KR20020045328A - Search method of distributed/heterogeneous gis databases using metadata interchange standard - Google Patents

Abstract

PURPOSE: A distributed different database search method using an XMI(XML Metadata Interchange) is provided to search a position of a GIS(Geographic Information System) DB and a schema relating to the position. CONSTITUTION: Each GIS DB(10,20,30) encodes the information into an XML(extensible Markup Language) document of an XMI format by using an XMI conversion program after expressing an independent DB schema as a UML(Unified Modeling Language). IF a URL(Uniform Resource Locator) of each XML file is registered to a meta search server(40), the server stores each DB schema information extracted from the XMI file by an XML parser in an XMI DB(50). If the user connecting to the server requests a GIS information search, the server dynamically generates an SQL(Structured Query Language) query matching to each DB schema by inquiring to the XMI DB and displays a result of the query to the user.

Description

Distributed heterogeneous database search using metadata exchange standard {SEARCH METHOD OF DISTRIBUTED / HETEROGENEOUS GIS DATABASES USING METADATA INTERCHANGE STANDARD}

The present invention relates to a database search method, and more particularly, to a distributed / heterogeneous GIS database search method using a metadata exchange standard (XMI).

Recently, as network spread and utilization of geographic information increase, the importance of effective exchange and access of geographic information is emphasized. For this purpose, when geographic information is stored in a Geographic Information System (GIS) database, metadata about the GIS data is used. Information will also be stored. This is because the use of such metadata is not only an advantage of facilitating the search for specific geographic information desired by the user, but also helps in the systematic management of a large variety of geographic information. However, since GIS data is generated by several geographically separated departments or organizations and stored and managed in a GIS database based on a unique database schema, the information retrieval function is dependent on a specific GIS storage environment, and information interoperability is difficult. International standards for GIS metadata have been enacted in ISO / TC211, but in reality, local GIS metadata schemas are used that are similar but differ slightly to suit the situation of the country.

An example of a representative information system that uses GIS metadata is a spatial information distribution organization called Clearinghouse. It is a system that integrates and manages GIS information at a large organization or country level, and stores metadata about registered GIS data. When a user requests specific information, it retrieves information from its database that matches the condition.

However, since the aforementioned clearing house also uses metadata schemas that differ between countries or organizations, there is a limit in that a search service is supported only for countries or organizations that use the same GIS metadata. On the other hand, the user should be able to query the information he / she wants and get the result even if he does not know which GIS database is geographically located and what schema is stored in the GIS information stored in the database. .

Accordingly, an object of the present invention is to provide a distributed heterogeneous database search method using a metadata exchange standard that can provide a transparent search function for a specific GIS database location and its associated schema. Is in.

Another object of the present invention is to provide users with a comprehensive search function transparent to the metadata schema as well as the location of a specific GIS database, as well as distributed heterogeneous using a metadata exchange standard that can search information dependent on a specific GIS database schema. It provides a database search method.

1 is a schematic diagram of a metadata retrieval system according to an embodiment of the present invention;

2 is a block diagram of a metadata retrieval system according to an embodiment of the present invention.

3 is an exemplary diagram of main components of a client 60 and a meta search server 40 in a meta search system configuration according to an embodiment of the present invention.

4 illustrates a UML representation of a GIS metadata standard in accordance with an embodiment of the present invention.

5 is an exemplary UML representation of a SQL Server GIS database schema in accordance with an embodiment of the present invention.

6 is an exemplary UML representation of an Oracle GIS database schema in accordance with an embodiment of the present invention.

7 is an exemplary UML representation of a MiniSQL GIS database schema in accordance with an embodiment of the present invention.

8 illustrates a conceptual schema of an XMI database according to an embodiment of the present invention.

9 illustrates a user interface according to an embodiment of the present invention.

10 is an exemplary user interface for the integrated information retrieval.

11 illustrates an example of a user interface for visualizing a search result.

In order to achieve the above object, the present invention provides a metadata search system in which a plurality of GIS databases, a client, and a meta search server are connected through a communication network.

Each GIS database side expresses its own database schema in UML and encodes and stores the information in XMI format XML document using XMI conversion program.

