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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of document layout process for
generating a layout structure of a document on the basis of a logical
structure of the document, and a document processing system for embodying
the method.
2. Description of the Related art
Conventional document processing techniques (which will be sometimes
referred to as the layout process) for generating a layout structure of a
document on the basis of a logical structure of the document include, for
example, an ODA technique (ISO8613: Information Processing-Text and Office
Systems Open Document Architecture (ODA) and Interchange Format (1989))
and a TNT technique (J. Andere, R. Furuta, V. Quint: Structured Documents,
Cambridge University Press (1989)). In these techniques, layout process is
carried out on the basis of a restriction condition (which will be
sometimes referred to as the `layout directive restriction`) relating to
the layout of logical objects in a logical structure and a restriction
condition (which will be sometimes referred to as the `structure
generation restriction`) wherein a candidate for generating a layout
structure is described.
The layout directive restriction is, for example, that "all structures
below this logical object must be laid out in a specific frame."
The structure generation restriction is, for example, that "this page
contains within the page a body frame and if necessary, a footnote frame."
The layout process must be carried out while satisfying two sorts of such
layout directive and structure generation restrictions. However, there are
many candidates for the generatable layout structure and whether or not
the layout structure is suitable depends on the amount of contents of a
logical structure to be laid out and also on the layout directive
restriction. For this reason, given the document logical structure and the
two sorts of restrictions, it is difficult for a processor taking a role
of layout process to infer a suitable layout structure on the basis of
these data.
For the purpose of overcoming this difficulty, there has been considered
such a document processing system based on try and error manner that one
of candidates for a layout structure is selected for layout and if the
layout process ends in a failure, then the processing is returned (which
will be referred to as the backtrack, hereinafter) to such a state as to
allow selection of another candidate to retry the layout process and then
the layout process is restarted.
Such document processing system is well known and disclosed in literatures
(proceedings), for example, in 1) a paper titled "A Prototype of ODA
Document Processing System (3)--Layout Process--" reported by Hayashi,
Saito, Ishida and Murata in Proceedings (Sep. 12, 1988) of the 37-th
General Meeting of the Information Processing Society of Japan, 2) a paper
titled "A Method of Document Layout Process based on ODA (1)--Issues on
Backtrack" reported by Murayama, Yamaguchi, Matsudaira, Uhehara and
Kayimasa in Proceedings (Mar. 14, 1990) of the 40-th Annual Convention of
the Information Processing Society of Japan, 3) a paper titled "A Method
of Document Layout Process Based on ODA (2)--A Consideration of
Efficiency" reported by Matsudaira, Yamaguchi and Uhehara in Proceedings
(Mar. 14, 1990) of the 40-th Annual Convention of the Information
Processing Society of Japan, and 4) a paper titled "A Method of Document
Layout Process Based on ODA (3)--Processing Repetitive Construction"
reported by Yamaguchi, Matsudaira, Uhehara and Kagimasa in Proceedings
(Mar. 14, 1990) of the 40-th Annual Convention of the Information
Processing Society of Japan.
In such document processing systems as disclosed in such proceeding
literatures, it is considered that erroneous selection might be carried
out several times in the course of generating a layout structure but a
right layout structure satisfying the restriction conditions can
eventually be non-manually or automatically generated.
In the above respective document processing systems, however, for the
purpose of returning to such a state as to allow selection of another
candidate, an alternate candidate is generated on the basis of the
structure generation restriction, that is, consideration is paid only to
the layout structure and no consideration is not paid at all to that
position in the logical structure from which layout process is restarted.
This involves a problem when re-layout process is required because a
structure to be alternated is generated on the basis of the layout
directive restriction.
Explanation will next be made as to a detailed example of he re-layouting
problem by referring to FIGS. 9 and 13.
In FIG. 9, a part above a chain-dotted line A denotes a logical structure
while a part below the line A denotes the contents of a document. In each
of FIGS. 10 to 13, a part above a chain-dotted line A denotes a logical
structure, a part below a chain-dotted line B denotes a layout structure,
and a part sandwiched by the lines A and B therebetween denotes the
contents of a document. In this connection, the logical structure and the
document contents in each drawing are the same as the counterparts in FIG.
