1. The Metadata System of C hina M ete. D ata S ervice S ystem WANG Guofu wanggf@cma.gov.cn National Meteorological Information Centre, CMA Metadata Workshop 27-29 Sept. 2005

2. National Meteorological Information Centre, CMA What’s the data service system? First, it’s a distributed service system (distributed in physical existence and unified in logics). Every data centre maintains and manages its XML metadata data base data service Second, the system is jointly constituted by national data service web site, and provincial special topic data service web sites. Third, it makes up: Web sites (for data access) Metadata system (for data discovery) Security identity authentication system

3. 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

4. National Meteorological Information Centre, CMA What’s the metadata 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

5. Metadata Server Gateway Z39.50 protocol HTTP protocol Register Web Server Metadata Database Infrastructure of Metadata System

6. National Meteorological Information Centre, CMA Metadata database -A Metadata server Metadata database -B Metadata database -C gateway interne t Metadata database Metadata server Metadata database Metadata server Monitor and node control

7. National Meteorological Information Centre, CMA Monitor and node control Gateway Metadata database Metadata server Metadata database Metadata server Metadata database Metadata server interne t

8. National Meteorological Information Centre, CMA Metadata database Metadata server Edit metadata database XML database documents others Metadata Editor Gateway Web Server register

9. National Meteorological Information Centre, CMA Metadata Database Metadata Server Metadata Database Metadata Server Metadata Database Metadata Server Gateway Catalogue? ……. Besides metadata database Besides 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   

10. National Meteorological Information Centre, CMA Where we used the metadata ?  Discovery of data By Metadata system, user can locate the datasets from the catalogues quickly first, then 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.

11. National Meteorological Information Centre, CMA ClientApp. Server Web ServerGatewayMetadata 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 Discovery

12. National Meteorological Information Centre, CMA ClientApp ServerWebServerDatasets 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 Access

13. National Meteorological Information Centre, CMASummery  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

14. Welcome to http://cdc.cma.gov.cn http://data.cma.gov.cn