Developing Uniform Services to Access

UNIDART

Developing uniform services to access

data and product from meteorological centres

Jürgen Seib

Deutscher Wetterdienst

The Uniform Data Request Interface Programme, UNIDART, is aimed at the development of uniform services to access meteorological data and products. For this purpose, the data and products are classified into data categories such that a uniform request form can be defined for each category. Examples for data categories are climate time series or forecasts. A service is implemented for each data category. The service accepts a request compliant to the appropriate form, performs the request, and produces the response document. Now, a meteorological data centre which maintains a data resource of a category is able to support access to this data resource by running the according UNIDART service at his site.

A user will interact with the services via a Web portal. The portal provides a user-friendly interface to specify a data request. The request is then submitted to the corresponding UNIDART service at a meteorological data centre. The service produces the response document which is delivered back to the portal where it is either displayed to the user or stored for a download.

The uniform services will overcome data access and exchange problems which are caused by the heterogeneity of data sources in the meteorological data centres. Consider, for example, the access to climate data. Since several years, relational databases are used in the meteorological data centres to store climate data. However, a standardised data model for climate databases does not exist. Therefore, most climate databases are different. They have various tables with miscellaneous names of tables and columns. They differ in structure, implementation and storage. This makes it impossible for an external user to query a climate database directly. Apart from that fact additional problems may concern security and authorisation issues.

The UNIDART services are implemented as so-called Data Grid services based on the OGSA-DAI[1] software. A Data Grid service is a special Web service which supports the exposure of data resources, such as relational databases or XML databases, and which has a focus on a safe, secure and confidential communication and transfer of data. Authentication, authorisation, and encryption are inherent features of the grid service technology.

Currently, UNIDART services exist for climate time series and forecasts. They were installed at several national meteorological centres. A prototype Web interface for the interactive use of the two services has been developed. This interface is part of a prototype implementation of a Global Information System Centre (GISC) portal (see However, UNIDART services are independent. A service which runs at a provider site could be also contacted from other Web portals. This makes UNIDART attractive for a use within WIS. UNIDART services can be adopted to realise a pull mechanism from a GISC to DCPCs or NCs. A user would logon to a GISC portal to formulate a data request. In the case where the requested data is not located at the GISC the request will be submitted to a centre that provides this data.

[1] Open Grid Services Architecture - Data access and Integration