JP2002007438A - Data managing method, its device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data managing device capable of retrieving data at high speed from the data at a point of time where the contents of data constituted of plural items stored in time series is changed. SOLUTION: A main control part 1 receives a retrieval request accepted by an input device 3 via an input/output control part 6. The main control part 1 specifies a record to be retrieved by reading a synthetic change bit from a synthetic index file 24 of an item to be retrieved according to a position where retrieval is started and the retrieving direction, Information corresponding to the specified record is read from the data file 21 and notified to an operator by a display device 4 or an output device 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention searches for data having a predetermined order, such as data at the time of change, at a high speed when managing data whose contents change over time. For improved data management techniques.

[0002]

2. Description of the Related Art In the past, it has become common in companies and the like to manage data of all employees using a data management device constituted by a computer. Such employee data includes, for example, a record group of items such as an employee's name, gender, date of birth, place of assignment, and position. For each record, the time (month / day) , The contents of which are usually changed. Causes of the change include address change, relocation in the workplace, and promotion.

As described above, when the contents of a record change, the old contents are not simply rewritten to the new contents, but the new contents are sequentially added to the previous contents. It is preferable to be able to acquire the record at the time point. For this reason, the storage location of the record is determined in the order of elapse of time, the data is stored as needed, and the relevant data is retrieved from the storage location as needed. Further, when managing employee data, there is a case where it is desired to check whether data regarding a specific item of the specific employee data has been changed. In this case, the presence / absence of data change is determined by comparison processing with data stored adjacently in a normal time series. In this determination processing, when there is a large amount of employee data or when the number of records included in the individual employee data is large, the readout time required for the search becomes long.

[0004] For this reason, the applicant of the present application has applied a patent as a management method for storing and managing such various kinds of data having a temporal order and providing a logical data structure stored in response to a user's request. No. 3016230 has been proposed. This enables high-speed retrieval of data at the time when the contents are changed from a plurality of data accumulated in time series, and the contents of data items accumulated according to the order are compared with the previous values. It is made searchable by using a change index using a "change bit" which is a minimum information unit indicating a difference from a new value.

[0005]

In the data management method described above, the "change bit" needs to be determined by comparing values before and after the data. For example, when managing employee data, an address, which is an item of specific employee data, may be composed of a plurality of items.
For example, if the contents are divided into address 1, address 2 and address 3, where address 1 classifies the name of the prefecture, address 2 the name of the city, town and village, and address 3 the address, and so on. In order to know whether or not the address has been changed, it is necessary to compare each of the address 1, the address 2, and the address 3 and determine whether any of them has changed. That is, to make this determination,
The “change bit” for address 1, the “change bit” for address 2, and the “change bit” for address 3 must each be read from the storage device and determined, and it takes time to read and unnecessary time for search processing. There was a problem that becomes longer.

Accordingly, the present invention provides a method for performing a plurality of "changes" when it is necessary to comprehensively determine the change status of a plurality of items to determine whether or not there is a change from data stored in accordance with an order such as a time series. A main object of the present invention is to provide a data management method that simplifies the process of reading and judging “bits” from a storage device and enables high-speed search for the presence or absence of data change. Another object of the present invention is to provide a data management device that enables quick and efficient data management to which this management method is applied. Another object of the present invention is to provide a recording medium suitable for executing this management method on a general-purpose computer device.

[0007]

A data management method according to the present invention for solving the above-mentioned problems is a method for recording and reading a plurality of types of data in accordance with a predetermined order. The input data is compared with the data recorded in the immediately preceding stage for each item, and the change bit of a different value is retained for each item according to the input data depending on whether the comparison result is the same or different. A recording step of storing a composite change bit, which is the result of the logical conditional expression between the change bits of the item, in a file in accordance with the order in which the data is input; and A computer device for executing a search step of specifying a time point and searching for the data at the specified time point as data whose contents have been changed. A.

In the retrieval step, if the combined change bits have the same value, the combined change bits are skipped until the value of each combined change bit changes in a predetermined search direction, It is also possible to include reading each time and detecting whether or not the value has changed. In the recording step, the composite change bit may be held in association with time information.

