JP2004258773A - Document compressing device and document reconstructing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document compressing device which can compress an XML document in such a manner that the XML document can be easily reconstructed without a dedicated application. <P>SOLUTION: The document compressing device is configured to compress an element specified by an XML document analyzing part 12, provide an XML document compressing part 13 which creates a correspondence list indicating the correspondence relationship between before and after compression of the element, and create an XSLT 4 for reconstruction for reference when the compressed element is reconstructed based on the correspondence list created by an XML document compressing part 13. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a document compression apparatus for compressing a structured document such as an XML document and a document restoration apparatus for restoring the compressed structured document.
[0002]
[Prior art]
In recent years, with the spread of the Internet, opportunities for exchanging various electronic data via the Internet have increased. At that time, XML is increasingly used as a data exchange method.
XML is a document in a format in which data "elements" are sandwiched between a start tag and an end tag. Since the content of the element can have another element, a nested hierarchical structure is realized. be able to. Elements can also have “attributes”.
<Element name> Element content </ Element name>
<Element name attribute name = "attribute value"> element content </ element name>
[0003]
However, when a long name is specified for an element name or an attribute name, data redundancy increases and data capacity increases.
Therefore, a document compression apparatus for compressing an XML document is disclosed in Patent Document 1 below. However, when a conventional document compression apparatus compresses an XML document, if there is no dedicated application, the XML document is restored. Can not.
[0004]
[Patent Document 1]
JP 2001-67348 A (paragraph numbers [0050] to [0065], FIG. 1)
[0005]
[Problems to be solved by the invention]
Since the conventional document compression apparatus is configured as described above, the data volume can be reduced by compressing the XML document. However, without a dedicated application, the XML document cannot be restored. There is a problem that it is not suitable for exchanging XML documents using the Internet or the like.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. When an XML document is compressed, the compression is performed in such a format that the XML document can be easily restored without a dedicated application. It is an object of the present invention to obtain a document compression apparatus capable of performing the above.
Another object of the present invention is to provide a document restoring apparatus capable of easily restoring an XML document without a dedicated application.
[0007]
[Means for Solving the Problems]
The document compression apparatus according to the present invention includes an element compression unit that compresses the element specified by the element specification unit and creates a correspondence table indicating a correspondence relationship between the element before and after the compression. Based on the correspondence table, a template to be referred to when the compressed element is restored is generated.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 is a system configuration diagram showing a system to which a document compression apparatus and a document decompression apparatus according to Embodiment 1 of the present invention are applied. In FIG. 1, a document compression apparatus 2 inputs an original 1 of an XML document and The original document 1 is compressed, and a restoring XSLT 4 to be referred to when the compressed XML document 3 is restored is generated.
Upon receiving the compressed XML document 3 and the restoring XSLT 4 from the document compression device 2 via the network 5, the document restoring device 6 refers to the restoring XSLT 4 to restore the original document 1 of the XML document.
[0009]
FIG. 2 is a configuration diagram showing the document compression apparatus 2 according to the first embodiment of the present invention. In the figure, an XML document input unit 11 inputs an XML document that is a structured document. The XML document analysis unit 12 analyzes the structure of the XML document input by the XML document input unit 11 and specifies an element to be compressed. Note that the XML document analysis unit 12 constitutes an element specifying unit.
The XML document compression unit 13 compresses the element specified by the XML document analysis unit 12 and creates a correspondence table indicating the correspondence of the element before and after compression. Note that the XML document compression unit 13 constitutes element compression means. The XSLT generating unit 14 generates a restoring XSLT 4 that is referred to when restoring the compressed element based on the correspondence table created by the XML document compressing unit 13. Note that the XSLT generation unit 14 forms a template generation unit.
The XML document transmitting unit 15 transmits the compressed XML document 3 to the document restoring device 6 via the network 5, and the XSLT transmitting unit 16 restores the restoring XSLT 4 generated by the XSLT generating unit 14 via the network 5. Transmit to the device 6.
[0010]
FIG. 3 is a block diagram showing a document restoring device 6 according to the first embodiment of the present invention. In FIG. 3, an XML document receiving unit 21 receives a compressed XML document 3 transmitted from the document compressing device 2 and performs XSLT The receiving unit 22 receives the decompressing XSLT 4 transmitted from the document compression device 2. The XML document receiving unit 21 and the XSLT receiving unit 22 constitute an input unit.
