KR100952051B1 - Method and Apparatus for Encoding and Decoding XML Documents Using Path Code - Google Patents

Abstract

The present invention relates to a method and apparatus for encoding and decoding an XML document, and to a method and apparatus for encoding and decoding an XML document using a path code.

The method of encoding an XML document according to the present invention includes retrieving all element tags and attributes having character data directly from an XML document, extracting XPaths of retrieved element tags or attributes, and pre-assigning each extracted XPath. Converting to a path code, and for the XPath of the element tag and attribute converted to the path code, presenting information of appearance of all the element tags included in the XPath.

XML, XPath, path code, appearance information, encoding, decoding

Description

Method and Apparatus for Encoding and Decoding XML Documents Using Path Codes {Method and Apparatus for Encoding and Decoding XML Documents Using Path Code}

The present invention relates to a method and apparatus for encoding and decoding an XML document, and to a method and apparatus for encoding and decoding an XML document using a path code.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunications Research and Development. [Task Management No .: 2006-S-082-02, Title: Development of Custom-made DMB Technology] .

The terrestrial DMB broadcasting environment is not suitable for transmitting a large amount of data due to the narrow bandwidth. Therefore, it is difficult to transfer data in a text format such as an XML document as it is. Accordingly, in a traffic information service such as TPEG, XML-based data information is binary encoded in real time according to the TPEG binary encoding format and transmitted to the DMB broadcasting network.

Among the metadata transmitted to the domestic terrestrial DMB broadcasting network, data represented by XML documents include terrestrial DMB EPG and TPEG, and all of them have standardized binary coding schemes. For example, the binary coding scheme in TPEG and EPG uses the basic structure of tag, length, and data, and tag code is assigned to all elements and attributes. encoding by assigning to an attribute). Therefore, when encoding an XML document, a tag code is assigned to every element written for each layer. Here, as the tag code assignment is repeatedly performed even for unnecessary elements, the compression rate is lost.

1 shows an example of an XML document in a text format. 2 shows the basic structure of binary encoding for XML documents used in TPEG and EPG. FIG. 3 is a diagram for explaining a conventional tag code allocation method for the XML document illustrated in FIG. 1 using FIG. 2.

1 through 3, an XML document includes A, B, C, and D elements.

According to a conventional tag code allocation method in a binary encoding scheme of an XML document, a tag code is assigned to all elements of A, B, C, and D. For example, tag codes "0x02", "0x03", "0x04", and "0x05" are assigned to the A, B, C, and D elements, respectively. The content of each element is encoded. Here, although only the D element has character data, the tag code is assigned to the B and C elements, respectively. This method reduces the compression rate as unnecessary tag code assignment is repeated. Therefore, a more efficient tag code allocation method is required.

The problem to be solved by the present invention is to increase the compression rate by reducing the allocation of unnecessary tag code by assigning a path code to the XPath of some elements selected from the elements and attributes defined in the schema written in XML Schema and all the attributes. An object of the present invention is to provide a method and apparatus for encoding and decoding an XML document.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, a method of allocating a path code in a schema according to the present invention may include assigning a path code unique to each XPath of selected elements among all elements defined in the schema, and uniquely assigning a path code to each XPath of all attributes. Assigning a path code.

According to an aspect of the present invention, there is provided a method of encoding an XML document, the method including: retrieving all element tags and attributes having character data directly from an XML document, extracting an XPath of the retrieved element tag or attribute, and Converting each of the extracted XPaths into a pre-assigned path code, and displaying the appearance information of all the element tags included in the XPath for the XPath of the element tag and the attribute converted into the path code.

The method for decoding an XML document according to the present invention includes extracting a path code from an encoded XML document, retrieving an XPath corresponding to each extracted path code, and an element tag or attribute included in the retrieved XPath. Selectively restoring according to the appearance information.

According to the method of encoding and decoding an XML document using a path code according to the present invention, by allocating a path code to XPaths of selected elements and all attributes selected from elements defined in a schema, unnecessary allocation of tag codes is reduced. Therefore, the compression rate can be increased.

Hereinafter, a method and apparatus for encoding and decoding an XML document according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram showing the configuration of an apparatus for encoding an XML document according to the present invention.

Referring to FIG. 4, the encoding apparatus 110 includes a path code allocator 120 and an XML encoder 130.

The path code allocator 120 receives a schema from the metadata manager 100 and assigns a path code to elements and attributes defined in the schema. That is, the path code allocator 120 assigns a path code to the XPath of some elements and all attributes to generate a path code table.

