The Metadata System of China Mete Data Service

The Metadata System of China Mete. Data Service System WANG Guofu wanggf@cma. gov. cn National Meteorological Information Centre, CMA Metadata Workshop 27 -29 Sept. 2005

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

Main Server Observing data service web site Low temp. data service Satellite data service web site Scientific research data service web site Drought data service web site Meiyu data service web site Qinghai-Tibet data web site Torrential rain and flood data service web site National Meteorological Information Centre, CMA

What’s the metadata system? Includes: n q metadata publish servers: § publish, metadata management, interface q metadata gateway: § proxy server, node management q metadatabases q XML metadata editor Metada ta Publish Server Metada ta Gatewa y Metada ta Databa se Metadata Editor Monitor and control node National Meteorological Information Centre, CMA

Infrastructure of Metadata System Register Metadata Server Metadata Database Web Server Gateway HTTP protocol Z 39. 50 protocol National Meteorological Information Centre, CMA

Monitor and node control gateway intern et Metadata server Metadatabase -A Metadatabase -B Metadata server Metadatabase -C National Meteorological Information Centre, CMA

Monitor and node control Gateway intern et Metadata server Metadata database National Meteorological Information Centre, CMA

Edit metadata Web Server Gateway database registe r Metadata server documents Metadata Editor Metadatabase XML database others National Meteorological Information Centre, CMA

Besides metadatabase, database … Catalogue? • Sub- WMO Core: Title(search), Data category(navigation), Keywords(search), On-line Gateway source(location), Abstract(search), use. Limitation etc • Node information • Location of Metadata Database • Update every day ª ª Metadata Server Metadata Database ª ……. Metadata Server Metadata Database National Meteorological Information Centre, CMA

Where we used the metadata ? q Discovery of data By Metadata system, user can locate the datasets from the catalogues quickly first, then go to the XML metadatabase and get it. q Determining data fitness for use Users can determine if the dataset meets their needs by understanding the metadata elements. q Data access After locating and determining if a dataset meet their needs, users may do query or download data (need registration). q 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

Data Discovery Client App. Server User send request using web interface Determining Transform data fitness the results for use to web pages Web Server Gateway creates SQL by Assemble request and message and sent to locating, then gateway send to the located web site Metadata Server Metadata DB Do XML query and extract information Assemble the query results as message National Meteorological Information Centre, CMA

Data Access Client App Server Web. Server Datasets If meet the needs, get the location of dataset (for example, through a URL) Identification of user Exe. HTTP or FTP download File system Do SQL Database system National Meteorological Information Centre, CMA

Summery q Distinguish the “metadata” into: q Metadata for data set– WMO Core is good to use q Metadata for data access (Query)– design as your system developing q Metadata for data– go with the data set, for example “data dictionary”, station information q Maintain and manage the metadata in every centre, need the update mechanism National Meteorological Information Centre, CMA

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