The XML document restoring unit 23 refers to the restoring XSLT 4 received by the XSLT receiving unit 22 and restores the compressed XML document 3 received by the XML document receiving unit 21. Note that the XML document restoring unit 23 constitutes an element restoring unit.
The XML document output unit 24 outputs the XML document restored by the XML document restoration unit 23.
FIG. 4 is a flowchart showing the processing contents of the XML document analysis unit 12 and the XML document compression unit 13, and FIG. 9 is a flowchart showing the processing contents of the XSLT generation unit 14.
[0011]
Next, the operation will be described.
First, when the XML document input unit 11 of the document compression apparatus 2 inputs the original document 1 of the XML document, the XML document analysis unit 12 analyzes the structure of the XML document input by the XML document input unit 11 and generates a compression target element. To identify.
The XML document compression unit 13 compresses the element specified by the XML document analysis unit 12 and creates a correspondence table indicating the correspondence of the element before and after compression.
[0012]
Specifically, it is as follows.
First, the structure information and the contents of the XML document are expanded on the memory to generate a DOM tree (step ST1), and a pointer indicating a processing target is designated as a root element of the XML document (step ST2).
For example, when an XML document as shown in FIG. 5A is input by the XML document input unit 11, the processing target pointer is designated as a root element <products>.
[0013]
Next, the XML document analysis unit 12 checks whether or not the root element <products> has an unprocessed child element (step ST3), and determines whether the root element <products> has an unprocessed child element. If so, the processing target pointer is shifted from the root element <products> to the child element (step ST4).
In this example, since the root element <products> has <product id = "0001"> as an unprocessed child element, as shown in FIG. 5B, the processing target pointer is set to <product id = <0001 >>.
[0014]
Further, the XML document analysis unit 12 checks whether or not the migrated element <product id = "0001"> has an unprocessed child element (step ST3), and the migrated element <product id = If “0001”> has an unprocessed child element, the processing target pointer is shifted from the element <product id = “0001”> to the child element (step ST4).
In this example, since the element <product id = "0001"> has <name> as an unprocessed child element, the processing target pointer is shifted to <name> as shown in FIG. I do.
[0015]
Next, since the element <name> after the migration does not have an unprocessed child element, the XML document analysis unit 12 checks whether the element <name> has an unprocessed attribute. (Step ST5).
In this example, since the element <name> has no unprocessed attribute, the XML document compression unit 13 shortens the element name of the element <name> as shown in FIG. 5D (step ST6). ). The element name is shortened as "name" → "a".
When the element names are shortened in this way, the XML document compression unit 13 creates a correspondence table indicating the correspondence between the element names before and after the shortening, as shown in FIG.
[0016]
Next, the XML document analysis unit 12 checks whether the element <name> has a parent element (step ST7), that is, checks whether the element <name> is a root element. Since the element <name> is not the root element, it is checked whether the element <name> has an attribute or a child element (step ST8).
In this example, since the element <name> has neither an attribute nor a child element, it is confirmed whether or not the parent element <product id = "0001"> has the content (step ST9). .
In this example, since the parent element <product id = “0001”> has no content, the XML document compression unit 13 sets the start tag of the element <name> as shown in FIG. The end tag is deleted, and the content "ABC" of the element is added as an attribute of the parent element (step ST10). That is, the element <name> is deleted, and the parent element is changed to <product id = “0001” a = “ABC”>.
[0017]
When the XML document compression unit 13 performs the element compression process and updates the correspondence table as described above (step ST11 or ST12), the XML document analysis unit 12 shifts the processing target pointer to the parent element (step ST13). ), By returning to the processing of step ST3, the same processing as described above is repeatedly executed.
Thus, in this example, after the element name of the element <price> is shortened from “price” to “b”, the start tag and the end tag of the element <price> are deleted, and the element <price> is deleted. The element content "1000" is added as an attribute of the parent element.
As a result, the parent element has no child element, so that the end tag </ product> of the parent element is changed to an empty element tag “/” as shown in FIG. That is, it is changed as <product id = “0001” a = “ABC” b = “1000” />.
[0018]
Thereafter, when the processing target pointer moves to the parent element <product id = “0001” a = “ABC” b = “1000” /> (step ST13), the parent element <product id = “0001” a = “ABC” b Since “=“ 1000 ”/> has no unprocessed child element (step ST3), it is checked whether the XML document analysis unit 12 has an unprocessed attribute (step ST5).