The XML encoder 130 receives an XML document from the metadata manager 100 and retrieves all element tags and all attributes having character data directly from the XML document. In addition, the XML encoder 130 encodes the XPath of the retrieved element tag and the attribute by replacing the XPath with the path code defined in the path code table.

5 is a block diagram showing the configuration of an apparatus for decoding an XML document according to the present invention.

Referring to FIG. 5, the decryption apparatus 200 includes an XML decoder 210 and an XML document generator 220.

The XML decoder 210 receives a path code table and an encoded XML document. Here, the path code table is generated by a path code allocation method using XPath of elements and attributes.

The XML decoder 210 extracts a path code from the encoded XML document and retrieves an XPath corresponding to the extracted path code from the received path code table. Thereafter, the XML decoder 210 selectively generates the instance tree by restoring the element tag or the attribute according to the appearance information of the element tags included in the searched XPath.

The XML document generator 220 generates an XML document from the generated instance tree.

6 shows a structure of data used when encoding an XML document according to the present invention.

Referring to FIG. 6, the data structure includes a path, a DET-MOI, a length, and a data field. Each path, DET-MOI, and length can basically be represented by 1 byte.

The path code is the only value assigned to the XPath of elements and attributes defined in a schema written in the XML Schema language. Here, the element defines an element tag that can appear in an XML document in the schema, and the attribute declares the attribute of the element tag in the schema and defines the existence of the attribute.

Hereinafter, the path code assignment method of FIG. 7 will be described.

7 is a flowchart for explaining a path code allocation method.

7, the path code allocator receives a schema file (S100).

Subsequently, the path code allocator extracts a component defined in the schema (S101).

Here, a component is an element constituting a schema, and includes attributes and elements.

Subsequently, the path code allocator determines whether the extracted component is an element (S102).

If the extracted component is not an element, the path code allocator determines whether the component is an attribute (S107). If the component is an attribute, the path code allocator allocates a path code to an XPath of the attribute (S108).

Here, the path code allocator selectively assigns a path code when the extracted component is an element, and allocates a path code to all attributes when the extracted component is an attribute.

On the other hand, if the extracted component is an element, the path code allocator checks the definition of the element (S103).

The path code allocator assigns a unique path code to the XPath of the element when the identified element is defined as a global element, simple content, or mixed content (S104, S105). .

Here, the global element means an element defined as a direct child element of the “schema” root element in the schema.

Simple content means a case in which an element directly has character data.

The path code allocator assigns path codes only to elements that are defined as simple content. On the other hand, a path code is not assigned to an XPath of an element located in a hierarchy between a global element and an element having character data, that is, an element defined as element content.

In addition, mixed content means the case where an element can have character data and another child element simultaneously. This mixed content is defined by setting "true" the mixed attribute of the complex type bound to the element in a schema written in XML Schema.

Therefore, the path code allocator may determine whether the corresponding element is defined as mixed content using a mixed attribute value of a complex type.

On the other hand, when the identified element is defined recursively, the path code allocator allocates a unique path code to each XPath of the first element where the cycle starts and the second element where the cycle ends (S106).

Here, the case where an element is defined circularly means that an arbitrary element is repeatedly defined as its own child element or a descendant element.

In this way, the route code allocator allocates the route code for the extracted schema component and repeatedly performs the route code assignment process for the next schema component until the last component is extracted from the schema (S108).

Hereinafter, a path code allocation method according to the present invention will be described in detail.

8 shows an example of a schema created with XML Schema. FIG. 9 is a graphical diagram of the definition of the schema of FIG. 8. FIG. 10 is a path code table showing a path code assigned to the XPath of the elements and attributes of FIG. 9.

8 through 10, the A and E elements 302 and 328 are global elements, and the F, K, I and H elements 308, 320, 326, 332 and 334 are elements having direct character data. admit. And D elements 316, 318, 322, and 324 are circularly defined elements, and G element 330 is an element defined with mixed content.

First, the path code allocator assigns path codes "0x02" and "0x03" to XPath ("/ A", "/ E") of the global elements A and E elements 302 and 328, respectively. When A and E global elements are referred to as local elements (310 and 306), the XPaths (“./B/A” and “./B/E”) of the referenced local elements are respectively “0x08” and “0x06”. Assign ”. In addition, the path code allocator assigns the XPath (“./B/F”, “./K) of the F, K, I and H elements 308, 320, 326, 332, and 334 defined as simple content with character data. Path codes “0x07”, “0x0C”, “0x05”, and “0x06” respectively.