According to another aspect of the present invention, there is provided a data management apparatus comprising: a data file for recording a plurality of types of data according to a predetermined order in a record unit including one or more items; An index file associated with the record items recorded in the file,
A combined item table for recording a logical conditional expression between items of the index file, a combined index file associated with items of records recorded in the combined item table, the data file and the index file, Recording control means for performing recording control on the composite item table and the composite index file. The recording control means, when triggered by a data recording request for a specific item, creates a new record including data related to the recording request. Means for creating and recording in the data file, and means for recording in the index file a change bit indicating whether or not the data of the specific item has changed in accordance with the order, and Operation result of logical conditional expression between items recorded in composite item table It is one that is configured to record in the synthesis index file.

[0010] Another data management apparatus of the present invention includes a data file in which data conforming to a predetermined order is recorded in a record unit composed of two or more items, and a data item recorded in the data file. An index file which is associated with and records a change bit indicating whether or not the data of the item is changed according to the order, and a composite item table for recording a logical conditional expression between the items of the index file And a composite index file that is associated with an item of a record recorded in the composite item table and records a composite change bit representing a result of a logical conditional expression operation between the items of the index file. Reads the index file and the record information of the composite item table and composite item index. And a read control means for controlling,
In response to a search request for a record in which data of a combined item in which a specific item is composed of a plurality of items has been changed, a record including the corresponding data based on the combined change bit in the combined index file corresponding to the combined item Is configured to be specified.

Each of the above data management devices is preferably
The information processing apparatus further includes means for associating the identification information of the record recorded in the data file with the time information, and the record is specified based on the time information.

According to another aspect of the present invention, there is provided a recording medium on which is recorded a program code for causing a computer to execute the following processing in a method for recording and reading a plurality of types of data in a predetermined order. Also, it is a computer-readable recording medium. 1) Each time the data is input, the input data is compared with the data recorded in the immediately preceding stage for each item, and different values are obtained depending on whether the comparison result is the same or different. A process of holding a change bit for each item according to the input data. 2) A process of storing a composite change bit, which is an operation result of a logical conditional expression between the change bits of the item, in a file according to the order in which data is input. 3) a process of referring to the file to identify a point in time at which the composite change bit has changed, and searching for the data at the point in time as data whose contents have been changed;

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the data management device will be described below. FIG. 1 is a hardware configuration diagram of the data management device. This data management device has a main control unit (CPU1: Central Pro
processing unit) 1, a storage device 2 connected to the CPU 1, an input device 3 for receiving a request from an operator, a display device 4 for displaying input / output data, and It comprises an output device 5 for outputting to the outside of the data management device, and an input / output control unit 6 for controlling input / output of data between the CPU 1, the input device 3, the display device 4 and the output device 5.

The CPU 1 executes necessary control or processing by reading a control program or an application program. The storage device 2 is a fixed storage device including a magnetic storage device such as a hard disk and a semiconductor storage device such as a RAM, and stores various files and program codes. In this embodiment, a data file 21, an index file 22, a combined item table 23, a combined index file 24, a storage / search program 25, a control program, and the like are stored. These data files 21 and the like are stored in the fixed storage device, for example, a flexible disk, an optical disk,
In some cases, the data may be recorded on a portable recording medium such as a magneto-optical disk, CD-ROM, CD-R, DVD, or magnetic tape in a form readable by the CPU 1. In some cases, another device installs the storage device 2 via a communication unit (not shown). The data file 21, index file 22, composite item table 23, and composite index file 24 will be described later.

The recording / retrieval program 25 is for forming a data recording module for performing data recording processing and a data retrieval module for performing data retrieval processing.

The control program performs a part of the actual processing based on the instruction of the recording / retrieval program 25. When the module is formed through the processing, or when the module is formed in cooperation with another application. However, here, for convenience, the description will be made assuming that the above-described module is formed only by the recording / retrieval program 25.

The input device 3 is data input means such as a keyboard and a mouse. A data recording request and a data search element are received from the operator. The display device 4 has a CR
T (Cathode Ray Tube) or FPD (Flat Panel Dis
play), and displays the content of a search request from the operator and the processing result according to the search request. Output device 5
Is constituted by a printer or the like, and outputs a processing result to the outside by printing or the like. The input / output control unit 6 transmits the request received by the input device 3 to the CPU 1 and displays the request on the display device 4, and sends a processing result to the display device 4 or the output device 5 according to the request received by the input device 3. .