Since the parent element <product id = “0001” a = “ABC” b = “1000” /> has an unprocessed attribute “id”, the XML document compression unit 13 shown in FIG. Thus, the attribute name is shortened (step ST14). The attribute names are shortened, such as "id" → "c".
When the attribute names are shortened in this way, the XML document compression unit 13 creates a correspondence table indicating the correspondence between the attribute names before and after the shortening, as shown in FIG.
[0019]
After that, when the element <product c = “0001” a = “ABC” b = “1000” /> has no unprocessed attribute, the XML document compressing unit 13 performs the following processing as shown in FIG. The element name of the element <product c = “0001” a = “ABC” b = “1000” /> is shortened (step ST6). The element name is shortened, such as "product" → "d".
When the element names are shortened in this way, the XML document compression unit 13 creates a correspondence table indicating the correspondence between the element names before and after the shortening, as shown in FIG.
[0020]
Thereafter, when the processing target pointer moves to the root element <products> (step ST13), the XML document compression unit 13 shortens the element name of the root element <products> as shown in FIG. 5 (i). The element names are shortened, such as "products" → "e".
When the element names are shortened in this way, the XML document compression unit 13 creates a correspondence table indicating the correspondence between the element names before and after the shortening as shown in FIG. 8 (step ST16).
[0021]
When the XML document compression unit 13 completes the compression processing of the XML document as described above, the XSLT generation unit 14 restores the compressed elements based on the correspondence tables created at that time in FIGS. Then, a restoring XSLT 4 to be referred to when performing the process is generated (step ST17).
That is, leaf elements (elements having no attribute or child element) and attributes converted as attributes are described as an XSLT template, and an element serving as a parent element is described as a template that describes application of a template to a child element. . Specifically, it is as follows.
[0022]
First, the XSLT generation unit 14 uses each element of the correspondence table in FIG. 6 as an XSLT template (step ST21).
Next, the XSLT generation unit 14 uses each attribute of the correspondence table of FIG. 7 as an XSLT template (step ST22).
Next, the XSLT generation unit 14 uses each element of the correspondence table in FIG. 8 as an XSLT template (step ST23).
[0023]
Next, the XSLT generation unit 14 searches for the attribute belonging to the corresponding element from the correspondence table in FIG. 7, and applies the template (step ST24).
Next, the XSLT generation unit 14 searches for a leaf element belonging to the corresponding element from the correspondence table in FIG. 6, and applies the template (step ST25).
The XSLT generation unit 14 repeatedly executes the processing of steps ST24 and ST25 until a template is created for all elements in the correspondence table of FIG. 8 (step ST26).
FIG. 10 shows an example of the restoration XSLT 4 generated by the XSLT generation unit 14.
[0024]
The XML document transmitting unit 15 transmits the compressed XML document 3 to the document restoring device 6 via the network 5, and the XSLT transmitting unit 16 transmits the restoring XSLT 4 generated by the XSLT generating unit 14 to the document via the network 5. The data is transmitted to the restoration device 6.
[0025]
On the other hand, the XML document restoring unit 23 of the document restoring device 6 receives the compressed XML document 3 transmitted from the document compressing device 2 by the XML document receiving unit 21, and transmits the XML document 3 transmitted from the document compressing device 2 by the XSLT receiving unit 22. When the restored XSLT 4 is received, the compressed XML document 3 is restored with reference to the restored XSLT 4.
That is, in the decompression process, the compressed XML document 3 is decompressed by sequentially executing the description contents of the decompression XSLT 4 described in the XML document format. FIG. 11 shows the contents of the restoration processing, and FIG. 11 (k) corresponds to the restored XML document.
[0026]
As is clear from the above, according to the first embodiment, the XML document compression unit that compresses the element specified by the XML document analysis unit 12 and creates a correspondence table indicating the correspondence between the element before and after the compression. 13 is configured to generate the restoring XSLT 4 that is referred to when restoring the compressed element based on the correspondence table created by the XML document compressing unit 13. Thus, it is possible to compress the XML document in a format that can easily restore the XML document without the application.
Further, according to the first embodiment, the configuration is such that the elements of the XML document compressed by the document compression device are restored with reference to the decompression XSLT 4 generated by the document compression device. Even if there is no XML document, it is possible to easily restore the XML document.
