JP2002324069A - Data management apparatus and map display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow processing map data and the like at high speed. SOLUTION: A map server 10 has a map database 11 in which much of mesh data is registered. The database 11 is constituted as a layered file system in which each name of directory and file is composed of a minimum number of letters. A storing position when caching is pre-decided with dividing a mesh number based on the position coordinates by a size of a cache area 35 and acquiring the rest. When searching cache data, the position in the area 35 is acquired from the number of a desired file to directly detect data at the position. If unnecessary data is stored, the data is deleted to release the storage area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data management device and a map display system.

[0002]

2. Description of the Related Art In a computer system, a CPU
The (Central Processing Unit) retrieves data stored in a memory such as a RAM (Random Access Memory) based on a program, and performs predetermined arithmetic processing.

When the required data size is smaller than the memory size, all the required data can be stored in the memory and processed. However, when the amount of data handled by the program exceeds the memory size, all necessary data cannot be stored in the memory in advance.

Therefore, data is stored in a large-capacity external storage device such as a hard disk drive (HDD), and necessary data is transferred to a memory for processing. However, the data writing speed and the reading speed of the external storage device are generally slow, and it takes time to search for specific data from a large amount of data. Therefore, when frequent data exchange is performed between the external storage device and the memory, the execution speed of the program is reduced.

For this reason, a cache system is adopted,
The data once read by the memory is temporarily stored in a memory area called a cache memory. As a result, when the cached data is used again, it is only necessary to search the cache memory and read out the desired data, thereby improving the execution speed of the program. In order to use the cache memory efficiently, unnecessary data is deleted from the cache memory by a memory release program called a garbage collector.

What is left in the cache memory and what is deleted is an important issue. When the desired data cannot be obtained by searching the cache memory (cache miss)
Must search the mass storage device for the data. Further, if the unnecessary data is stored in the cache memory forever, a memory area for temporarily storing new data becomes insufficient.

For this reason, in the prior art, a cache management table is prepared for managing data stored in the cache memory. In this management table, a priority based on the number of data references and the like is set for each data stored in the cache memory. By searching the cache management table, desired data can be read. Garbage collection can be performed by referring to the cache management table and deleting low priority data.

[0008]

As described above, the use of the cache memory eliminates the need to access the large-capacity storage device for data retrieval every time data is read, thereby increasing the processing speed of the program. it can.
However, in order to use the cache memory, it is necessary to create a cache management table and update the table contents. In addition, when the garbage collector that deletes unnecessary data is executed in the background, the load on the CPU increases correspondingly, and the overall program execution speed decreases.

A case where such management of the cache memory has a great effect on the execution speed of the program is as follows.
This corresponds to a case where a program that requires new data as needed while using existing data in the cache memory is executed. A typical example is a map display system.

In the map display system, the map is frequently scrolled, enlarged or reduced in accordance with the operation of the user. When scrolling or enlarging / reducing, the map data used for the current display and the map data that needs to be newly read (although it differs depending on the scroll width, enlargement ratio, reduction ratio, etc.) are simultaneously or continuously displayed. Sometimes used. In the map, adjacent geographic elements (for example, individual geographical objects such as roads, railway tracks, rivers, buildings, premises, feature names, map symbols, icons, etc.)
Are related to each other, and scrolling or the like is often performed while reusing already displayed data. Further, the map display system uses a large amount of data, although it differs depending on the range covered, the scale, and the like. Therefore, it is important to quickly search for data necessary for display from a large amount of data, delete unnecessary data, and use the cache memory efficiently.

By the way, in the conventional map display system,
When a client requests map data from a map server, desired map data is specified by latitude and longitude, and the latitude and longitude are passed to the map server as a character string. Upon receiving the data request, the map server newly generates mesh data in the range specified by the latitude and longitude, and returns it to the client.

That is, for each data request, the client needs to transmit information of about several tens to one hundred characters to the map server. Therefore, for example, when transmitting and receiving map data using a communication network with a narrow data band such as the Internet, even if only a data request is made, the load on the data band increases, and the map data can be received smoothly. Difficult to do. In addition, the map server side generates a new mesh data in a specified range by interpreting the character string of the latitude and longitude, so that the response is low and a smooth map display is more difficult.

The present invention has been made in view of the various problems described above, and an object of the present invention is to provide a data management device and a map display system capable of performing data processing at high speed. Another object of the present invention is to provide a map display system that enables continuous and smooth map operations by high-speed data processing. Further objects of the present invention will become clear from the embodiments described later.

[0014]

Means for Solving the Problems In order to solve the above problems,
The data management device according to the present invention is a second storage device having a second storage space smaller than the first storage space from the first storage device holding a large number of data in the n-dimensional first storage space. The data is managed by transferring predetermined data to the storage device, and is provided with a storage position designation unit, a data acquisition unit, and a data deletion unit. The storage position designating means presets a designated storage position in the second storage space for each of a large number of data held in the first storage space. The data acquisition means retrieves predetermined data from the first storage space and stores the retrieved data in a designated storage location set for the data. The data deleting means, if the predetermined data is not stored in the designated storage location,
The data already stored in the designated storage location is deleted.