At this time, global elements should be assigned unique path codes that are distinct from each other, and local elements should be assigned unique path codes that are distinct from each other depending on global elements. Thus, it is possible to assign the same path code to local elements defined as descendants of different global elements. That is, different path codes must be assigned to XPaths of the A element 302 and the E element 328, and XPath such as the E, F, A, and D elements that are descendants of the A element 302 and the A element 302. Must be assigned distinct path codes. However, the same path code “0x06” may be assigned to the XPath of the E element 306 that is a child element of the A element 302 and the XPath of the H element 334 that is a child element of the E element 328. Also, when assigning a path code to an XPath, the same path code is assigned to the same XPath. That is, the K elements 320 and 326 have the same XPath (“./K”) and thus assign the same path code (“0x0C”).

The path code allocator then assigns the path code also to the XPath of the circularly defined D element. Path codes are assigned to the XPaths of the first elements 316 and 322 where the circulation starts and the second elements 318 and 324 where the circulation ends.

For example, the path code allocator assigns the path code “0x09” to the XPath (“./C/J/D”) of the D element 316 where the cycle begins, and the XPath of the D element 318 where the cycle ends. Assign the path code "0x0B" to ("./D"). Then, “0x0B” is assigned to the XPath (“./D”) of the D element 322 where the cycle begins, and “0x0B” is assigned to the XPath (“./D”) of the D element 324 where the cycle ends. do. At this time, the same path code (“0x0B”) is assigned to the same XPath (“./D”).

The path code allocator then assigns the path code “0x04” to the XPath (“./G”) of the G element 330 defined as mixed content. And it assigns only a predetermined fixed value (for example, 0x01) which shows that the character data which the element has is character data of mixed content.

In addition, the path code allocator assigns a path code to each XPath of all attributes defined in the schema. For example, the path code allocator assigns the path code “0x05” to the XPath (“./B/@x”) of the x attribute of the B element 304 and the XPath (“./” of the z attribute of the D element 316. @z ”) to assign the path code“ 0x0A ”.

The above-described path code assignment method assigns a path code to the XPath of some selected elements among all elements, and does not assign a path code to each of the B, C, and J elements 304, 312, and 314 defined as element contents. As a result, the compression rate can be increased compared to the method of assigning tag codes to all elements.

Hereinafter, the DET-MOI of FIG. 6 will be described.

DET-MOI is a structure including Date Encoder Types (DET) and Multiple Occurrence Indicator (MOI).

For each element or attribute having character data, the DET indicates to which encoder the character data or attribute value of the element is encoded. DET is exemplarily illustrated in FIG. 11, and can be represented by using 4 bits.

The MOI represents the occurrence indicator of all element tags included in an element tag or an XPath of an attribute in an XML document.

The MOI allocates 1 bit in order for each element node between the start node (context node) and the last node (the corresponding element tag or attribute) of the XPath.

Specifically, each bit value of the MOI allocates “1” or “0” depending on whether an element tag corresponding to each bit is generated when decoding an element tag or attribute converted into a path code. In other words, if an element tag corresponding to a specific bit needs to be created, assign it to “1”. However, when not generating an element tag corresponding to a specific bit, assign it as "0".

Subsequently, the MOI serves as a flag for generating all element tags included in the XPath when decoding the encoded XML document. In this case, when the last node is an element tag in XPath, the corresponding element tag should always be generated. Therefore, without assigning 1 bit whose value is “1”, it processes as default “1” when decoding.

Hereinafter, the length of FIG. 6 is demonstrated.

The length indicates the length of data of an element tag and an attribute corresponding to a path code. Here, the length includes a path, a DET-MOI, a length, and all byte lengths of data corresponding to an element tag of a lower layer when the corresponding element tag is defined as element content. The length of the element tag having only text data indicates the length of text data. In addition, the length for an attribute also indicates the length of the attribute value.

12 is a diagram for describing an encoding rule according to length.

Referring to FIG. 12, when the length is 0x00 to 0x7f, the first bit value is expressed as “0” and the length is encoded as it is in 1 byte. Here, the first bit serves as a flag indicating whether the length is expressed by adding the next 1 byte.

However, if it exceeds 0x7f, encoding is performed using extended 2 bytes or 3 bytes. In this case, when extending to 2 bytes, set the value of the first bit of the first byte to “1” and set the value of the first bit of the second byte to “0”. Similarly, when extending to 3 bytes, set the value of the first bit of each of the first and second bytes to “1”, and set the value of the first bit of the last third byte to “0” to encode the length. do.