Registering the URL of each XML file with the meta search server, the server extracts each database schema information contained in the XMI file with an XML parser and stores the information in the XMI database;

When there is a request for retrieving GIS information from any client connected to the server, the server queries the XMI database to dynamically generate a query to which GIS databases and a SQL query appropriate for each database schema. It is characterized by consisting of the process of transmitting the result according to the client.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the annexed drawings, many specific details are set forth in order to provide a more thorough understanding of the present invention, such as the number of GIS databases, examples of user interfaces, and specific processing flows. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Meanwhile, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

First, FIG. 1 is a schematic diagram of a metadata retrieval system according to an embodiment of the present invention, and is a view for briefly explaining a distributed heterogeneous database retrieval method using a metadata exchange standard according to an embodiment of the present invention. In FIG. 1, each GIS database side 10, 20, 30 expresses its own database schema in UML (Unified Modeling Language), and then uses the XMI (Metadata Interchange Standard) conversion program for information in an XML document in XMI format. Encode. When the URL (Universal Resource Location) of each XML file is registered in the meta search server 40, the server 40 is an XML parser and contains information about each database schema (class and attribute information) contained in the XMI file. ) Is extracted and stored in the XMI database 50. If any user accessing the server 40 requests GIS information retrieval, the server 40 queries the XMI database 50 to determine which GIS databases are to be sent to and which is appropriate for each database schema. Generates a SQL (Structured Query Language) query statement dynamically and shows the result of the query to the user.

Hereinafter, the outline of the present invention described above will be described in more detail.

2 illustrates a configuration of a metadata retrieval system according to an embodiment of the present invention. Referring to FIG. 2, when the user 60 accesses the meta search server 40, the user 60 loads an applet and operates as a CORBA (Common Object Request Broker Architecture) client. Middleware uses CORBA, which extracts specific GIS database schema information from the XMI file, interfaces with the XMI database, and provides different types of GIS databases at the back-end and through Java DataBase Connectivity (JDBC). It is in charge of inquiring and returning information. The XMI database 50 is a storage location that integrates and manages each GIS database schema information and other additional information (access account, URL, etc.). The implementation uses an object store OODBMS (Object Oriented Database Management System).

On the other hand, as the implementation environment, since the client 60 side is a swing-based Java applet, it is possible wherever the Internet is available. The meta search server 40 used OrbixWeb 3.0 as CORBA under Solaris 2.6, and the Object Store 5.1 OODBMS as the XMI database 50. JDBC drivers for JDBC connections to other relational databases used drivers of type 3 or 4 among four types. The GIS database 50 uses only three relational databases: SQL Server 7, Oracle 7.3, and MiniSQL 1.0. Java is JDK 1.1.7, the XML parser uses Oracle Parser 2.0 and the Rational Rose UML tool for conceptual schema modeling of each database, and the XMI transformation toolkit provided by IBM for XMI encoding.

Hereinafter, main components of the client 60 and the meta search server 40 will be described with reference to FIG. 3.

3 is a diagram illustrating an example of main components of the client 60 and the meta search server 40 in the meta search system configuration according to an embodiment of the present invention, and more specifically, the client 60 side and the server 40. It shows the functional modules for performing a task that must be processed at the side.

Referring to FIG. 3, first, a new GIS database registration processing module 62 on the client 60 side provides an interface and information processing function for a registrant to search for and register a specific GIS database with the server 40. The dynamic generation module 64 of the UI for classification search and database-specific search plays a role of generating various classification search interfaces and related result frames provided to the user through the information inquiry in the XMI database 50. The input / output data processing modules 66 and 46 for CORBA communication are responsible for processing data or messages communicated between both ends of the CORBA system.

On the other hand, the module 42 for extracting GIS metadata schema information from the XMI file on the meta search server 40 side automatically extracts schema information (class and related attribute information in the implementation) from the XMI file of the newly registered GIS database. Database it. The automatic SQL generation module 44 for classification search generates a query for each specific GIS database to which a query is to be sent according to a keyword inputted by a user and a search option. The query processing module 45 through JDBC is responsible for connecting / querying / returning results to various kinds of relational GIS databases.

Hereinafter, an application example of the present invention will be described. First, FIG. 4 illustrates a UML representation of a GIS metadata standard according to an embodiment of the present invention. In detail, FIG. 4 illustrates a Content Standards for Digital Geospatial Metadata (CSDGM) of the US FGDC. The relationship between the major metadata sections extracted from the Korea National Geographic Institute's external metadata and numerical data is expressed in UML. Considering the central Digital DataSet as reference information for numerical data, the seven classes represented by the stereotype << include >> around it are divided into sections and sections from the aforementioned metadata standards. The sub information included in the section. Among the properties of digital dataset class, mapID and typeOfMapID mean mapIDdml type and identifier which can distinguish numerical data. For example, mapID can be a foreign key or object reference to a numeric data table that is associated with metadata for a GIS database, and is a simple GIS metadata database that can identify any numeric data, such as a section number. Play a role. Metadata sections associated with a single digital dataset, i.e., numeric data, include data identification, data quality, history, spatial reference information, metadata reference, metadata reference, Spatial Data Organization (Spatial Data Organization), Distribution Information (DistributionInformation), etc. are classified into the data type of each metadata class is set to a string.