In the first storage device, for example, an n-dimensional first storage space such as a two-dimensional array or a three-dimensional array is formed, and data is stored in the first storage space. An n-dimensional second storage space smaller than the first storage space is formed in the second storage device. For each data stored in the first storage space, a storage position in the second storage space is set in advance as a designated storage position. Data retrieved and read from the first storage space is stored in the second storage space at the designated storage location. Therefore, when searching for data, it is not necessary to search the entire second storage space, but it is sufficient to directly search the designated storage location assigned to the desired data. However, since the second storage space is set smaller than the first storage space, a plurality of data are allocated to one designated storage location. How much data is allocated to each designated storage location is determined by the size of each storage space. Simply, (size of first storage space / second
Data size is allocated to one designated storage location. Therefore, when the data at the designated storage location is searched, the desired data may not be stored at the designated storage location, and other data sharing the designated storage location may be stored. In this case, the data deletion means deletes the data already stored at the designated storage location and releases its memory area.

As described above, when data is transferred from the first storage space to the second storage space, the data is stored in a predetermined storage location (data cache), which facilitates retrieval. If the desired data is not stored in the designated storage location, the second storage space is efficiently used to delete unnecessary data stored in the designated storage location (garbage collection). Can be.

Here, each coordinate value in the first storage space is stored in the second storage space.
Each designated storage position can be set by assigning in advance to each coordinate value of the storage space. Specifically, it is preferable to uniformly assign each coordinate value of the first storage space to each coordinate value of the second storage space.

Although it is possible to determine the designated storage location based on data-dependent properties such as the type of data and the frequency of use, the structure for allocating storage locations is complicated. Therefore,
By associating the coordinate values of the first and second storage spaces with each other, the designated storage position is determined without depending on the properties of the data.

As a method of uniformly assigning each coordinate value of the first storage space to each coordinate value of the second storage space, for example, a continuous integer value is assigned to each coordinate value of the first storage space. Each of these coordinate values may be divided by the size of the second storage space to obtain a remainder, and the coordinate value in the second storage space indicated by the remainder may be set as the designated storage position.

Specific examples will be described. For convenience of explanation, the first storage space is a 10 × 10 two-dimensional array, and the second storage space is a 3 × 3 two-dimensional array. The first storage space is X
Continuous integer values of 0 to 9 on the axis and the Y axis, respectively,
Are continuously given integer values of 0 to 2 on the x-axis and the y-axis of the storage space. The remainder is obtained by dividing the coordinate value (X, Y) of the first storage space by the size of the second storage space (both are 3 in the x and y axis directions). The remaining value is any one of 0, 1, and 2. For example, the data stored at the coordinate value (0, 0) in the first storage space is:
Stored in the second storage space at the coordinate value (0, 0);
The data stored at the coordinate value (7, 9) in the first storage space is stored at the coordinate value (1, 0) in the second storage space. That is, the remainder ((X mod Cx), (Y mod) when the coordinate value (X, Y) of the first storage space is divided by the size (Cx, Cy) of the second storage space.
Cy)) is the designated storage position. Therefore, when reading data from the second storage space, it is sufficient to know only the coordinate values of the desired data in the first storage space. This is because the storage location in the second storage space is predetermined according to the original storage location of the data.

Therefore, by storing data that can be used continuously in the n-dimensional space in the first storage space with coordinate values of integer values determined according to positions in the n-dimensional space, the efficiency can be further improved. Data can be cached and searched for more easily.

Here, "data that can be used continuously in the n-dimensional space" is, for example, data that is developed in the n-dimensional space in a relationship with each other, and adjacent data can be used continuously. A typical example is map data. It should be noted that this is different from data that is simply read sequentially.

By specifying desired data with coordinate values set based on the position in the n-dimensional space, a designated storage position of the data is immediately obtained, and whether the data is stored in the second storage space is determined. Can be checked.

In the map display system according to the present invention, a map server having whole map data subdivided into a large number of fragment map data, a desired fragment map data is received from the map server via a communication network, and the received fragment map data is received. A client for drawing and displaying a map image from the map data. Further, in the present map display system, the client is provided with a cache data management device for storing fragmentary map data received from the map server in a cache memory having a storage space smaller than the storage space of the map server.

The cache data management device includes a coordinate allocating unit, a data obtaining unit, and a data deleting unit. The coordinate assigning means assigns each coordinate value in the storage space of the map server to a coordinate value in the storage space of the cache memory. The data acquisition means retrieves predetermined data from the map server, and stores the retrieved data in the cache memory with coordinate values assigned to the data. If the predetermined data is not stored in the cache memory at the assigned coordinate value, the data deletion means deletes the data already stored at the coordinate value from the cache memory.

Thus, the client can quickly read the data stored in the cache memory, draw a map, and display the map. That is, the client requests data of a range necessary for display from the map server,
The map data received from the map server is drawn and displayed. Since no drawing is performed in the map server, the processing load on the server side can be reduced. Therefore, even when a large number of clients request map data, the map server can transmit necessary map data to each client one after another.

The map data received from the map server is:
The data is stored in a storage space in the cache memory at a predetermined coordinate value. When the display range is changed by a scroll operation or the like, it can be reused by directly searching a predetermined position in the cache memory without searching the entire cache memory or referring to a separately prepared cache management table. Possible map data can be read out immediately. Map data that has become unnecessary because it has gone out of the display range is deleted by the data deletion means, and the memory area of the cache memory is released correspondingly. Since necessary data is stored in the cache memory at a predetermined position based on the coordinate value, it is possible to immediately know whether or not data necessary for display is cached, and it is possible to quickly delete unnecessary data. it can. The cache memory can be used efficiently without the trouble of generating and updating the cache management table.

