is a continuous ordered stream of data elements and objects
which conform to a given format. Application programs can generate data
streams destined for a presentation service, archive library or another
application program. The Mixed Object Document Content Architecture
(MO:DCA) developed by International Business Machines Corporation of
Armonk, N.Y. defines a data stream which may be utilized by applications
to describe documents and object envelopes for interchange with other
applications and application services. Documents which are defined in the
Mixed Object Document Content Architecture (MO:DCA) format may be archived
in a database, later retrieved, viewed, annotated and printed in local or
distributed system environments. Presentation fidelity is accommodated by
including resource objects in the documents that reference those objects.
A mixed object document is a collection of data objects which comprise the
document's content and the resources and formatting specifications which
dictate the processing functions to be performed on that content. The term
"Mixed" in the Mixed Object Document Content Architecture (MO:DCA) refers
to both the mixture of data objects and the mixture of document constructs
that comprise the document's components. A Mixed Object Document Content
Architecture (MO:DCA) can contain a mixture of presentation data objects.
Each data object type has a unique processing requirement.
The Mixed Object Document Content Architecture (MO:DCA) is designed to
facilitate document interchange as well as document exchange, Interchange
is the predictable interpretation of shared information in an environment
where the characteristics of each process need not be known to all other
processes. Exchange is the predictable interpretation of shared
information by a family of system processes in an environment where the
characteristics of each process must be known to all other processes.
The Mixed Object Document Content Architecture (MO:DCA) is designed to
integrate the different data object types into documents that can be
interchanged as a single data stream. The Mixed Object Document Content
Architecture (MO:DCA) provides the data stream structures need to carry
the data objects. The data stream also provides syntactic and semantic
rules governing the use of those objects to ensure that different
applications process those objects in a consistent manner.
In its most complex form, a Mixed Object Document Content Architecture
(MO:DCA) contains data objects along with data structures which define the
document's layout and composition features. This form is called a Mixed
Object Document Content Architecture (MO:DCA) presentation document.
Within such a data stream the Mixed Object Document Content Architecture
(MO:DCA) components are defined with a syntax that consists of
self-describing structures. Structured fields are the main Mixed Object
Document Content Architecture (MO:DCA) structures and are utilized to
encode Mixed Object Document Content Architecture (MO:DCA) commands. A
structured field typically starts with an introducer that uniquely
identifies the command, provides a total length for the command, and
specifies additional control information such as whether padding bytes are
present. The introducer is then followed by up to 32,759 data bytes. Data
may be encoded within the structured field utilizing fixed parameters,
repeating groups, key words and triplets. Fixed parameters have a meaning
only in the context of the structure that includes them. Repeating groups
are utilized to specify grouping of parameters that can appear multiple
times. Key words are self-identifying parameters that consist of a one
byte unique key word identifier followed by a one byte keyword value.
Triplets are self-identifying parameters that contain a one byte length, a
one byte unique triplet identifier and up to 252 data bytes. Key words and
triplets have the same semantics whenever they are utilized. Together
these structures define a syntax for Mixed Object Document Content
Architecture (MO:DCA) data streams which provide for orderly parsing and
flexible extendibility.
The document is the highest level within the Mixed Object Document Content
Architecture (MO:DCA) data stream document component hierarchy. Documents
may be constructed of pages, and the pages, which are at the intermediate
level, may be made up of objects. Objects are at the lowest level and can
be bar codes, graphics, images and presentation text.
A Mixed Object Document Content Architecture (MO:DCA) document in its
presentation form is a document which has been formatted and is intended
for presentation, usually on a printer or a display device. A data stream
containing a presentation document should produce the same document
content in the same format on different printers or display devices
dependent, however, on the capabilities of each of the printers or display
devices. A presentation document can reference resources that are to be
included as part of the document to be presented which are not present
within the data stream.