5 is an exemplary UML representation of a SQL Server GIS database schema in accordance with an embodiment of the present invention. In more detail, FIG. 5 is a UML representation of numeric data and associated metadata schema for a SQL server database. In the present invention, since the relational database is targeted, each table has a primary key. The type of kit value is set to int (integer type), and the name of the key is composed of the table name + ID for all tables except the digital data set. The types of the other side attributes are all set to strings for simplicity. Of course, the data type used when actually storing GIS information in a database is used by selecting an appropriate number or string type provided by each DBMS.

FIG. 6 is a UML representation of an Oracle GIS database schema according to an embodiment of the present invention, and FIG. 7 is an exemplary diagram of a UML representation of a MiniSQL GIS database schema.

A brief comparison of the differences between the three database schemas described above shows that the identity class is common to the schemas of SQL Server and Oracle, but each database schema is configured to have one non-common metadata class except the identifier. did. The schema of MiniSQL has an identifier class, but there are differences in the number of identifier classes and attributes defined in the schema of SQL Server or Oracle. And the SpatialReferenceInfo class is not in the other two database schemas mentioned earlier.

First, each metadata schema part is expressed in UML and then converted to an XMI file based on the UML metamodel using the XMI toolkit provided by IBM.

Hereinafter, the process of extracting schema information from an XMI file will be described. First, the XMI standard format is basically a well-formed and valid XML document, and generally has the following structure.

First, in the case of the document type definition (DTD), the XMI file converted from each GIS database schema of the present system is based on UML. Therefore, uml.dtd is referred to as an external DTD. It has XMI as the root element of the top level. Under the root element, various modeling elements (classes, attributes, methods, etc.) and the characteristics (visibility, relationship type, frequency, etc.) of the related modeling elements can be optionally described. When the URL of the XMI file having such schema information is registered in the meta search server 40, the server 40 parses and obtains metadata schema information of the database using an XML parser. XML parser mainly includes Document Object Model (DOM) and Simple API for XML (SAX). The implementation module of this system extracts class and related property information from GIS database schema information using SAX event-based API. XMI database.

Referring to the design of the XMI database, in the embodiment of the present invention, the object store OODBMS is first used as the XMI database. 8 illustrates some of the core classes and related operations of the conceptual schema of the XMI database as UML class diagrams. Although all classes shown in FIG. 8 are persistent, DatabaseRoot and SchemaRoot play independent roles in any GIS database, and xxxDescriptor manages information dependent on a specific GIS database.

A database root is an entry object that acts as an iterator to access information in each database descriptor after a session of a database begins. Schema root is configured to manage the union of attributes of registered database schema. Thus, if an attribute of any class in the newly registered database schema has the same name and type as the existing one managed by the schema root, it will only have a reference to the previously created AttrDescriptordp. This convenience class not only saves the complexity of computationally retrieving all existing database schemas during dynamic configuration of the user interface or automatic query generation, but also the unnecessary database space caused by the duplication of attributes in each database schema. Waste can be prevented. In a UML representation, an association is all a reference to an object stored in the persistent domain.

On the other hand, the automatic generation mechanism of SQL statements for search keywords will be described. According to the present invention, GIS database schemas are configured in a 1: 1 relationship with other metadata sessions around a numerical data reference table called a digital dataset. It was. For a particular database schema to send a query to, the total number of metadata-related tables, including digital datasets, is n, and k is the number of search keywords entered by the user (each search keyword is derived from different tables in the schema). Assuming that it is associated with an attribute), the query is generated in the form of a text box below.

Items with sel_ in front of an element, such as sel_table (1), sel_table (k) .sel_field, represent names associated with the table or attribute to which the search keyword is entered, and keyword_1 and keyword_k are identifiers for the entered keyword. .