Here, the fragment map data is, for example, individual geographical elements (for example, each road, each railway track, each river, each building, each site, each feature name, each map symbol, each map element included in the map image, This is data (for example, polygon data, line data, character data, bitmap image data, etc.) representing each geographical object such as each icon. Alternatively, the fragment map data may be, for example, map data of a small area (mesh) in which the entire area covered by the entire map data is locally subdivided by latitude and longitude.

On the other hand, the data management device according to the present invention includes a server for storing data and a client for obtaining data from the server. This is a so-called client-server system. The server has a hierarchical file system in which the names of directories and files are represented by the minimum number of characters. Identification information other than the file name is given to each file in advance. A conversion unit for converting the data into a path name in the file system based on the identification information given to the file of the desired data; a request unit for requesting the server to transmit desired data by the path name obtained by the conversion unit; It has.

Therefore, the data request from the client to the server is a path name composed of the name of the minimum character, and this simplest path name uniquely identifies an arbitrary file stored in the hierarchical file system. I do. Specifically, for example, HTTP (Hyper Text Transfe
r request), the client uses “http: // server name / a / b / c / 8 / 5.dat”
Send an HTTP request such as to the server. The server receiving this request specifies the file by the path name and returns this file to the client. The server simply returns the file identified by the path name.

Here, in the file system on the server side, a name having a minimum number of characters is set for each of a root directory name, a subdirectory name and a file name immediately below the root directory, and a file name in the subdirectory. The “minimum number of characters” refers to the OS (Operating
System) is a character (including numbers and symbols) that is permitted to be used, and it is the smallest unit of character.
For example, an alphabet or a number represented by 1 byte can be adopted as the name of the minimum number of characters. “Identification information” is information for distinguishing one file (data) from another file (data) in a group of files having the same purpose of use. As a whole file group, each file is given unique identification information.

A group of files having the same purpose of use includes, for example, a fragment map data group constituting the whole map.

That is, the map server stores a large number of fragmented map data, each of which has a file name with the minimum number of characters, in a hierarchical file system in which each directory name has the minimum number of characters. By converting the identification information given to each piece of fragmented map data based on the position in the space into a path name in the hierarchical file system composed of the minimum number of characters, desired data can be requested from the map server. As a result, the map server can promptly transmit the requested fragmentary map data, and a faster map display can be performed.

Further, a map display system can be configured by combining the above-described cache data management device and a hierarchical file system with a minimum number of characters.

As a result, data can be obtained and read out at a higher speed, and a continuous and smooth map display can be efficiently performed.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where an embodiment of the present invention is applied to a map display system will be described with reference to FIGS.

FIG. 1 is a configuration explanatory diagram schematically showing the overall configuration of the map display system according to the present embodiment.

The present map display system comprises a map server 10 for providing a map providing service and a plurality of client computers (only one is shown) 30 used by a user. 30 means, for example, the Internet 2
0 is communicably connected via a communication network such as 0.

The map server 10 has a map database 11 in which map data of a wide area is stored. The client computer 30 has a client program 31 for accessing the map server 10. The client program 31 includes a map display program 32 for requesting the map server 10 to transmit map data and for drawing and displaying the map data received from the map server 10, for example, plug-in software. Comes in a form like. The client computer 30 also includes, for example, a display device 33 such as a liquid crystal display and an operation device 34 such as a mouse. Further, the client computer 30 is configured as a computer system using a microcomputer, and has an arithmetic processing unit such as a CPU and a storage unit such as a memory. In the storage unit, a cache area 35 for temporarily storing map data acquired from the map server 10 is formed as described later with reference to FIG.

In the present embodiment (although this need not be the case), the map server 10 uses the WWW (World-Wid
e Web) a server and the client computer 30
Is a WWW browser. The map server 10 and the client program 31 make a request for map data (HTTP request), receive map data (HTTP response), and the like according to the HTTP protocol.

The map database 11 is, for example, an HDD
This is realized using a mass storage device such as a device. The map database 11 includes, for example, polygons,
Map data mainly composed of vector data for drawing lines, characters, and the like are stored in a hierarchical manner. The polygon data is for drawing, for example, a building or a site. The line data is for drawing, for example, a road or a railway. The character data includes, for example, character codes for drawing place names, building names, and the like, and data for drawing symbol marks such as icons and map symbols. Note that polygons and the like are merely examples, and the present invention is not limited to these. As will be described later with reference to FIGS. 5 and 6, each piece of geographic element data of polygons, lines, and characters is registered in a database formed by layering layers having different mesh sizes.

The entire map held by the map database 11 is divided by a number of meshes subdivided into longitude and latitude methods. Data for each mesh constitutes one file, and each data is assigned identification information for specifying position coordinates on the entire map and a representable mesh number.

The map server 10 transmits map data to the client computer 30 in the form of vector data. The drawing engine of the map display program 32 interprets the vector data and generates bitmap image data. As a result, a map in a range desired by the user is displayed on the display device 33. That is, the map server 10 stores the data requested by the client in the map database 1
1 and only returns it to the client and does not perform drawing processing. Therefore, the processing load on the map server 10 is reduced. Thereby, the map server 10 can immediately return the requested map data to each client even when receiving requests from many clients.

Next, a functional configuration of the map display program 32 will be described with reference to FIG.