9.
In FIGS. 9 to 13, further, `logical root`, `chapter 1`, `section 1.1`,
`section 1.2`, `chapter 2`, `section 2.1`, `section 2.2` and `section 2.3`
represent respectively a logical object, whereas `layout root`, `page 1`,
`frame 1`, `block 1--1`, `block 1-2`, `page 2`, `frame 2`, `block 2-1`,
`block 2--2`, `page 2'`, `frame 2'`, `block 2'-1` and `block 2'-2`
represent respectively a layout object.
Assume now that layout process is carried out as shown by a logical
structure in FIG. 9. Then, since the `chapter 2` logical object has a
`page change` layout directive restriction, the document processing
system, when it is desired to lay out the `chapter 2` logical object,
generates a new page and adds it to the layout structure.
And the document processing system performs its layout process in such a
manner that the contents linked to the lower structure of the `chapter 2`
logical object are laid out from its page.
Assume now that, in the course of laying out the contents of the `chapter
2`, a backtrack took place for some reason and page 2 was alternated in
such a layout state as shown, for example, in FIG. 11. In this case,
layout process must be restarted originally from the logical object
(`chapter 2` logical object in FIG. 11) having the `page change` layout
directive restriction. However, this prior art system cannot clearly find
the logical object for the layout process to be restarted. For this
reason, in the prior art system, the logical object linked to the contents
laid out for the beginning of the page to be alternated, that is, the
`section 2.1` logical object might be selected as the logical object to be
restarted as shown in FIG. 12. In this case, the `page change` layout
directive restriction imposed on the `chapter 2` logical object is not
applied to the `section 2.1` logical object so that the leading contents
of the `chapter 2` are laid out for the page (page 1) preceding the
alternate candidate page (page 2) as shown in FIG. 13.
In this way, the prior art method of layout process has had such a problem
that, since no consideration is taken as to the fact that the alternate
candidate selection influences what layout directive restriction, it is
impossible to select the alternate candidate always correctly.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of
document layout process which can accurately determine an alternate
candidate to a layout structure and also a system embodying the same
method.
In accordance with an aspect of the present invention, the above object is
attained by a document processing system which comprises detection means
for detecting the fact that the layout structure of the document being
generated does not conform to predetermined restriction conditions on the
document layout, and backtrack range decision means, when the detection
means detects an unconformity between the layout structure and the
predetermined restriction conditions, for deciding desired one of
constituent elements forming the logical structure of the document taking
a backtrack influence range into consideration for restart of the layout
process.
In the present invention, while such a layout structure of the document as
to conform to the restriction conditions is generated, if the layout
structure comes to an unconformity to the restriction conditions, then the
system determines desired one of the constituent elements of the logical
structure for the layout process to be restarted, taking the backtrack
influence range into consideration. Therefore, generation and deletion of
unnecessary layout structures can be minimized.
Other objects and effects of the present invention will be easily
appreciated from the following detailed explanation and the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a functional block diagram of a document processing system in
accordance with an embodiment of the present invention:
FIG. 2 is a functional block diagram showing the system of FIG. 1, in
particular, detailing particular parts of the system;
FIG. 3 is a flowchart for explaining the detecting process of the present
embodiment;
FIG. 4 is a flowchart for explaining the backtrack range determining
process of the present embodiment;
FIGS. 5 to 8 are diagrams for explaining the layout restarting procedure of
the present embodiment respectively; and
FIGS. 9 to 13 are diagrams for explaining the layout restarting procedure
of a prior art document processing system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention will be described with reference to
the attached drawings.
Referring first to FIG. 1, there is shown a functional block diagram of a
document processing system in accordance with an embodiment of the present
invention, in which layout process is carried out based on the
aforementioned ODA (Open Document Architecture: (ISO 8613). The document
processing system according to the present invention may be applied also
to such an apparatus having a document processing function as, for
example, a document processing apparatus, a workstation or a word
processor.