Pages within the Mixed Object Document Content Architecture (MO:DCA) are
the level within the document component hierarchy which is utilized to
printing or displaying a document's content. Data objects contained within
each page envelope in the data stream are presented when the page is
presented. Each data object has layout information associated with it that
directs the placement and orientation of the data on the page. In
addition, each page contains layout information and specifies the
measurement units, page width and page depth.
Data objects within the Mixed Object Document Content Architecture (MO:DCA)
contain the data which is to be presented. Such objects may also contain
environment information needed to establish the proper location and
orientation for the data on the presentation surface. Objects in the data
stream are bounded by delimiters that identify the object type, such as
graphics, image or text. The Mixed Object Document Content Architecture
(MO:DCA) supports two categories of objects: data objects, and resource
objects. In general data objects consist of data to be presented and the
directives required to present it. The content of each type of data object
is defined by an object architecture that specifies presentation functions
which may be utilized within its coordinate space. All data objects
function as equals within the Mixed Object Document Content Architecture
(MO:DCA) data stream environment. Data objects are carried as separate
entities with no dependencies on the Mixed Object Document Content
Architecture (MO:DCA) layout structures or the containing data stream
environment. Resource objects are named objects or named collection of
objects that can be referenced from within the document. In general,
referenced resources can reside in a resource group that precedes the
document or in an external resource library and can be referenced over and
over.
An object container within the Mixed Object Document Content Architecture
(MO:DCA) is an envelope for object data that may not be defined by an
International Business Machines Corporation presentation architecture and
that may not define all required prosecution parameters. The container
consists of a mandatory Begin/End structured field pair, an optional
Object Environment Group (OEG) and optional Object Container Data (OCD)
structured fields. If an object is to be carried in Mixed Object Document
Content Architecture (MO:DCA) resource groups and interchanged, it must,
at a minimum, be enveloped by a Begin/End pair, and the Object
Classification triplet on the Begin structured field must specify the
registered object identifier (OLD) for the object data format.
The processing of final-form or presentation document data streams is
currently being extended from presentation on hard-copy devices such as
printers to presentation on viewers which include interactive functions
such as context-based navigation and annotation. When applied to a
final-form document presentation data stream, such as that defined by
Mixed Object Document Content Architecture (MO:DCA) document presentation
data stream, these new functions require a method of defining logical
links between the various document components. Further, it would be useful
to provide a definition for such logical links which identifies the
source, target and the purpose of the link such that receivers of the
document data stream can parse the identifying structure and dynamically
determine whether to process or ignore the link.
SUMMARY OF THE INVENTION
It is another object of the present invention to provide an improved method
and system for data stream management.
It is yet another object of the present invention to provide an improved
method and system for data stream management which supports logical links
between various document components within the data stream.
It is still another object of the present invention to provide an improved
method and system for data stream management which supports logical links
between various document components within the data stream and which
explicitly identifies the purpose of each link so that the link may be
selectively processed or ignored by a receiver.
The foregoing objects are achieved as is now described. A method and system
for managing logical links between document components within a
presentation data stream which includes a continuous ordered stream of
uniquely identified data objects and associated elements is provided. The
processing of presentation form documents has been extended from hard copy
devices into interactive presentation forms which accommodate
sophisticated navigation techniques such as hypertext. In order to
accommodate this process a link logical element (LLE) is defined within
the document presentation data stream which identifies a source component
and a target component for a logical link. Multiple purpose links which
provide navigation linkage, annotation linkage and append linkage are
provided and the link logical element (LLE) further includes a field which
specifies the purpose of a particular link. Optional fields are also
provided which may be utilized to pass parameters to the target component
upon processing the link. In this manner a receiver of the data stream may
selectively process or ignore a particular logical link.