The data in FIG. 6 means actual data such as character data.

Meanwhile, the data structure used for encoding the XML document is not limited to the data structure of FIG. 6, and the XML document may be encoded with a data structure including a path, a MOI, a length, and a data field except for the DET.

Hereinafter, a method of encoding an XML document valid for a schema created in the XML Schema language will be described.

13 is a flowchart for explaining a method of encoding an XML document.

Referring to FIG. 13, the XML encoder receives an XML document (S200).

Subsequently, the XML encoder searches for an element tag or attribute having character data in the XML document (S201). The XPath of the retrieved element tag or attribute is extracted, and the extracted XPath is converted into a path code (S202 and S203).

Subsequently, in order to indicate MOI, which is the appearance information of all the element tags included in the XPath, the XML encoder allocates 1 bit in order for each element node between the start node and the last node of the XPath (S204).

Specifically, the XML encoder allocates “1” to each bit value when generating the element tag corresponding to the bit when decoding the element tag converted to the path code, and “0” when not generating the element tag. Are assigned (S205, S206, S207, and S208).

Iteratively assigns path codes for element tags or attributes with the following character data:

14 is a diagram for explaining a method of decoding an XML document.

Referring to FIG. 14, an XML decoder first receives an encoded XML document (S300).

Next, the XML decoder extracts a path code from the encoded XML document and retrieves XPaths corresponding to the extracted path codes (S301 and S302).

Subsequently, the XML decoder selectively restores the element tag or attribute included in the retrieved XPath according to MOI, which is the appearance information.

For each bit of the MOI, the XML decoder restores an element tag corresponding to the bit only when each bit value is "1" (S303 to S306). The XML decoder restores an element tag or attribute corresponding to the last node of the searched XPath (S307).

In this manner, the XML decoder completes decoding by repeatedly performing the last path code of the encoded XML document (S308).

Hereinafter, the decoding method using the MOI in the XML document decoding method will be described in detail.

FIG. 15 is a diagram exemplarily illustrating a MOI, which is appearance information of all elements included in an XPath of an element tag or an attribute in an XML document.

Referring to FIG. 15, the A element is a global element, and the B, E, G, and I elements are child elements of the A element, forming an overlapping structure.

The XPath of an I element with character data is "./B/E/G/I". A method of indicating the appearance information of all the element tags included in this XPath will be described.

First, 1 bit is allocated in order for each element node between the start node of XPath and the last element of I element. That is, 3 bits are allocated to represent appearance information about B, E and G element nodes. Each bit value is assigned a value of "1" when generating B, E, and G element tags during decoding, and "0" when not generating.

For example, in the “111” of the MOI value of the first I element tag, each bit means B, E, and G elements in order. And since each bit value is assigned to "1", during decoding, both B, E and G elements 402, 404, 406 are generated.

Subsequently, since each bit value is assigned to "0" in the MOI value "000" of the second I element tag, the B, E, and G elements are not generated during decoding. This shows that the first I element 408 and the second I element 410 are siblings.

A MOI value of the third I element tag is “001”, and only a G element 412 corresponding to a bit having a value of “1” is generated. The MOI of the fourth to sixth I element tags is used to decode in the manner described above.

The MOI value of the seventh I element tag is “011”, and the E and G elements 428 and 430 corresponding to the bit having the value “1” are generated. Finally, the MOI of the eighth I element tag is used to decode in the manner described above.

According to the method of encoding and decoding an XML document using a path code according to the present invention, the assignment of unnecessary path codes is reduced by allocating unique path information to each XPath of selected elements without allocating path codes to all elements. By increasing the compression rate can be increased.

The encoding and decoding method of an XML document using a path code according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal line, a wave guide, or the like, including a carrier wave for transmitting a signal designating a program command, a data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

1 shows an example of an XML document in a text format.

2 shows a basic structure of binary encoding of an XML document used in TPEG and EPG.

FIG. 3 is a diagram for describing a conventional tag code allocation method using FIG. 2 for the XML document shown in FIG. 1.

4 is a block diagram showing the configuration of an apparatus for encoding an XML document according to the present invention.

5 is a block diagram showing the configuration of an apparatus for decoding an XML document according to the present invention.

6 illustrates a data structure used when encoding an XML document according to the present invention.

7 is a flowchart for clarifying a path code allocation method.

8 shows an example of a schema created with XML Schema.

9 shows a graphical diagram of the definition of a schema.

