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The Metadata System of
China Mete. Data Service System
WANG Guofu
National Meteorological Information Centre, CMA
Metadata Workshop 27-29 Sept. 2005
National Meteorological Information Centre, CMA
What’s the data service What’s the data service system?system?
First, it’s a distributed service system (distributed in physical existence an
d unified in logics). Every data centre maintains and manages its XML meta
data data base
Second, the system is jointly constituted by national data service web site,
and provincial special topic data servicedata service web sites.
Third, it makes up:
Web sites (for data access)
Metadata system (for data discovery)
Security identity authentication system
National Meteorological Information Centre, CMA
Main Server
Observing data service web site
Satellite data service web site
Scientific research data service web site
Qinghai-Tibet data web site
Drought data service web site
Low temp. data service
Torrential rain and flood data service web site
Meiyu data service web site
National Meteorological Information Centre, CMA
What’s the metadata What’s the metadata system?system?
Includes:
metadata publish servers:
publish, metadata management,
interface
metadata gateway:
proxy server, node management
metadata databases
XML metadata editor
Metadata Publish Server Metadata
Database
Metadata Gateway
Metadata Editor
Monitor and control node
Metadata Server
Gateway
Z39.50 protocolHTTP protocol
RegisterRegister
Web ServerWeb Server
MetadataDatabase
Infrastructure of Metadata System
National Meteorological Information Centre, CMA
Metadata database -A
Metadata server
Metadata database -B
Metadata database -C
gateway
internet
Metadata database
Metadata server
Metadata database
Metadata server
Monitor and node controlMonitor and node control
National Meteorological Information Centre, CMA
Monitor and node controlMonitor and node control
Gateway
Metadata database
Metadata server
Metadata database
Metadata server
Metadata database
Metadata server
internet
National Meteorological Information Centre, CMA
Metadata database
Metadata server
Edit metadataEdit metadata
database
XML database
documents
others
Metadata Editor
Gateway
Web Server
register
National Meteorological Information Centre, CMA
Metadata Database
Metadata Server
MetadataDatabase
Metadata Server
Metadata Database
Metadata Server
Gateway
Catalogue?Catalogue?
…….
Besides metadata databaseBesides metadata database, …
• Sub- WMO Core: Title(search),
Data category(navigation),
Keywords(search), On-line
source(location), Abstract(search),
useLimitation etc
• Node information• Location of Metadata Database •Update every day
National Meteorological Information Centre, CMA
Where we used the Where we used the metadata ?metadata ?
Discovery of data
By Metadata system, user can locate the datasets from the catalogues quickly first, t
hen go to the XML metadata database and get it.
Determining data fitness for use
Users can determine if the dataset meets their needs by understanding the metadata
elements.
Data access
After locating and determining if a dataset meet their needs, users may do query or
download data (need registration).
Data application
Metadata elements have been selected, so that users know how to process, apply,
merge a particular dataset with others, as well as understanding the limitations
of the data.
National Meteorological Information Centre, CMA
Client App. Server
Web Server Gateway Metadata Server
Metadata DB
User send request
using web
interface
creates SQL by request and
sent to gateway
Assemble message and locating, then send to the located web
site
Do XML query and extract information
Determining data fitness
for use
Transform the results
to web pages
Assemble the query results as message
Data DiscoveryData Discovery
National Meteorological Information Centre, CMA
Client App Server WebServer Datasets
If meet the needs, get the location of dataset (for example, through a URL)
Identification of user
Exe. HTTP or FTP download
Do SQL
File system
Database system
Data AccessData Access
National Meteorological Information Centre, CMA
SummerySummery
Distinguish the “metadata” into:
Metadata for data set– WMO Core is good to use
Metadata for data access (Query)– design as your system
developing
Metadata for data– go with the data set, for example “data
dictionary”, station information
Maintain and manage the metadata in every centre, need the
update mechanism
Welcome to
http://cdc.cma.gov.cn
http://data.cma.gov.cn