The above as well as additional objectives, features, and advantages of the
present invention will become apparent in the following detailed written
description.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are set forth
in the appended claims. The invention itself, however, as well as a
preferred mode of use, further objectives and advantages thereof, will
best be understood by reference to the following detailed description of
an illustrative embodiment when read in conjunction with the accompanying
drawings, wherein:
FIG. 1 depicts a pictorial representation of a system model relating Mixed
Object Document Content Architecture (MO:DCA) and printer data streams to
a presentation environment;
FIG. 2 is a tabular representation of the syntax of a link logical element
(LLE) structured field utilized in accordance with the method and system
of the present invention; and
FIG. 3 is a high level logic flowchart illustrating a process for
implementing the method of the present invention within a data processing
system.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
With reference now to the figures and in particular with reference to FIG.
1, there is depicted a pictorial representation of a system model relating
Mixed Object Document Content Architecture (MO:DCA) and printer data
streams to a presentation environment. As illustrated, a system 10 is
depicted in which an application 12 can generate a data stream which is
destined for a presentation service 20, an archive service 16 or a viewing
service 18. The so-called "Intelligent Printer Data Stream (IPDS)"
architecture may be utilized to further modify and define the data stream
for utilization by print server programs and device drivers to manage an
all-points-addressable page printing on a full spectrum of devices from
low-end workstations and local area network-attached printers to high
speed, high volume page printers for production jobs, shared printing and
mail room applications. Thus, printer 26 and post processor 28 may utilize
a data stream in the IPDS format.
Referring now to FIG. 2 there is depicted a tabular representation of the
syntax of a link logical element (LLE) structured field utilized in
accordance with the method and system of the present invention. As
depicted at reference numeral 30, the link logical element (LLE)
structured field includes a structured field introducer which specifies
the structured field link, the identity of the structured field, any flags
or bits which may identify whether or not the structured field is
segmented or if a structured field extender or padding is to be utilized,
a two-byte field sequence number utilized to enable users to identify
structured field sequences and the structured field data which provides
the structured field's effect.
The syntax for the link logical element (LLE) structured field data is
shown at reference numeral 32. As depicted, the syntax includes an offset
value in bytes and the type of field. A name for the particular field is
provided, if applicable, and the appropriate range of valid values for
that field are also specified. The meaning or purpose of the data element
is set forth under the column "Meaning". Finally, an indication of whether
or not the field is mandatory or optional and whether or not an exception
code for the exception conditions which are possible for this dead element
is also provided.
Thus, as illustrated within FIG. 2, the link logical element (LLE)
structured field includes the link type (LnkType) which specifies the
purpose of the linkage. As illustrated, the link type may include a
navigation link, an annotation link or an append link. As utilized herein
a navigation link is a link type which specifies the linkage from a source
document component to a contextually-related target document component.
Navigation links may be utilized to support applications such as hypertext
and hypermedia. Next, the link may also comprise a annotation link which
specifies the linkage from a source document component to a target
document component that contains an annotation. Finally, an append link
specifies the linkage from the end of a source document component to a
target document component which contains an append.
Additionally, two or three repeating groups are provided which specify the
repeating group length, indicating the total length of a particular
repeating group (RGLength) and the repeating group function (RGFunct)
which identifies the function of the repeating group. The repeating group
function may specify the link attribute, the link source and the link
target for a particular logical link. Thus, every link logical element
(LLE) structured field must contain one repeating group which specifies
the source of the logical link, and one repeating group which specifies
the target of the logical link. Every link logical element (LLE)
structured field may also optionally contain one additional repeating
group which specifies attributes of the link.
The optional attribute repeating group can be utilized to specify
attributes and data that applied to the whole link, such as the name of
the link logical element (LLE) structured field, the code page and
character set utilized to encode character data in the link logical
element (LLE) structured field, and parameter data to be passed from the
source component to the target component or to be associated with the
link. In this manner, for example, search parameters associated with the
source document may be passed to a target document component and utilized
to implement a search for similar or related parameters.