In FIG. 1, the document processing system includes a logical structure
holding means 1 for holding the logical structure of a document, a layout
structure holding means 2 for holding the layout structure of the
document, a restriction holding means 3 for holding restriction conditions
(including the aforementioned layout directive and structure generation
restrictions) on the document layout process, a layout-structure
generating means for generating an allocating structure on the basis of
the logical structure, a detection means 5 for detecting the fact that the
layout structure being generated fails to satisfy the above restriction
conditions, a backtrack means 6 for performing again its layout process
when the detection means 5 detects the failure of the layout structure to
satisfy the above restriction conditions, and a backtrack range deciding
means for determining a desired logical arrangement to be subjected to a
layout restart on the basis of the constituent elements of the logical
structure.
Shown in FIG. 2 is a functional block diagram of the document processing
system of FIG. 1, showing, in particular, the details of the detection
means 5 and the backtrack range deciding means 7 in FIG. 1. More
specifically, the detection means 5, as illustrated, comprises a
correspondence means 51 for making a correspondence between a logical
object, a layout object and a layout directive attribute name and for
storing the correspondence therein, an inspection target memory means 52
for storing therein the logical object to be inspected, an inspection
target changing means 53 for changing the logical object to be inspected
by referring to the data of the logical structure holding means 1, an
empty-structure decision means 54 for determining the presence or absence
of a structure in which no layout process is carried out for subordinate
objects of a certain layout object, a logical hierarchical relation
decision means 55 for determining whether or not a logical object is
included in a subordinate structure of another logical object by referring
to the data of the logical structure holding means 1, a layout
hierarchical relation decision means 56 for determining whether or not a
layout object is included in a subordinate structure of another layout
object, and a detection process control means 57 for performing data
transfer with the layout structure generating means 4 and the backtrack
means 6 and also for controlling the same means 4 and 6 to control a
detection process.
In the present embodiment, inspection of the detection means 5 about
whether or not to satisfy the layout directive attribute is roughly
divided into two stages.
In the first stage, it is checked whether or not "when contents to be
subjected to layout process becomes null with respect to subordinate
layout objects of the layout object selected as satisfying a `layout
object class` attribute, any of the subordinate layout objects remains
still."
In the second stage, it is checked whether or not "when contents to be
subjected to layout process is still present with respect to the
subordinate layout objects of the layout object selected as satisfying the
`layout object class` attribute, an `indivisibility` attribute or a `same
layout object` attribute, layout process takes place with respect to
layout objects other than the above subordinate layout objects."
In this connection, the above `layout object class`, `indivisibility` and
`same layout object` attributes as well as a `new layout object` attribute
to be explained later form a part of the attributes of the layout
directive restriction defined based on the aforementioned ODA. One or ones
of these attributes may be associated with a logical object.
On the other hand, the backtrack range deciding mean 7 comprises a
correspondence means 71 for making a correspondence between a layout
object and a logical object and storing the correspondence therein, a
target layout object memory means 72 for storing therein a layout object
to be alternated by a backtrack, a target logical object memory means 73
for storing therein a logical object allocated in association with the
layout object stored in the target layout object memory means 72, a target
logical order retrieval means 74 for retrieving one of the logical objects
stored in the target logical object memory means 73 which is the first in
the logical order, and a range decision process control means 75 for
performing data transfer with the layout structure generating means 4 to
control the above respective means and also a decision process determining
a backtrack influence range.
In the present embodiment, the logical structure holding means 1, layout
structure holding means 2, restriction holding means 3, inspection target
memory means 52, target layout object memory means 72 and target logical
object memory means 73 comprise respectively a memory.
The layout structure generating means 4, backtrack means 6, correspondence
means 51, inspection target changing means 53, empty structure decision
means 54, logical hierarchical relation decision means 55, layout
hierarchical relation decision means 56, detection process control means
57, correspondence means 71, logical order retrieval means 74 and range
decision process control means 75 may be realized, for example, by a
central processing unit executing software (program) for carrying out the
respective functions of the above means. Of course, these means may be
realized in the form of hardware or firmware.
With the aforementioned arrangement, explanation will next be made as to
the detecting process of the document processing system by referring to
the flowchart of FIG. 3.