First, the records are obtained by searching the selected table and attribute, and then the key of the digital data set table (numerical reference table) is obtained through the relational operation. Once you have the primary keys of the digital dataset associated with the search results, you get all the records associated with the rest of the tables through a join operation around the digital dataset table. Therefore, query result processed through JDBC is returned as one table through join of all related metadata tables. The resulting data is sent to the client side via COVA, and the applet receives the results from each database and displays the relevant information of each database site and metadata of the relevant numerical data in the result frame.

Therefore, the query request and information return for each relational DBMS ends as one JDBC connection.

In the embodiment of the present invention to illustrate the form of the automatically generated SQL statement as follows.

SELECT * (or table [1]. *, Table [2]. *, ..., table [n]. *)

FROMtable [1], table [2], .., table [n-1], table [n]

WHEREtable [1] .id = {DigitalDataSet} .id

AND ...

ANDtable [n-k-l] .id = {DigitalDataSet} .id

AND {DigitalDataSet} .id = sel_table [1] .id

AND [UPPER] sel_table [1] .sel_field [LIKE] [UPPER] ('% keyword_1%')

AND ...

AND {DigitalDataSet} .id = sel_table [k] .id

AND [UPPER] sel_table [k] .sel_field [LIKE] [UPPER] ('% keyword_k%')

Hereinafter, a user interface according to an exemplary embodiment of the present invention will be described with reference to FIGS. 9 through 11.

9 illustrates an example of a user interface according to an exemplary embodiment of the present invention, and FIG. 10 illustrates an example of a user interface for searching integrated information. 11 illustrates an example of a user interface for visualizing a search result.

Referring to FIG. 9, a new GIS database registration is described. When a registration is first selected, a registration related interface prepared in advance appears as shown in FIG. 9, and the user inputs a user account for the location, type, and access of the database to be registered. , And the URL of the XMI file. The XMI file is the result of modeling the metadata part of the schema of the GIS database to be registered with UML and converting the XMI. The server 40 receives the input information, extracts the class and attribute information from the XMI file using the XML parser, and stores the database information and the extracted schema information in the database.

Referring to FIG. 10, a user inputs a keyword in a text box next to an attribute to search, sets a search option at the top, and selects a search button. In the applet, the input field is null. Only the text fields, not), will message the class name, attribute name, and keyword and send them to the COVA server side.

Referring to FIG. 11, the search result interface is described. For the quality of the client, the server side queries the delivered search term message and schema information in the XMI database, obtains a list and access information of a database to which a query request is sent, and obtains structure information. Pass automatically to the module that composes the SQL query. In this case, the query is performed on an attribute of one specific table in the RDB, and the result processed through JDBC is returned as a result set consisting of joins of all metadata tables. When the result of the server side is transmitted to the client applet, the applet shows the combined information and the search result of the GIS database which obtained the query result as one table as shown in FIG.

Therefore, the user can query the information he / she wants and get the result without knowing which GIS database is geographically located in the GIS database and which schema the GIS information stored in the database is stored.

As described above, the present invention has an advantage of providing a transparent search function for various GIS database locations and related database schemas, which can be arbitrarily obtained using XMI, which is a metadata exchange standard of GIS metadata and OMG. By analyzing the schema information of the database and making a database on the meta search server side, and providing it to the user through inquiry about it if necessary, it is possible to provide improved classification search service and transparency for various GIS databases.

In addition, since the implementation uses CORBA as middleware and the back-end various GIS databases and the communication mechanism with the COVA server side use JDBC, the meta search server is platform-independent and highly scalable. There is this. In addition, the platform-side Java applet is used as the client-side interface, which provides users with a web-based interface that is easy to access and use.

Claims (3)

In a metadata retrieval system in which a plurality of GIS databases, a client, and a meta retrieval server are connected through a communication network, Each GIS database side expresses its own database schema in UML and encodes and stores the information in XMI format XML document using XMI conversion program. Registering the URL of each XML file with the meta search server, the server extracts each database schema information contained in the XMI file with an XML parser and stores the information in the XMI database; When there is a request for retrieving GIS information from any client connected to the server, the server queries the XMI database to dynamically generate which SQL queries to send to which GIS databases and to query the corresponding database schema. Distributed heterogeneous database retrieval method using metadata exchange standard (XMI), characterized in that the process of transmitting the result according to the client. The method of claim 1, wherein the XMI database is implemented as an object store (OODBMS) as an object store (OODBMS) as a storage location for managing all the GIS database schema information, and additional information such as access account and URL. Distributed heterogeneous database retrieval method using metadata exchange standard (XMI). The distributed heterogeneous database retrieval method of claim 1, wherein the database schema information includes at least class and attribute information.