The source and target repeating groups specify the document components that
are the source and target of the link and may further restrict the source
and target to rectangular areas on the corresponding document component
presentation spaces. The source and target repeating groups may qualify
the name of the document component with the names of the document
components that are higher in the document hierarchy. For example, if the
target of the link is a page, the target repeating group may specify the
name of the page, the name of the page group that contains the page, and
the name of the document that contains the page group. If the names of the
document components that are higher in the document hierarchy are not
explicitly specified within the link logical element (LLE) repeating
groups, those names are inherited from the document components that
contain the link logical element (LLE) structured field. For example, if a
source repeating group only specifies an area, then the link logical
element (LLE) structured field must be located within a page or overlay
definition, and the name of the page or overlay, as well as the name of
the document, are inherited by the source repeating group.
In general, source and target repeating groups may specify multiple
document components names, however, within each repeating group the
identified document components must all be part of the same document
hierarchy, and the actual source or target of the link is determined by
the lowest specified member of that document component hierarchy.
In accordance with the method and system of the present invention the
document components which may be specified as source or target components
include the document, the page group, the page, the overlay, a process
element (such as a logical tag element), a rectangular area or other
object data such as non-native data objects which do not conform to the
Mixed Object Document Content Architecture (MO:DCA).
Additionally, various triplets may appear in the link logical element (LLE)
structured field within the repeating groups to specify a coded graphic
character set global identifier, a fully qualified name for a process
element, an object classification, measurement units or an area definition
which defines a rectangular area on the presentation space of the lowest
document component in the document hierarchy that is specified by the
repeating group or that is inherited by the repeating group. Additionally,
as set forth above, parameters to be utilized by the target component may
be passed from the source component, within the optional triplets. If the
repeating group does not explicitly specify an object, then the object
specification is inherited from the document hierarchy, as set forth
above. Thus, an area definition will be defined on the presentation space
for the page which contains a link logical element (LLE) structured field
and the units of measurement for resolving the offset and size of the area
are specified by a measurement unit triplet, as described above.
Thus, as those skilled in the art will appreciate upon reference to the
foregoing, by specifying the source and target components for a logical
link and specifying the purpose of the logical link, the efficiency of
processing a presentation data stream may be greatly enhanced by
permitting the receiver to elect to process or ignore a logical link,
having been made aware of the purpose of that logical link utilizing the
link logical element (LLE) structured field described herein.
With reference now to FIG. 3, there is illustrated a high level logic
flowchart which depicts a process for implementing the method of the
present invention within a data processing system. As illustrated, this
process begins at block 34 and thereafter passes to block 36. Block 36
illustrates a determination of whether or not a link logical element (LLE)
has been encountered during the processing of a presentation data stream.
If not, the process merely iterates until such time as a link logical
element (LLE) is encountered.
Still referring to block 36, in the event a link logical element (LLE) is
encountered, the process passes to block 38. Block 38 illustrates the
identification of the source component for the specified logical link. The
process then passes to block 40 which illustrates the identification of
the target component for the logical link.
Next, the process passes to block 42 which depicts a determination of the
purpose for the specified logical link. That is, whether or not the
logical link is a navigation link, an annotation link, or an append link.
Thereafter the process passes to block 42. Block 42 illustrates a
determination by the receiver of the data stream whether the identified
logical link is to be processed. If not, the process merely returns to
block 36, in an iterative fashion. However, in the event the identified
logical link is to be processed is illustrated in block 44. If so, the
process passes to block 46. Block 46 illustrates the processing of the
link utilizing any parameters passed from the source document counterpart
to the target document counterpart and the process then passes to block 48
and returns.
Upon reference to the foregoing those skilled in the art will appreciate
that the method and system described herein provide an efficient technique
whereby logical links between various document components within a
presentation data stream may be maintained, managed and specified such
that a receiver of the presentation data stream may elect to process or
ignore such logical links based upon a determination of the purpose of the
link, as specified within the link logical element (LLE) structured field
of the present invention.
While the invention has been particularly shown and described with
reference to a preferred embodiment, it will be understood by those
skilled in the art that various changes in form and detail may be made
therein without departing from the spirit and scope of the invention.
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