In more detail, the layout structure generating means 4 first selects
non-layout one of the logical objects stored in the logical structure
holding means 1 and then examines the layout structure holding means 2 and
the restriction holding means 3 to select one of the layout objects stored
in the layout structure holding means 2 which is suitable as a layout
destination for the above selected logical object. This means to utilize
the layout structure already stored in the layout structure holding means
2. An example of such layout-structure utilizing method is to utilize a
minimum layout structure common to all specific layout structures
generatable from a layout structure (corresponding to the generic layout
structure according to the ODA). This minimum layout structure is
disclosed in Japanese Patent Application. No. 2-157068 filed on Jun. 15,
1990 in Japan.
The layout structure generating means 4, in the case where there is not
present a suitable layout object in the layout structure holding means 2,
generates a suitable layout object based on the restriction conditions
held in the restriction holding means 3 and stores it in the layout
structure holding means 2. Next, the layout structure generating means 4
selects a logical object and a layout object as a candidate for the layout
destination of the logical object and sends a start signal to the
detection means 5. The detection means 5, when receiving the start signal
from the means 4, examines whether or not the layout structure so far laid
out satisfies the restriction conditions, because the reception of the
start signal means to get a control authority of the entire layout
process.
In the present embodiment, the logical and layout objects selected by the
layout structure generating means 4 are also referred to as the `selected
logical` and `selected layout` objects, respectively.
The detection means 5 having gotten the control authority of the entire
layout process first executes the first stage inspection. More
specifically, the detection process control means 57 initializes an object
to be inspected, and then inquires of the layout structure generating
means 4 about the `selected logical` object. The detection process control
means 57, when receiving an inquiry result from the layout structure
generating means 4, orders the inspection target changing means 53 to
store a logical object preceded by one (in the logical order) with respect
to the `selected logical` object in the inspection target memory means 52.
This causes, as shown in FIG. 3, the inspection target changing means 53 to
retrieve the logical structure holding means 1 store a logical object
conforming to the above instruction in the inspection target memory means
52 (step 101) and then send a signal indicative of the completion of
execution of the instruction to the detection process control means 57.
The means 57, when receiving the signal from the inspection target
changing means 53, orders the logical hierarchical relation decision means
55 to decide whether or not the logical object (which will be referred to
as the `inspection target`, hereinafter) stored in the inspection target
memory means 52 corresponds to the logical object immediately superior to
the `selected logical` object. The logical hierarchical relation decision
means 55 retrieves the logical structure holding means 1 and returns a
result of the instruction to the detection process control means 57 (step
102).
When the returned result is indicative of the fact that the `inspection
target` corresponds to the logical object immediately above the `selected
logical` object, the detection process control means 57 shifts its
inspecting process into the second stage because the first stage
inspection is unnecessary. If not, then the detection process control
means 57 judges whether or not the `inspection target` satisfies a
condition 1 (which will be explained below) (step 103). The condition 1 is
that "the `inspection target` is associated with the layout object by
means of the correspondence means 51 and its correspondence attribute name
is `layout object class`."
When the `inspection target` satisfies the condition 1 in the step 103, the
detection process control means 57 instructs the empty-structure judgement
means 54 to judge whether or not the `inspection target` meets a condition
2 (which will be described later). The empty-structure judgement means 54
responsive to this instruction retrieves the layout structure holding
means 1 and judges whether or not the `inspection target` satisfies the
condition 2 (step 104) and returns its judgement result to the detection
process control means 57.
The condition 2 is that "all the layout objects associated with the
`inspection target` by means of the correspondence means 51 are subjected
to layout process of contents with respect to their subordinate
structures."
When the condition 1 is not satisfied in the step 103 (when it is
unnecessary to inquire of the empty-structure decision means 54) or when
the condition 2 is satisfied in the step 104 (when the detection process
control means 57 knows, as a result of inquiry to the empty-structure
decision means 54, that all the subordinate structures of the layout
objects associated with the `inspection target` are laid out); the
detection process control means 57 instructs the inspection target
changing means 53 to store the immediate superior logical object of the
current `inspection target` as the `inspection target`. The inspection
target changing means 53 retrieves the logical structure holding means 1,
stores a logical object conforming to the instruction order in the
inspection target memory means 52, and sends a signal indicative of the
completion of execution of the instruction to the detection process
control means 57 (step 105). After the processing of the step 105 is
completed, control is returned to the step 102 and the subsequent steps
are executed.