The map display program 32 includes a display unit 320
And a downloader 323. The display unit 320 determines a range to be displayed on the map in response to the operation of scrolling or enlarging / reducing the map using the operation device 34 by the user. The display unit 320 selects a mesh file name (mesh number, indicated as “file ID” in the figure) necessary for the display range, and requests the download of the mesh file to the downloader 323. The display unit 320 draws a map image based on vector data included in the mesh file acquired from the downloader 323. Upon receiving the file acquisition request from the display unit 320, the downloader 323 requests the map server 10 to transmit the requested file, and downloads a necessary file from the map server 10.

The display unit 320 includes a cache management unit 321
To the memory cache 322 via the. In the memory cache 322, map data of the mesh acquired in the past via the downloader 323 is stored at a predetermined position.

The downloader 323 provides a download request list 327 (display section 320 displays the file name of the file to be downloaded (path name or file ID of the file stored in the map server 10) at any time). (Delete the file name in the file)
And a download flag 328 for notifying the display unit 320 whether or not a new file has been downloaded.
And a plurality of HTTP session threads 3 for each HTTP session when downloading each file
26A to 326D (four threads are shown, but the number is variable).

The downloader 323 can access the disk cache 325 formed in a large-capacity nonvolatile storage device such as an HDD device via the cache management unit 324. Disk cache 32
5 stores map data downloaded from the map server 10 at a predetermined position.

The map display program 32 determines the range to be displayed in accordance with the operation of the user, determines the number of meshes included in the display range (including the case where some are included), and determines the number of meshes required. Requests data from the map server 10. The map display program 32 requests map data for all meshes at all levels included in the display range. One mesh data is downloaded from the map server 10 to the client computer 30 by one HTTP session thread.

At this time, for example, small-scale data (high-level mesh data) such as small-scale (for example, national map) → medium-scale → large-scale (for example, city map)
By requesting the map server 10 for large-scale data (mesh data at a low level) from the map server 10, the map of the optimal scale can be gradually displayed (progressive display). Also, polygon data representing buildings and the like,
By displaying line data representing roads and the like and character data representing place names and the like in the order of acquisition, it is possible to smoothly and continuously display a map without giving stress to the user. When the display range is changed by a user operation, the map display program 32 does not request all the map data from the map server 10. This is because the already acquired map data is stored in the cache area 35 (the memory cache 322 and the disk cache 325).

Here, what should be noted are the properties and characteristics of the map information. The map information is different from a list in which names and the like are simply arranged in a predetermined order, and associates attributes and positions of geographic entities (buildings, roads, mountains and rivers). That is, the map information managed by the map server 10 is a spatial database that abstracts the real world, and is a data group that can be used continuously in a two-dimensional or three-dimensional space.
For this reason, for example, it is often used to refer to a surrounding area around a certain point, and it is unlikely that certain data will be used independently and discretely. Therefore, even when the display range changes, there is a high possibility that a part of the map data cached in the cache area 35 can be reused. Therefore, efficient management of the cache area 35 is important for the map display system.

FIG. 3 is an explanatory diagram showing the structure of the map database 11. The map database 11 has a hierarchical file structure as shown in FIG. 3, and the names of each directory and each file are composed of the minimum number of characters allowed by the OS. That is, each name of the root directory, sub-directory, and file is composed of one alphanumeric character. This directory structure is formed corresponding to the mesh number. Further, the mesh number is also included in the map data given the one-character file name.

That is, since the path to each file is set according to a predetermined rule based on the mesh number, the map display program 32 calculates the path of the predetermined file based on the mesh number of the necessary map data, Map server 10
Can request data transmission. Map server 10
Stores the file of the specified path in the map database 11
It just reads out from and returns it to the client.
The process of converting the mesh number into a path is handled by the map display program 32, and the map server 10 does not require any special function other than the function of responding to the HTTP request. Since the directory name and the file name are composed of one character as the minimum number of characters, the map display program 3
2, the amount of data when requesting data from the map server 10 can be reduced. In addition, as a result of limiting the number of characters, the hierarchy is divided, so that the number of subdirectories and files included in one directory can be limited, and the responsiveness to an HTTP request can be improved.

FIG. 4 is an explanatory diagram showing a data management method of the cache area 35.

As described above, the map database 11
Although it is constituted by a hierarchical file system having the name of the minimum number of characters, the map data to be held has a unique mesh number, and this mesh number is a value based on the position coordinates on the map. Map database 1
1 is stored in the cache area 35 of the client computer 30 and is reused as needed.

As described above, the map display program 32 generates a path to the map database 11 from the required map data mesh numbers. The map server 10 returns the requested map data to the client computer 30. Data M having mesh number (Xi, Yj)
When D is downloaded to the client side, the mesh data MD is stored at a predetermined position in the cache area. The array size of the cache area is set to Cnx, Cn
Assuming y, as shown in Equation 1, the remainder obtained by dividing the mesh number of the mesh data MD by the cache array size for each coordinate axis is the storage position in the cache area.

The storage position of the cache area = ((Xi mod Cnx), (Yj mod Cny)) (Equation 1) That is, the position where mesh data is stored in the cache area is uniquely determined by the mesh number. It is fixed. Therefore, when searching for data of a desired mesh in the cache area, the designated storage position is calculated from the mesh number of the data based on the above formula 1, and the data stored at the calculated position is directly examined. Is enough. That is, when searching for cache data, only the storage position determined from the mesh number need be searched, and the entire cache area is searched, or a cache data management table or the like is specially prepared for data search. No need.