Next, the data file 21, index file 22, composite item table 23, and composite index file 24 used in this embodiment will be described. <Data File> FIG. 2 is a diagram showing an example of the contents of the data file 21. The data file 21 is a file provided for storing various data generated in accordance with the order, and various data is recorded in units of records. Each record is configured by data corresponding to a predetermined item. In the example of FIG. 2, for example, the record of record number # 3 is the item a
Da3 corresponding to item b, data Db corresponding to item b
3, Dc3 corresponding to item c, and data Dd3 corresponding to item d.

Data relating to at least one of the items a to d as shown in the figure is stored in a predetermined order. Examples of the order include a time-series order such as an old order or a new order. Examples of data stored according to such a time series include employee data described in [Prior Art] above. That is, new records are sequentially created with the data update, and n records are accumulated in the data file 21 from record number # 1 to record number n.

<Index File> FIG. 3 is a diagram showing an example of the contents of the index file 22. The index file 22 is a file provided for recording and retrieving a change point of data stored according to the order of the data file 21. The index file 22 shown in FIG. 3 is provided corresponding to the item b of the data file 21 of FIG. Change bits Bb1 to Bb1 indicating whether or not newly recorded data is different from data recorded immediately before based on the order.
Bbn is recorded for each record. This change bit is
It is sufficient to indicate only the presence or absence of a change point in the order of each item of data of the corresponding item, so it is sufficient if there is at least one bit of data. For example, in the change bit Bb3 corresponding to the record number # 3, the data Db3 corresponding to the item b included in the record of the record number # 3 is different from the data Db2 corresponding to the item b included in the record of the record number # 2. If it is, "1" is set, and if it is the same, "0" is set. However, since the record of record number # 1 is the first record in the data file 21, "1" is set as a default value.

As described above, the index file 22
Is provided for each item. For example, when data on items b and c is stored in accordance with the above-described order, separate index files are provided for items b and c.

<Synthesis Item Table> FIG. 4 is a diagram showing an example of the contents of the synthesis item table 23. The composite item table 23 is a collection of a plurality of data items that form a pair with a composite item name and a logical operation expression indicating the substance of the item.
The logical operation expression is composed of a logical operator between the composite item name and the items (items a to d in the example of FIG. 2) shown in the data file 21, that is, a logical sum, a logical product, a logical difference, a logical negation, and the like. This is a logical algebraic expression. In addition, a change bit of each item is used as an operation element, and a change bit obtained by such a logical operation expression is called a composite change bit. In the example of FIG. 4, for example, it is shown that the composite item x is configured by the logical sum of the item b, the item c, and the item d.

<Synthesized Index File> FIG. 5 is a diagram showing an example of the contents of the synthesized index file 24. The composite index file 24 is a file provided for recording and searching for a change point of a composite item of data stored in the data file 21 according to the order. The composite index file 24 shown in FIG.
This is an example provided for the composite item x of the item condition table 23 in FIG. 4, and is a result of performing a logical operation (in this example, a logical sum is performed) on the changed bits of the items b, c, and d. The composite change bit is recorded for each record according to a predetermined order. That is, the composite change bit is the item b
If any of the change bits of item b, item c, or item d of item d is “1”, it becomes “1”, and if all the change bits are “0”, it shows “0”. Will be.

<Data Recording> Next, data recording processing in this embodiment will be described with reference to FIG. This processing is executed by the data recording module described above.
When data from the operator is input through the input device 3, the input data is sent to the data recording module via the input / output control unit 6 (step 1). The data recording module determines whether a data file 21 for the input data exists in the storage device 2 (Step S2). For example, if the input data is data relating to a predetermined employee, it is determined whether a data file corresponding to the employee exists.
If the corresponding data file 21 exists (step S2: Yes), a new record to be recorded in the data file 21 is created (step 3).
The newly created record will contain the entered data, except for the fields that correspond to the entered data,
The record recorded immediately before is used as it is. For such a record, a number obtained by adding “1” to the record number of the immediately preceding record is added as a new record number, and this is recorded in the data file 21 as the latest record at that time.