When the condition 2 is not satisfied in the step 104 (when the inquiry
result from the empty-structure decision means 54 indicates that the
subordinate structure of any of the layout objects associated with the
`inspection target` is not laid out), this means that there exists a
remaining layout structure in spite of the fact there is no contents to be
laid out. Therefore, the detection process control means 57 sends a start
signal to the backtrack means 6 to transfer the control authority of the
entire layout process to the backtrack means 6 and to execute its
backtracking process (step 106). The backtracking process will be detailed
later.
A series of such processes (steps 101 to 106) are repeated until the
condition for shifting to the second stage inspection is satisfied. When
the first stage inspection condition is satisfied (YES in the step 102),
the detection process control means 57 carries out the second stage
inspection.
In this second stage inspection, the detection process control means 57
first inquires of the layout structure generating means 4 about the
`selected logical` object and when receiving its inquiry result from the
means 4, instructs the inspection target changing means 53 to store the
`selected logical` object as the `inspection target`. The inspection
target changing means 53 retrieves the logical structure holding means 1,
stores a logical object conforming to the instruction in the inspection
target memory means 52, and sends a signal indicative of the completion of
execution of the instruction to the detection process control means 57
(step 107). The detection process control means 57, when receiving the
signal from the inspection target changing means 53, judges whether or not
the `inspection target` satisfies a condition 3 to be described later
(step 108). The condition 3 is that "the `inspection target` is associated
with the layout object by the correspondence means and no inspection
(second stage inspection) is carried out with respect to the layout
object."
When the condition 3 is satisfied, the detection process control means 57
judges whether or not the attribute name associated with the `inspection
target` is `same layout object` (step 109). If so, then the detection
process control means 57 orders the logical hierarchical relation decision
means 56 to judge whether or not the `selected logical` object satisfies a
condition 4 (to be described below) (step 110). The condition 4 is that
"the `selected logical` object is an object appearing on leftdepth first
search path from the `inspection target`."
When the relationship between the `selected logical` object and the
`inspection target` satisfies the condition 4 in the step 110 or when the
associated attribute name is not the `same layout object` attribute in the
step 109, the detection process control means 57 inquires of the layout
structure generating means 4 about the `selected layout` object and order
the logical hierarchical relation decision means 56 to judge whether or
not the `selected layout` object satisfies a condition 5 (to be described
below) (step 111). The condition 5 is that "the `selected layout` object
is a subordinate layout object of the layout object associated with the
`inspection target` or the `selected layout` object is the same as the
layout object associated with the `inspection target`."
That is, in the step 111, the hierarchical relationship the `selected
layout` object and the layout object associated with the `inspection
target` is judged.
When the logical hierarchical relation decision means 56 determines in the
step 111 that the condition 5 is not met, contents to be laid out with
respect to the subordinate structure of the layout object associated with
the `inspection target` is laid out with respect to a layout object other
than the above layout object. Accordingly, the detection process control
means 57, as in the processing of the step 106, sends a start signal to
the backtrack means 6 to transfer the control authority of the entire
layout process to the backtrack means 6.
When it is determined in the step 111 that the `selected layout` object is
included in the subordinate structure of the layout object associated with
the `inspection target`, this means that the restriction condition is
satisfied. Accordingly, the detection process control means 57 handles the
associated layout object satisfying the condition 3 as an inspected one
(step 112) and further judges whether or not any associated layout object
not inspected yet is present as an `inspection target` (step 113). Since a
logical object may have one or more attributes as the layout directive
restriction imposed thereon according to the ODA, the above process means
to inspect in the step 113 whether or not all attributes related to the
logical object as the `inspection target` are for the associated layout
object satisfying the condition 3.