On the other hand, when the data of the desired mesh does not exist at the designated storage position, the unnecessary data is deleted to release the memory area. Then, the data newly acquired from the map database 11 is stored in the designated storage position. In other words, when the user scrolls the map, the display range changes in the direction desired by the user, and with this change, old data is deleted (garbage collection) and new data is cached at the same time. Become. The relationship between the map base 11 and the disk cache 325 is not limited to the relationship between the map base 11 and the disk cache 325.
Similarly, data can be cached between the cache 325 and the memory cache 322 at a predetermined position uniquely determined from the mesh number.

Next, a method for registering map data in the map database 11 will be described with reference to FIGS.

First, FIG. 5 is a conceptual diagram in which a plurality of levels having different mesh sizes are hierarchized. In the present embodiment, a new concept of a plurality of levels having different mesh sizes is introduced. The mesh size in each level is the same and unchanged. In FIG. 5, four levels from level L0 to level Ln are shown, but only some of them are shown for convenience of explanation, and actually, more levels are hierarchized. .

From the lowest level L0 to the highest level L
The mesh size is set so as to gradually increase as n increases. The largest mesh size is set for the meshes constituting the highest level Ln. The maximum mesh size (Hn × Wn) is defined as a size that can include the largest object registered in the map database 11. That is, the largest object (for example, polygon data of the whole archipelago in the case of a Japanese map, polygon data of the shape of the prefecture to which the city belongs in the case of a city map, a place name, etc.) It is a mesh size that can be included. FIG.
In the above, the case where the highest level Ln is configured by a single mesh is illustrated, but this is for convenience of explanation.

FIG. 6 is an explanatory diagram showing a state in which objects are stored at levels having different mesh sizes. FIG.
When storing the polygonal object shown in (a) in the map database 11, first, as shown in FIG. 6B, a circumscribed area rectangle (bounding box) circumscribing the object is calculated. Next, as shown in FIG. 6C, it is determined at which level a minimum-size mesh that can accommodate the circumscribed rectangle of the object exists. Specifically, the mesh size is checked from the lowest level L0, and when the mesh size is smaller than the circumscribed rectangle,
Check the mesh size at the higher level. In FIG. 6, the mesh size ML3 of the level L3 is detected as the minimum size that accommodates the circumscribed rectangle of the object. Since the mesh size of the highest level Ln is set to be able to accommodate the largest object, any object can always be accommodated by the mesh of the highest level Ln.

After the level is determined, it is necessary to determine on which mesh of the level the object is to be registered. As long as the data is map data, the display position of the object is determined in advance based on the position of the geographical entity symbolized by the object. As shown in FIG. 6D, the object has four meshes ML3 (1) to M
When it exists across L3 (4), it becomes a problem which mesh is stored. In the conventional map display system, one object is originally divided into meshes and stored separately. However, in this case, a set of data is originally disjointed, and the data amount increases. It also takes time.

Therefore, in the present embodiment, a set of objects is stored as it is without being divided. Therefore, in the present embodiment, the mesh ML3 (1) where the coordinates P of the upper left corner of the rectangle circumscribing the object is located is determined as the storage destination of the object. Of course, other options are possible. For example, the mesh in which the center of gravity of the object is located can be selected as the storage destination, or the mesh in which the left end or the right end of the object itself is located instead of the coordinates of the circumscribed rectangle can be selected as the storage destination. . Alternatively, other coordinates such as the upper right corner and the lower left corner of the circumscribed rectangle can be used as a reference.

However, by using the coordinates of the circumscribed rectangle as a reference for selecting the storage destination, the storage destination selection processing is facilitated. Further, by using the upper left corner P of the circumscribed rectangle as a reference, the convenience increases when the object is character data. This is because, when only a part of a character is displayed on the display screen, displaying the head part (left side) of the character is more convenient for the user than displaying the end part (right side) of the character. Specifically, for example, when a part of the characters “*** building” is displayed, displaying “*** building” is easier to understand than displaying “ruding”. Since the upper left corner P is used as a reference instead of the lower left corner, the top part of the character string can be displayed with priority even in the case of vertical writing characters. Since the location of the object is determined based on the characteristics of the word reading horizontally from left to right and reading vertically from top to bottom, the map is displayed with words read from right to left In this case, the coordinates of the upper right corner may be adopted as a reference for selecting a storage destination.

Although the case where a circumscribed rectangle is used as the “circumscribed figure” has been described as an example, the present invention is not limited to this.
Other circumscribed figures such as circles and triangles can also be used.
When managing a three-dimensional object, a cuboid, a sphere, or the like may be adopted as the circumscribed figure. However,
Considering the convenience and efficiency of data registration, it can be said that it is more preferable to use a rectangle or a rectangular parallelepiped.

Next, the operation of the present embodiment will be described with reference to FIGS. The flowchart shown in the figure schematically shows the flow of the main part of the process, and is different from the actual program. Steps are abbreviated as “S”.

First, FIG. 7 shows a flow of the operation of the display unit 320.

When the user performs an operation to change the display range of the map, such as scrolling or enlarging or reducing the map (S1),
The display unit 320 performs the following operation in response to this. That is, all the file names described in the download request list 327 are deleted (S3), the download flag 328 is reset (S4), and a new display range after the change is determined and its display is performed. The file name (mesh number) of the mesh required for the range is determined (S5). As described later with reference to FIG. 10, all the meshes included in the display range and the mesh group adjacent to the left and upper left of the mesh group are determined as necessary meshes.