Thereafter, it is determined whether or not the index file 22 for each item of the data file exists in the recording device 21 (step S4). If the index file 22 exists (step S4: Ye
s) For the item corresponding to the index file 22, the data recorded in step S3 is compared with the data recorded immediately before, and if each data is different, it is "1" and the data is the same. In some cases, "0" is recorded as a new change bit in association with the record number newly assigned in step S3 (step S3).
5).

There may be a plurality of index files 22 for different items. In this case, data is compared for each item. After recording the change bit, the process proceeds to the processing of the composite change index (step S10). If the data file 21 corresponding to the input data does not exist in step S2 (step S2).
2: No), a new data file for recording the input data is created (step S6). The creation of the new data file may be performed by notifying the operator that the corresponding data file does not exist in the storage device 2 and prompting the operator to input a data file creation instruction. New data file 21
Is created, a record containing the entered data is created, and this is the first record in the data file 2
1 is recorded. In this case, since this is the first record, "1" is added to the record number (step S).
7).

Next, it is determined whether an index file 22 needs to be created for each item of the record (step S8). In this determination process, when creating a record in step 7, the operator is prompted to input an instruction, and after the record is recorded in accordance with the input instruction, the operator sequentially checks whether or not an index file is created for each item. You may do it.

In the created one or a plurality of index files 22, a change bit "1" which is a default value corresponding to the record number # 1 is recorded. (Step S9). After recording the change bit, the process proceeds to the process of the composite change index (step S10). Data file 2
Index file 22 for any of the items 1
If it is not necessary to provide (step S8: No), the process proceeds to the process of the composite change index (step S10).

After the processing of step S5 is completed, step S5
4: No, after completion of step S9 and step S8:
Next to No, it is determined whether or not a composite item name exists in the composite item table 23 (step S10). If the combination item name exists in the combination item table 23 (step S10: Yes), the combination change bit is calculated according to the definition of the logical expression corresponding to the combination item name, and the combination associated with the combination item name is calculated. Record in the index file 24 in association with the corresponding record number (step S1).
1).

In the operation of the composite change bit, a change bit for each item appearing in the logical expression is specified, and the change bit is logically operated. The change bit for each item is specified from the corresponding record number of the index file 22 when the index file 22 exists. If there is no index file, the above steps S2
A temporary change bit is obtained in the same procedure as in the processing of S9. Since there may be a plurality of composite item names, a composite change bit is obtained for each item and recorded in the corresponding composite index. After recording the composite change bit, the data recording process ends.

If the composite item name does not exist in the composite item table (step 10: No), the data recording process ends. By the above operation, the data recording process is executed, and the recording of the change bit in the index file 22 and the recording of the composite change bit in the composite index file 24 are performed as necessary.

<Search of Data> Next, a search process of changed data (record) will be described. The flow of the search process will be described with reference to FIGS. Assuming C
It is assumed that the recording / search program 25 is executed by the PU 1 to form a data search module. When a search request from the operator is received by the input device 3, the search request is sent to an area readable by the data search module via the input / output control unit 6 (step S21). The search request from the operator includes a data file to be searched, a combination item, search target data, a position (time) at which to start the search, a search direction, and the like. Specify the search range as needed.

After the search request is accepted, the data search module starts the search with the record number #m based on the search start position specified by the operator.
Is specified (step S22). When the record number #m is specified, reading of the synthesis change bit of the synthesis index file 24 corresponding to the synthesis item accepted in step S21 is performed. Here, record number #
From the composite change bits corresponding to m, n predetermined composite change bits are read in accordance with the search direction specified by the operator (step S23).

The data search module also checks whether the composite change bit corresponding to the record number #m is "1" out of the read n composite change bits (step S24). If the composite change bit is “1” (step S24: Yes), this record number #m
Is notified to the operator as a search result, and the search process is terminated (step S25).

If the composite change bit corresponding to the record number #m is not "1" (step S24: N
o), It is checked whether the search direction specified by the operator is in ascending order or not (step S26).
If the search direction is ascending (step S26: Ye
s) It is checked whether the record number #m is the minimum record number (step S27). If the record number #m is not the smallest (step S27: No), 1 is subtracted from the record number #m, and the composite change bit corresponding to the subtracted record number is referred to (step S28).