When it is in the step 113 judged that the associated layout objects have
all been inspected, the detection process control means 57 orders the
logical hierarchical relation decision means 56 to judge whether or not
the immediate superior logical object of the `inspection target` is a
logical root (step 114). If it is a logical root then the second stage
inspection is completed, whereas if it is not a logical root then the
detection process control means 57 orders the inspection target changing
means 53 to store the immediate superior logical object of the `inspection
target` as the `inspection target`. The inspection target changing means
53, when receiving this instruction from the detection process control
means 57, retrieves the logical structure holding means 1, stores a
logical object conforming to the instruction in the inspection target
memory means 52 (step 115), and sends a signal indicative of the
completion of execution of the instruction to the detection process
control means 57.
The detection process control means 57 performs such a series of processes
(steps 108 to 114) over the current `inspection target`. And in the case
where it is determined in the step 114 to be a logical root (after
completion of the second stage inspection), when the `selected layout`
object is selected to satisfy any of the `layout object class`,
`indivisibility` and `same layout object` attributes, the detection
process control means 57 orders the correspondence means 51 to make
correspondence between the `selected logical` object and the `selected
layout` object together with its layout directive attribute name.
In response to this, the correspondence means 51 makes the correspondence
so as to satisfy the instruction (step 116) and sends a signal indicative
of the completion of execution of the instruction to the detection process
control means 57. The means 57, when receiving the signal from the
correspondence means 51, sends to the layout structure generating means 4
a signal for continuation of the processing to transfer the control
authority of the entire layout process to the layout structure generating
means 4 (step 117). This causes the layout structure generating means 4 to
actually lay out the logical and layout objects being now selected (in
which case it is assumed that the logical object is already laid out). The
layout structure generating means 4, when receiving a signal indicative of
the completion of a backtrack from the backtrack means 6, restarts its
processing from a logical object newly re-selected by the backtrack means
6.
In the aforementioned processing procedure, the first stage inspection is
carried out through the execution of the steps 101 to 105, while the
second stage inspection is carried out through the execution of the steps
107 to 115.
The backtrack means 6 having gotten the control authority examines the
layout structure holding means 2 and the restriction holding means 3 to
search a structure for restarting the layout process. In the case where
the backtrack means 6 finds the corresponding structure, the backtrack
means 6 adds or deletes the layout object with respect to the layout
structure held in the layout structure holding means 2 so as to conform to
the restriction condition held in the restriction holding means 3. In the
event where the backtrack means 6 deletes the layout structure, the means
6 orders the backtrack range deciding means 7 to decide the backtrack
range.
In this case, for the purpose of deciding the backtrack range, the
backtrack range deciding means 7 is required to hold a data relating to
how the layout structure is generated under what layout directives. Thus,
explanation will next be made as to the data holding process of the
backtrack range deciding means 7.
First, assume that the `new layout object`, `layout object class`,
`indivisibility` or `same layout object` attribute of the layout directive
attributes is previously stored in the restriction holding means 3 as a
directive attribute associated with a logical object held in the logical
structure holding means 1. Assume further that the layout structure
generating means 4 finds a layout object suitable as a layout destination
for the logical object from the layout structure holding means 2 or newly
generates the layout object and adds it to the layout structure holding
means 2. Assume in addition that the detection means 5 determines that the
`selected logical` object and the `selected layout` object satisfy all the
restriction conditions in the restriction holding means 3 at the current
time point.
Then the layout structure generating means 4 sends to the range decision
process control means 75 a signal indicative of the completion of
execution of a new layout process. The range decision process control
means 75, when receiving the signal from the layout structure generating
means 4, instructs the correspondence means 71 to make a correspondence
between the `selected logical` object obtained by inquiring of the layout
structure generating means 4 and the `selected layout` object. The
correspondence means 71, after making the correspondence so as to satisfy
the instruction, sends a signal indicative of the completion of the
processing to the range decision process control means 75. The means 75,
when receiving the completion indicative signal from the correspondence
means 71, sends to the layout structure generating means 4 a signal
indicative of the acquisition of a data for range decision.
Explanation will then be made as to the backtrack-range deciding process
when a backtrack takes place, by referring to the flowchart of FIG. 4.