[0027]
According to the first embodiment, when the element specified by the XML document analysis unit 12 has no attribute and no child element, the start tag and the end tag of the element are deleted, and the content of the element is changed to the attribute of the parent element. Since the configuration is such that the XML document is added, the capacity of the XML document can be reduced.
According to the first embodiment, when the element specified by the XML document analysis unit 12 does not have a child element but has an attribute, the attribute name is shortened, and the correspondence between the attribute names before and after the shortening is reduced. Is generated so that the capacity of the XML document can be reduced and the XML document can be easily restored.
[0028]
Further, according to the first embodiment, by deleting the start tag and end tag of an element and adding the content of the element as an attribute of the parent element, when the parent element has no child element, Is changed to an empty element tag, so that the capacity of the XML document can be reduced.
According to the first embodiment, the element name and the attribute name of the parent element are shortened, and the correspondence table indicating the correspondence between the element name and the attribute name before and after the shortening is created. It is possible to reduce the size of the document and to easily restore the XML document.
[0029]
【The invention's effect】
As described above, according to the present invention, the element specified by the element specifying means is compressed, and the element compression means for creating a correspondence table indicating a correspondence relationship between before and after the compression of the element is provided. Since the template to be referred to when restoring the compressed element is generated based on the created correspondence table, when the XML document is compressed, the XML document can be easily restored even if there is no dedicated application. There is an effect that compression can be performed in a format that can be performed.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a system to which a document compression device and a document decompression device according to a first embodiment of the present invention are applied;
FIG. 2 is a configuration diagram showing a document compression apparatus according to Embodiment 1 of the present invention.
FIG. 3 is a configuration diagram showing a document restoration device according to the first embodiment of the present invention.
FIG. 4 is a flowchart showing processing contents of an XML document analysis unit and an XML document compression unit.
FIG. 5 is an explanatory diagram showing processing contents of a compression processing.
FIG. 6 is an explanatory diagram showing a correspondence table between leaf element names and short character strings.
FIG. 7 is an explanatory diagram showing a correspondence table between attribute names and short character strings.
FIG. 8 is an explanatory diagram showing a correspondence table between element names and short character strings.
FIG. 9 is a flowchart illustrating processing performed by an XSLT generation unit;
FIG. 10 is an explanatory diagram showing a restoring XSLT.
FIG. 11 is an explanatory diagram illustrating processing contents of a restoration processing;
[Explanation of symbols]
1 original document of XML document, 2 document compression device, 3 compressed XML document, 4 restoration XSLT, 5 network, 6 document restoration device, 11 XML document input unit, 12 XML document analysis unit (element specifying means), 13 XML Document compression unit (element compression unit), 14 XSLT generation unit (template generation unit), 15 XML document transmission unit, 16 XSLT transmission unit, 21 XML document reception unit (input unit), 22 XSLT reception unit (input unit), 23 An XML document restoring unit (element restoring unit) and a 24 XML document outputting unit;

Claims (6)

Analyzes the structure of the structured document and creates an element identification unit that identifies the element to be compressed, and a correspondence table that compresses the element identified by the element identification unit and shows the correspondence of the element before and after compression A document compression apparatus comprising: an element compression unit that performs compression; and a template generation unit that generates a template to be referred to when restoring the compressed element based on the correspondence table created by the element compression unit. When the element specified by the element specifying means has no attribute and no child element, the element compressing means deletes a start tag and an end tag of the element and adds the content of the element as an attribute of the parent element. 2. The document compression apparatus according to claim 1, wherein: When the element specified by the element specifying means does not have a child element but has an attribute, the element compressing means shortens the attribute name and creates a correspondence table indicating a correspondence relationship between the attribute names before and after the shortening. The document compression apparatus according to claim 1, wherein: The element compression means deletes the start tag and the end tag of the element and adds the content of the element as an attribute of the parent element. When the parent element has no child element, the end tag of the parent element is set to an empty element. 3. The document compression apparatus according to claim 2, wherein the apparatus is changed to a tag. 3. The document compression apparatus according to claim 2, wherein the element compression unit shortens the element names and the attribute names of the parent element and creates a correspondence table indicating the correspondence between the element names and the attribute names before and after the shortening. . Input means for inputting a structured document whose elements have been compressed by the document compression apparatus and a template generated by the document compression apparatus; and decompressing the compressed elements by referring to the template input by the input means. Document restoring device, comprising:

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