In step S5, the display unit 320 sets the optimal scale as the scale of the map to be displayed in the display range based on the display magnification determined by the scaling operation (for example, large scale if the display magnification is large, medium scale If it is a medium scale, and if it is small, it is a small scale), and for the map with the optimal scale, determine the file name required for the new display range (the file with the optimal scale determined here is referred to as the "required file" ). In addition, each of the smaller scales (ie, a larger denominator) than the optimal scale is used to provide a temporary alternate display when the required file of the optimal scale is not immediately available (ie, performing the progressive display described above). Also for the map of (1), the file name of the mesh that overlaps the new display range is determined (the map file of a smaller scale for this alternative display is hereinafter referred to as “alternative file”).

Next, the display unit 320 determines whether all of the polygon layer, the line layer, and the character layer have been displayed in the new display range (S6). If there is an object (data) for which display has not been completed, it is determined whether or not a file of the data is stored in the memory cache 322 (S7). Memory cache 322
If a necessary file or a substitute file remains, the file is read out, drawn, and displayed (S
8). As described above, since the storage position of each cache file in the memory cache 322 is determined based on the mesh number (file ID), it is necessary to directly access the file at the specified storage position to determine whether the file is a necessary file. Can be inspected. The cache data management process will be described in detail with reference to FIG.

If the required file or the substitute file does not exist in the memory cache 322 (S7: NO, S9: YE
S), a required file that was not found and a substitute file for the required file, and the memory cache 3
A file not found from the file 22 (hereinafter, collectively referred to as “missing file”) is requested to the downloader 323 (S10). As will be described later, when the downloader 323 receives a request for a missing file from the display unit 320, the downloader 323 performs the request in the requested order (first, the necessary file, and if it is not found, in order of the smaller-scale alternative file). Retrieve each missing file from disk cache 325. If a missing file is found, the downloader 32
3 returns the path to the file in the disk cache 325 to the display unit 320, and replies that there is no file if it cannot be found. The display unit 320 includes a downloader 323
If you receive the path to the file from (S11: YES),
The file is read from the disk cache 325 and stored in the memory cache 322 (S12), and a map image is drawn from the vector data of the file and displayed in a corresponding area of the display screen (S13).

On the other hand, if the missing file does not exist in the disk cache 325 (S11: NO), the presence or absence of the missing file is determined again (S14). Determine whether a change has occurred. If there is no change in the display range, the process waits until the download flag is set by the downloader 323 (S2). As described later, the downloader 323
Returns a response indicating that there is no file for a certain file, starts downloading the file from the map server 10, and when the file has been downloaded, stores the file in the disk cache 32.
5 and the download flag 328 is set.
When the download flag 328 is set (S2: YES),
The display unit 320 repeats the same processing as performed when the display range has changed. That is, all file names in the download request list 327 are deleted (S
3), and reset the download flag 328 (S
4) Recalculate the display range, determine a mesh file (mesh number) required for the display range (S5), acquire the file, and draw and display a map image.
9 and the following processing are repeated. Thereby, the display unit 320
Will draw and display the same map image again for meshes that have already been drawn and displayed, and for meshes for which files have been downloaded, copy the downloaded files to disk
The map image is read from the cache 325, rendered, and displayed in the mesh area.

Each time one missing file is downloaded, the display unit 320 repeats the processing from S3.
The display area on the screen gradually approaches completion one mesh at a time.
When the map image of the entire display area is completed (S6: YES), the display unit 320 returns to S1, waits for the display range to be changed by the user, and if changed, repeats the processing from S3 onward.

If the display range is changed by the user before the map image of the entire display area on the screen is completed (S15: YES), the display unit 320 repeats the processing of S3 and subsequent steps.

FIG. 8 shows the flow of the operation of the downloader 323.

Upon receiving a file request from the display unit 320 (S21), the downloader 323 searches for the requested file from the disk cache 325 (S2).
2). If the target file is found in the disk cache 325 (S22: YES), the downloader 323
Notifies the display unit 320 of the path of the file in the disk cache 325 (S23). Display 32
Display unit 320 displays the paths of all files requested from 0
(S24: NO), the downloader 323
The process returns to S21 and waits for a file request from the display unit 320 again.

On the other hand, if there is a file not stored in the disk cache 325 among the files requested from the display unit 320 (S24: YES), the downloader 323 determines that there is no file for the found file. To the display unit 320 (S25) and write the file ID of the file that was not found in the download request list 327 (S2).
6). As described above with reference to FIG. 7, since all the file names written in the past have been deleted from the download request list 327 by the display unit 320, only the ID of the file not found at this time must be written. become.

Next, when a file ID is described in the download request list 327 (S27: YE
S), the downloader 323 sequentially allocates the files described in the download request list 327 to the idle HTTP session threads 326A to 326D from the top of the list in order to acquire the files (S28). HTTP session thread 326A-3
When the file name is assigned, the 246 immediately executes an HTTP session with the map server 10 and downloads the assigned file from the map server 10.

Each time the download of an individual file is completed (S29: YES), the downloader 323 sends the file acquisition request to the download request list 32.
7 (S30), the downloaded file is stored in the disk cache 325 (S31), and the download flag 328 is set (S32). afterwards,
The downloader 323 returns to S21 and returns to the display unit 320.
Wait for another file request. download·
When the flag 328 is set, as described above, the display unit 320 issues a file request again, reads the downloaded file from the disk cache 325, draws the map image, and displays the map image. The downloader 3
23 is stored in the disk cache 325 at a predetermined storage location based on the mesh number.