As shown in FIG. 4, the backtrack means 6 having gotten the control
authority, when discarding the layout object (step 201), invokes the range
decision process control means 75 and sends thereto a signal to store the
discarded layout object.
The range decision process control means 75, when receiving the signal from
the backtrack means 6, stores the discarded layout object in the target
layout object memory means 72 (step 202).
And the backtrack means 6, after completing the generation of an alternate
candidate, sends to the range decision process control means 75 a signal
indicative of execution of the range decision.
The range decision process control means 75 receiving the signal from the
backtrack means 6, when the layout object held in the correspondence means
71 is present in the layout objects stored in the target layout object
memory means 72, stores in the target logical object memory means 73 all
the logical objects associated with the layout object (step 203). When a
frame object having block objects as immediate subordinate objects (i.e.,
`lowest level frame object` in an ODA reference model) is present in the
layout objects stored in the target layout object memory means 72, the
range decision process control means 75 stores in the target logical
object memory means 73 all basic logical objects (lowest level logical
objects connected with the contents) having the contents allocated to the
frame object (step 204).
Next, the range decision process control means 75, when completing the
processing for the target layout object memory means 72, orders the
logical order retrieval means 74 to retrieve top one of the logical
objects of the target logical object memory means 73 in the logical order
(step 205) and returns a logical object as its retrieval result to the
backtrack means 6 as a logical object for layout to be restarted (step
206).
The backtrack means 6, when receiving the logical object from the range
decision process control means 75, sends to the layout structure
generating means 4 the received logical object as a newly re-selected
logical object together with a signal indicative of the completion of the
backtrack (step 207). The layout structure generating means 4, when
receiving the signal from the backtrack means 6, restarts its layout
process from the logical object (a desired constituent element for the
layout to be restarted) newly re-selected by the backtrack means 4 (step
208).
Explanation will next be made as to how to solve the problems already
explained in the Paragraph "Description of the Related Art" in accordance
with the present embodiment, referring to FIGS. 5 to 8. In these drawings,
a part above a chain-dotted line A in each drawing denotes a logical
structure, a part below a chain-dotted line B in each drawing denotes a
layout structure, and a part sandwiched by these lines A and B denotes
document contents. In each drawing, the logical structure and the document
contents are the same those of FIG. 9.
According to the ODA, the logical object titled "Chapter 2" in FIG. 10 and
explained in the Paragraph "Description of the Related Art" means that a
layout directive attribute `new layout object having an attribute value
`object type page` is defined with respect to a composite logical object
indicative of the "Chapter 2".
In the present embodiment, when the composite logical object and a page
object are set by the layout structure generating means 4 to be the
`selected logical` object (`chapter 2` in this example) and the `selected
layout` object (`page 2` in this example), a correspondence between these
two objects are made by the correspondence means 51.
FIG. 5 shows an example showing a layout state between a logical structure
when the layout directive attribute `new layout object` having the
attribute value `object type page` is defined for the composite logical
object `chapter 2` and a layout structure associated with the logical
structure. In such a layout state as illustrated, the `chapter 2` logical
object as the `selected layout` object is associated with the `page 2`
layout object as the `selected layout` object.
In such a layout state as shown in FIG. 6, when a backtrack takes place and
the `page 2` layout object (page object) is deleted for some reason, the
corresponding composite logical object (that is, `chapter 2` composite
logical object) and basic logical objects (that is, `section 2.1` and
`section 2.2` basic logical objects) are stored in the logical object
memory means 73. At this time, among the chapter 2` composite logical
object and the `section 2.1` and `section 2.2` basic logical objects, the
composite logical object is the topmost in the logical order. Accordingly,
the `chapter 2` composite logical object is selected as shown in FIG. 7.
When layout process is carried out from such a layout state as shown in
FIG. 7, such a layout state having a layout structure (final layout
structure) with the `new layout object` directive attribute rightly
evaluated as shown in FIG. 8 is generated.
In this way, control is returned back to the logical object (constituent
element) (`chapter 2` composite logical object, in this example) belonging
to the range in which the restriction condition is applied to decide a
logical object (constituent element) for layout to be restarted.
Therefore, in such a layout structure as shown in FIG. 6, eve | | |