On the other hand, if the search direction is not the ascending order in step 26 (step S26: No), it is checked whether the record number #m is the maximum record number (step S26).
30). If the record number #m is not the maximum record number (step S30: No), 1 is added to the record number #m.
, And refers to the composite change bit corresponding to the record number after the addition (step S31).

In step S27, record number #
If m is the minimum (step S27: Yes), the operator is notified that the corresponding record has not been detected, and the search process ends (step S32).

After the processing in step S28 and in step S28
After the process of step 31, it is determined whether or not the composite change bit corresponding to the record number #m has been read (step S29).
If it has been read (step S29: Yes),
Returning again to the processing of step S24, it is determined whether or not the composite change bit is "1". If the composite change bit has not been read (step S29: No),
Returning again to the processing of step S23, the n composite change bits are read. By such processing, a record requested by the operator can be quickly searched.

<Specific Example of Data Retrieval> Next, a specific example of data retrieval using the data file 21 illustrated in FIG. 9, the composite item table 23 illustrated in FIG. 10, and the composite index file 24 illustrated in FIG. Will be described. In the illustrated data file 21, various data relating to the employee A are recorded, and in the composite item table 23, a composite that refers to the items “address 1”, “address 2”, and “address 3” in the data file 21. Item "address" is defined. Also, the composite index file 24 is
This is provided corresponding to the combination item “address” in the data file 21.

Here, a case will be described in which the search request is a request for searching for a record when an address change has occurred in the data file of employee A. However, it is assumed that the operator has designated a point in time when the search is to be started, and the record number corresponding to this point is 12.
Further, it is assumed that the number n of combined change bits read from the combined index file 24 is “3”.

The data management device accepts the request from the operator and sets the record number #m for starting the search to "1".
2 ”(steps S21 and S22). In this example, since the search direction is in ascending order, three combined change bits are read in ascending order from record number # 12 (step S2).
3). This bit string becomes "010" as is clear from FIG. When the composite change bit is read,
It is determined whether the composite change bit corresponding to the record number # 12, that is, the first bit of the bit string is "1" (step S24). Since the bit corresponding to record number # 12 is "0", the search direction is determined next (step S26). Since the search direction is in ascending order and the record number #m is not the minimum, the record number #m is decremented by "1" to become "11" (steps S27 and S27).
28). Thereafter, after step S29, step S24
And the determination of the composite change bit is performed again.

In this example, in step S24, it is determined that the composite change bit corresponding to record number # 11 is "1", and information corresponding to this record number "11" is notified to the operator (step S24). S2
5).

<Detection of Number of Changes> The data management apparatus of the present embodiment can also detect the number of times data has been updated. The operation in this case will be described. Here, it is assumed that a data search module is formed. When the operator requests acquisition of the number of changes for a specific composite item in the data file 21, a composite index file corresponding to the specified composite item is specified from the composite item table 23, and , All recorded composite change bits are read out.

Thereafter, the sum of all the read combined change bits is obtained. The determined result is notified to the operator. For example, in the case of the composite index 24 shown in FIG. 11, "4" is notified to the operator. This number represents the address where employee A has lived. The value obtained by subtracting “1” from this number is the number of moves.

As described above, in the present embodiment, the information is recorded in the composite index file 24 in the process of searching for information at the time of data change and the process of obtaining the number of times of data change based on a condition composed of a plurality of items. Only reading the composite change bit eliminates the need to read the data recorded in the data file 21 on a record-by-record basis and compare it. Further, it is not necessary to perform a logical operation process corresponding to a condition between a plurality of items at the time of executing a search, and the process is simplified in this respect as well.

In this embodiment, the combination item table 23 is specified when a search request is made. However, the search request may be made in the form of a search formula between a plurality of items.
The processing module analyzes the search formula, determines the combination of the item and the condition, and selects and processes the optimum one from the composite indexes prepared at the time of data registration. It should be noted that not only the original item of the record but also other synthesized items can be used in the logical operation expression constituting the synthesized item.

[0047]

As is apparent from the above description, according to the present invention, in a data management apparatus for managing data stored in chronological order, a predetermined item is composed of a plurality of items. Based on the conditions, the information retrieval process at the time of data change can be simplified and can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a data management device according to an embodiment of the present invention.