The display unit 320 and the downloader 323 described above
In summary, the downloader 323 simply repeats downloading the missing file.
Further, the display unit 320 attempts to obtain all the files necessary for the display range every time a change in the display range or completion of file download occurs, and simply repeats the process of drawing the map using only the obtained files. Only. Therefore, it is possible to determine which file has been drawn and which file has not been drawn, and to perform a troublesome determination process of selectively drawing only undrawn files. In addition, the display unit 320 and the downloader 323 operate asynchronously, and do not perform a troublesome synchronous process such as adjusting the operation timing of both. As a result, a map image can be displayed at a high speed.

Further, since the drawing is performed by the client computer 30, the burden of drawing on the map server 10 is not imposed. This also speeds up the response of the map server 10 and contributes to the high-speed display of the map image.

Next, a method of managing cache data will be described with reference to FIG. 9 is performed by the memory cache 322 and the disk cache 325.
It is applicable in both.

First, the remainder of the required file ID (mesh number [Xi, Yj]) is divided by the cache size of the cache area for each coordinate axis (S41). At the storage position (Xi mod Cnx, Yj mod Cny) in the cache area (memory cache 322 or disk cache 325) thus obtained,
It is checked whether the desired file is stored (S
42, S43).

If the target file is stored in the storage location specified by the mesh number, the file is read and used (S44). If the target file is not stored in the specified storage location (S43: NO), it means that there is an unnecessary file previously used in the storage location, so delete the unnecessary file, The storage area is released (S45). Then, the file required in S41 is obtained from a higher-level storage device (such as the map database 11) and stored in a predetermined storage location (S46).

As described above, since the storage position in the cache area is specified in advance based on the mesh number, it is not necessary to confirm the location of the target file by referring to the cache management table or the like as in the related art. Can be directly inspected where the file is stored. Therefore, it is possible to speed up retrieval and reading of cache data, and realize high-speed map display by combining with the above-described configurations. Also,
If the target file is not cached in the specified storage location, the file stored in that storage location is determined to be unnecessary and immediately deleted, so priority is given to the cache management table as in the past. It is possible to efficiently delete unnecessary data (garbage collection) without the trouble of managing the degree.

Next, FIG. 10 is a flowchart showing a management method when various objects such as polygon data are stored in the map database 11.

First, it is determined whether the object is stored or extracted (S51). If the object is stored, a rectangle circumscribing the object is calculated as described above with reference to FIG. 6 (S52). . Then, the following processing is performed to determine at which level the data is to be stored. That is, the level number is set to the lowest level as an initial value for checking the mesh size (S53), and it is determined whether or not the mesh size at that level is equal to or larger than the size of the circumscribed rectangle (S54). If the mesh size is smaller than the circumscribed rectangle (S54: NO), the level number is incremented by one (S55), and the mesh size and the size of the circumscribed rectangle are compared again in S54.

If a level having a mesh size equal to or larger than the size of the circumscribed rectangle is detected (S54: YES), a mesh in which the coordinates of the upper left corner of the circumscribed rectangle is located among the meshes including the circumscribed rectangle is detected. (S56). In addition,
The circumscribed rectangle of the object may fit within one mesh, or may extend over a maximum of four meshes as shown in FIG. Then, the mesh in which the coordinates of the upper left corner of the circumscribed rectangle are located is selected as the storage destination of the object, and the data of the object is associated with the mesh and registered in the map database 11 (S57).

On the other hand, in the case of taking out (reading out) an object, data of all the mesh groups included in the range necessary for map display and the mesh groups located on the left side and the upper side of the mesh group are taken out (S58). This is because, in order to register the object in association with the mesh in which the upper left corner of the circumscribed rectangle of the object is located, data of a mesh around the mesh in addition to the mesh directly included in the display range is required.

As described above, in order to register various objects such as polygons and characters in association with a mesh including a rectangle circumscribing the object and register the objects, a plurality of mesh objects are divided for each mesh as in the prior art. It is possible to handle a group of data without registration. Therefore, an increase in the amount of data can be prevented, high-speed data processing can be performed, and in combination with the above-described configurations, a faster and smoother map display can be realized.

The present invention is not limited to the above embodiment. A person skilled in the art can make various modifications such as adding a new addition or change to the configuration of the embodiment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic overall configuration of an embodiment of a map display system according to the present invention.

FIG. 2 is a block diagram showing a functional configuration of a map display program.

FIG. 3 is an explanatory diagram showing a hierarchical file system of a map server.

FIG. 4 is an explanatory diagram showing a cache method.

FIG. 5 is a conceptual diagram of a storage space in which levels having different mesh sizes are hierarchized.

FIG. 6 is an explanatory diagram showing a method of storing objects.

FIG. 7 is a flowchart illustrating an operation of a display unit.

FIG. 8 is a flowchart showing the operation of the downloader.

FIG. 9 is a flowchart illustrating a cache data management method.

FIG. 10 is a flowchart illustrating an object management method.

