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(b) keeping of backup copies 
(c) protection of data against physical aging of storage media 
(d) continual conversion of data in line with technical innovation, e.g. replacement of outdated 
reading technology 
(e) protection against unauthorized access 
Metadata 
This concerns the documentation of data-related information on measuring techniques, 
equipment, calibration methods, instrument support frames, instrument installation, measuring 
environment etc. 
Apart from the acquisition of the data themselves and their quality assurance, archiving and 
dissemination, also the collection, updating and provision of metadata, i.e. additional 
information on other data, is of enormous importance, especially if the data are to be used for 
climatological purposes. Several organizations have developed metadata concepts and 
information systems, for example INFOCLIMATE which has been developed by WMO. 
With respect to marine meteorological data, information on shipboard measuring equipment 
and on the support frames used is recorded in compliance with the WMO standard. The 
metadata base is maintained in an international context (WMO). For the historical marine data 
stored at the German Weather Service DWD, a comprehensive metadata base is under 
construction taking into account particularly the fast technological progress in shipbuilding 
during the first half of the 20 th century and, consequently, the changing measuring environment 
of maritime data. 
Retrieval methods 
Owing to the use of relational data base methods, a detailed retrieval of data is possible 
enabling inquiries to be processed quickly and data and information to be provided without 
delay. It is also warranted that the archiving methods used continue to be compatible with 
technical developments in the storage and exchange of media. 
Data delivery and exchange mechanisms 
Data delivery and exchange are essential functions of data management. Care has to be taken 
that the real-time data are fed into the Global Telecommunication System without delay and 
are made available to all participants. In the non-real-time mode, mechanisms must be 
provided which ensure a rapid, comprehensive collection of the observation and measuring 
data. For the data from Voluntary Observing Ships, two global centres have been established - 
one of them at DWD, which collect all internationally available shipboard weather observation 
data. 
The data are subjected to a quality check and transmitted to eight regional subcentres, one of 
which is located at DWD. This is done using agreed standards and formats. Likewise, the 
Global Precipitation Climatology Centre operated by DWD provides world-wide precipitation 
data and analyses applying agreed quality standards. 
Climate information systems 
As the Internet developed into the World Wide Web (WWW), this opened up possibilities of 
global, direct access to information on data/products and to the data/products themselves. 
The WWW not only provides the benefit of direct access to data at the producer’s website but