FIG. 10 is a path code table showing a path code assigned to the XPath of the elements and attributes of FIG. 9.

11 is a diagram illustrating an example of DET.

12 is a diagram for describing an encoding rule according to length.

13 is a flowchart for explaining a method of encoding an XML document.

14 is a flowchart for explaining a method of decrypting an XML document.

FIG. 15 is a diagram exemplarily illustrating MOI, which is information on appearance of all element tags included in an XPath of an element tag or an attribute in an XML document.

Claims (15)

In the method of assigning path codes to elements and attributes defined in a schema written in the XML Schema language, Assigning a unique path code to each XPath of selected elements among all the elements defined in the schema; And Assigning a unique path code to each of the XPaths of all attributes defined in the schema; Path code assignment method in the schema including. The method of claim 1, Assigning a unique path code to each of the XPaths of the some elements, Checking that all the elements are defined as global elements; And Assigning a unique path code to the XPath of the global element if defined as a global element Path code assignment method in the schema including. The method of claim 1, Assigning a unique path code to each of the XPaths of the some elements, For all of the elements, confirming that the element is defined as simple content having character data directly; If the elements are defined as simple content, assigning a unique path code to each of the XPaths of the elements Path code assignment method in the schema including. The method of claim 1, Assigning a unique path code to each of the XPaths of the some elements, For all of the elements, confirming that the element is defined recursively; And Assigning a unique path code to each XPath of the first element where the cycle begins and the second element where the cycle ends, if it is defined circularly Path code assignment method in the schema including. The method of claim 1, Assigning a unique path code to each of the XPaths of the some elements, For all the elements, confirming that the element is defined as mixed content; And Assigning a unique path code to the XPath of the element having mixed content, if defined as mixed content Path code assignment method in the schema including. In a method for encoding an XML document valid in a schema written in the XML Schema language, Retrieving all element tags and all attributes having character data directly in the XML document; Extracting an XPath of the retrieved element tag or attribute; And Converting each of the extracted XPaths into a preset path code by a path code allocation method using XPaths of elements and attributes; Encoding method of the XML document comprising a. The method of claim 6, Path code allocation method using the XPath of the element and attribute, Assigning a unique path code to each XPath of selected elements among all the elements defined in the schema; And Assigning a unique path code to each of the XPaths of all attributes defined in the schema; Encoding method of the XML document comprising a. The method of claim 6, Generating occurrence indicators of all the element tags included in the XPath, for an XPath of the element tag or attribute converted into a path code; Encoding method of the XML document further comprising. The method of claim 8, Generating the appearance information, Allocating 1 bit in order for each element node located between the start node and the last node of the XPath Encoding method of the XML document comprising a. 10. The method of claim 9, The step of assigning each bit value, When decrypting the element tag converted to a path code, Allocating “1” when the element tag corresponding to the bit is to be generated, and assigning “0” when the element tag is not generated. Encoding method of the XML document comprising a. In the method for decoding an XML document encoded based on a path code, Extracting a path code from the encoded XML document; Searching for an XPath corresponding to each of the extracted path codes from a path code table preset by a path code allocation method using an XPath of an element and an attribute; And Selectively restoring the element tag or the attribute according to the appearance information of the element tags included in the searched XPath XML document decoding method comprising a. The method of claim 11, Selectively restoring the element tag or attribute, Restoring an element tag corresponding to the bit only when the value of each bit is “1” for each bit of the appearance information; XML document decoding method comprising a. The method of claim 11, Selectively restoring the element tag or attribute, Restoring an element tag or attribute corresponding to the last node of the retrieved XPath Decoding method of the XML document further comprising. An apparatus for encoding a valid XML document into a schema written in the XML Schema language, A path code allocator for allocating path codes to elements and attributes defined in the schema by a path code allocation method using XPath of the elements and attributes to generate a path code table; And An XML encoder for retrieving all element tags and all attributes directly having character data in the XML document, and converting and encoding the XPaths of the retrieved element tags and attributes into the path codes defined in the path code table. Encoding apparatus comprising a. An apparatus for decoding an XML document encoded based on a path code, Extracts a path code from the encoded XML document, retrieves an XPath corresponding to the extracted path code from a path code table set by a path code allocation method using an XPath of an element and an attribute, and includes the path code in the searched XPath. A decoder configured to selectively restore the element tag or the attribute according to the appearance information of the extracted element tags to generate an instance tree; And XML document generator for generating an XML document from the generated instance tree Decoding apparatus comprising a.

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