F. Toussaint (PIK, Potsdam), M. Lautenschlager (DKRZ, Hamburg), M. Reinke (AWI, Bremerhaven)

The CERA Database Structure

What are CERA and AFRI ?

• Climate and Environmental Data Retrieval and Archiving System: a database (DB) structure of tables to store spatial data and metadata
• A Flexible Retrieval Interface: a web/Java-based graphical user interface (GUI) to generate DB queries
• Interactive Digital Atlas: an IO facility, allowing for region selection, station display, and more... - integrated into AFRI
• diagram

Why Federated (Meta) Data ?

• to match the requirements for geographically distributed data storage in different institutions
• less expenses for tools, user interfaces, installation
• problem: very inhomogenious data of different structures

Requirements

• common, transparent access to (meta) data of all project partners
• high flexibility for all kinds of spatial data (model, station and other)
• open structure; as far as possible: simple structure
• compatibility to content standards (NASA-DIF, FGDC-CSDGM etc.) and functional standards (IEEE etc.)

Project CERA-2

• collaboration:
  - Potsdam-Institut für Klimafolgenforschung (PIK, Potsdam)
  - Deutsches Klimarechenzentrum (DKRZ, Hamburg)
  - Alfred-Wegener-Institut für Polar- und Meeresforschung (AWI, Bremerhaven)
  - Forschungszentrum Karlsruhe (initially; FZK, Karlsruhe)
• very different data structures
• workshop in WWW: description and discussion of developers
• draft - implementation - further planning (modules)
• split of CERA into a core part (CERA Core = 58 tables) and modules for certain installations and local extensions - diagram

The CERA Core

• divided into 8 information blocks (= groups of tables)
• the CERA-2 Blocks: for coverage, quality, status, access (e.g.) - diagram
• the CERA-2 tables: 11 relations, 9 LOVs - diagram
• 22 lists of values (LOVs) to facilitate the input by pull down menues

The CERA Modules

• module DATA_ORGANIZATION - diagram
  describing the structure, by that the data reference the four dimensional spacetime (e.g. description of axises)
• module DATA_ACCESS - diagram
  informations for automated access

Installation

• DDL-SQL and SQL-tools in WWW
• loading layer
• ORACLE Forms surfaces for: read, load, update
• CERA-2 running at PIK - diagram
• open development (modules)
• tools for normalized data export (NASA-DIF, FGDC-CSDGM) in preparation

Use of CERA-2 for Hydrological Meta Data

• especially adapted to handle spatial meta data ...
• ... about physical measurements (waterlevel, discharge)
• ... of very different storage formats
• quality information is kept (FGDC): accuracy, consistency, completeness, horiz. & vertical accuracy
• extensible: individually for single sites (local extensions) and for groups of institutions (modules)
• existing data (files, DBMS) can be integrated

Further Information

• CERA-2 Central Page: http://www.pik-potsdam.de/dept/dc/e/sdm/cera/
• DKRZ Technical Report No. 15 (Lautenschlager, Toussaint, Reinke; paper and web-version)
• CERA-2 - ein raumbezogenes Daten- und Metadatenmodell (Toussaint, Lautenschlager, Reinke); in Ralf Kramer & Friedel Hosenfeld (eds.): Heterogene, aktive Umweltdatenbanken; GI-Workshop Vilm 1998, Metropolis-Verlag, Marburg 1999