FIG. 2 is a configuration example of a data file stored in a recording device of the data management device.

FIG. 3 is a configuration example of an index file stored in a recording device of the data management device.

FIG. 4 is a configuration example of a composite item table stored in a recording device of the data management device.

FIG. 5 is a configuration example of a composite index file stored in a recording device of the data management device.

FIG. 6 is an explanatory diagram showing a procedure of a data recording process according to the embodiment.

FIG. 7 is an explanatory diagram showing a procedure of a change point search process according to the embodiment;

FIG. 8 is a procedure explanatory diagram showing a procedure of a change point search process in the embodiment.

FIG. 9 is an example of a data file stored in the data management device.

FIG. 10 is an example of a composite item table stored in the data management device.

FIG. 11 is an example of a combined index file stored in the data management device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Main control unit (CPU) 2 Storage device 3 Input device 4 Display device 5 Output device 6 Input / output control unit 21 Data file 22 Index file 23 Synthetic item table 24 Synthetic index file 25 Recording / retrieval program

Claims (8)

[Claims] 1. A method for recording and reading a plurality of types of data according to a predetermined order, wherein each time the data is input, the input data and the data recorded immediately before are input for each item. In comparison with the comparison result, when the comparison result is the same and when the comparison result is different, a change bit having a different value is held for each item according to the input data, and the calculation result of the logical conditional expression between the change bits of the item is held. A recording step of holding a certain combined change bit in a file in accordance with the order in which the data is input; specifying a time point at which the combined change bit is changed with reference to the file; A computer device for executing a search step of searching for the data as searched data. 2. In the search step, when the combined change bits have the same value, the combined change bits are skipped until the value of each combined change bit changes in a predetermined search direction. The data management method according to claim 1. 3. The data management method according to claim 1, wherein said retrieving step includes a step of reading said composite change bit by a predetermined number and detecting whether or not the value has changed. 4. The data management method according to claim 1, wherein said recording step holds the combined change bit in association with time information. 5. A data file for recording a plurality of types of data according to a predetermined order in a record unit composed of one or more items, and a data file associated with a record item recorded in the data file. An index file, a composite item table for recording a logical conditional expression between the items of the index file, a composite index file associated with the items of the records recorded in the composite item table, An index file, and recording control means for performing recording control on the composite item table and the composite index file. The recording control means, when triggered by a data recording request for a specific item, stores data relating to the recording request. To create a new record including Means for recording, in the index file, a change bit indicating whether or not the data of the specific item has changed in accordance with the order, between the items recorded in the composite item table in response to the data recording request. A data management device characterized by being configured to record an operation result of a logical conditional expression in the composite index file. 6. A data file in which data conforming to a predetermined order is recorded in a record unit composed of two or more items, and a data file associated with an item of a record recorded in the data file. An index file which records a change bit indicating whether or not the data changes according to the order, a composite item table for recording a logical conditional expression between items of the index file, and a composite item table. A composite index file that is recorded with composite change bits that are associated with the items of the record to be processed and that represent the results of the logical conditional expressions between the items of the index file; the data file and the index file; and the composite item table Reading control means for controlling reading of the record information of the composite item index; In response to a search request for a record in which data of a composite item in which a specific item is composed of a plurality of items has been changed, the corresponding data is determined based on a composite change bit in a composite index file corresponding to the composite item. A data management device characterized in that it is configured to identify a record including 7. A system further comprising means for associating identification information of a record recorded in said data file with time information, and wherein a corresponding record is specified based on said time information. The data management device according to claim 4 or 5, wherein 8. A computer-readable recording medium in which a program code for causing a computer device to execute the following processing in a method of recording and reading a plurality of types of data according to a predetermined order is recorded. 1) Each time the data is input, the input data is compared with the data recorded in the immediately preceding stage for each item, and different values are obtained depending on whether the comparison result is the same or different. A process of holding a change bit for each item according to the input data. 2) A process of storing a composite change bit, which is an operation result of a logical conditional expression between the change bits of the item, in a file according to the order in which data is input. 3) a process of referring to the file to identify a point in time at which the composite change bit has changed, and searching for the data at the point in time as data whose contents have been changed;