[Explanation of symbols]

 Reference Signs List 10 map server 11 map database 20 internet 30 client computer 31 client program 32 map display program 33 display device 34 operation device 35 cache area

Claims (13)

[Claims] 1. A method according to claim 1, wherein a predetermined amount of data is stored in a first storage device that holds a large number of data in an n-dimensional first storage space and a second storage device that has a second storage space smaller than the first storage space. In a data management device for transferring and managing data, storage position setting means for setting a designated storage position in the second storage space in advance for each of the plurality of data held in the first storage space, Data acquisition means for retrieving predetermined data from the first storage space and storing the retrieved data in a specified storage location set in the data; and the predetermined data is not stored in the specified storage location A data deleting unit that deletes data already stored in the designated storage location. 2. The storage position setting means sets each of the designated storage positions by assigning in advance each coordinate value of the first storage space to each coordinate value of the second storage space. The data management device according to claim 1. 3. The storage position setting means sets each of the designated storage positions by equally allocating each coordinate value of the first storage space to each coordinate value of the second storage space. The data management device according to claim 1, wherein 4. The storage position setting means calculates a remainder value obtained by dividing each coordinate value of the first storage space to which a continuous integer value is assigned by the size of the second storage space. 2. The data management device according to claim 1, wherein a coordinate value in the second storage space indicated by the remaining value is set in advance as the designated storage position. 5. The first storage space stores data that can be used continuously in an n-dimensional space with coordinate values of integer values determined according to positions in the n-dimensional space. The setting means calculates a remainder value obtained by dividing each coordinate value of the first storage space by the size of the second storage space, and calculates the second storage space indicated by the remainder value. 2. The data management device according to claim 1, wherein coordinate values in the data are set in advance as the designated storage position. 6. A method according to claim 1, wherein the first storage device holding a large number of data in the n-dimensional first storage space is transferred from the first storage device to a second storage device having a second storage space smaller than the first storage space. In the data management method for transferring and managing data, a designated storage position in the second storage space is set in advance for each of the plurality of data held in the first storage space, and Determining whether the data is stored in a designated storage location set in the data; and, if the designated data is not stored in the designated storage location, storing the data in the designated storage location. Deleting the specified data; obtaining the specified data by searching the first storage space; and setting the obtained data in the data. Data management method comprising the step of storing in the storage location designated, to comprise was. 7. The data management method according to claim 6, wherein the data is continuously usable in an n-dimensional space. 8. A program for transferring and managing predetermined data from an n-dimensional first storage space to a second storage space smaller than the first storage space, wherein the first storage space And a function of assigning each coordinate value to the coordinate value of the second storage space, and data specified with the coordinate value of the first storage space are stored in corresponding coordinate values of the second storage space. A function of determining whether or not the specified data is stored in the corresponding coordinate value of the second storage space, the data already stored in the coordinate value is stored in the second storage space. A function of deleting from the storage space, a function of acquiring the specified data from the first storage space, and a function of storing the acquired data in a corresponding coordinate value of the second storage space. Implemented on computer A program for causing. 9. A map server having whole map data subdivided into a large number of fragment map data, a desired fragment map data received from the map server via a communication network, and a map image is formed from the received fragment map data. And a client for drawing and displaying the map data. The client holds the fragment map data received from the map server in a cache memory having a storage space smaller than a storage space of the map server. A cache data management device, the cache data management device comprising: a coordinate allocation unit that allocates each coordinate value of the storage space of the map server to a coordinate value in the storage space of the cache memory; Search and assign the searched data to the data Data acquisition means for storing the coordinate data in the cache memory; and when the predetermined data is not stored in the cache memory in the allocated coordinate value, the data already stored in the coordinate value is stored in the cache memory. A map display system comprising: data deletion means for deleting data from a cache memory. 10. A data management apparatus comprising: a server for storing data; and a client for obtaining data from the server, wherein the server stores a plurality of files to which identification information is assigned in a hierarchical manner. Wherein a name of each directory and each file is constituted by a minimum number of characters, and the client converts a path name in the file system based on identification information given to a file of desired data, Requesting means for requesting the server to transmit the desired data based on the path name obtained by the converting means. 11. A map server having whole map data subdivided into a large number of fragment map data, a desired fragment map data is received from the map server via a communication network, and a map image is formed from the received fragment map data. A map display system comprising a client for drawing and displaying a plurality of directory names, wherein the map server comprises: a hierarchical file system in which each directory name has a minimum number of characters; The client stores fragment map data, and the client converts identification information assigned to each of the fragment map data based on a position in a map space into a path name in a hierarchical file system including the minimum number of characters. Requesting the map server for desired data. Diagrammatic representation system. 12. A map server having whole map data subdivided into a large number of fragmented map data, a desired fragmented map data is received from the map server via a communication network, and a map image is formed from the received fragmented map data. (1) the map server is provided based on a position in a map space to a hierarchical file system in which each directory name is composed of a minimum number of characters. The plurality of pieces of fragment map data having identification information are respectively stored with file names having the minimum number of characters, and (2) the client stores (2a) the fragment map data received from the map server in the map server. Data management apparatus for storing data in a cache memory having a storage space smaller than the storage space And (2b) a data request device for requesting predetermined data by converting the identification information into a path name in a hierarchical file system composed of the minimum number of characters, and (3) the cache data management device. (3a) a coordinate allocating means for allocating the identification information to a coordinate value in the storage space of the cache memory; and (3b) a coordinate allocated to the data obtained from the map server via the data request device. (3c) when the predetermined data is not stored in the cache memory in the assigned coordinate value, the data already stored in the coordinate value is stored in the cache memory. And a data deleting means for deleting data from the cache memory. Display system. 13. The map display system according to claim 9, wherein the fragment map data is map data representing individual geographic elements included in a map image represented by the whole map data.