The concept of metadata

GCW Portal metadata are divided in 4 categories which are briefly described in Table 1. Among these 4 categories, data providers or supporting data centres are supposed to provide 3 of them. Further below in this document, there are recommendations on how to provide these.

Table 1: Brief introduction to different types of metadata.





Discovery metadata

Used to find relevant data

Discovery metadata are also called index metadata and are a digital version of the library index card. It describes who did what, where and when, how to access data and potential constraints on the data. It shall also link to further information on the data like site metadata. GCW is required to expose this information through WMO Information System as well. Discovery metadata are thus WIS metadata, although the GCW portal can translate to WIS for those not using WMO standards directly.



Use metadata

Used to understand data found

Use metadata are describing the actual content of a dataset and how it is encoded. The purpose is to enable the user to understand the data without any further communication. It describes content of variables using standardised vocabularies, units of variable, encoding of missing values, map projections etc.

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Configuration metadata

Used to tune portal services for datasets for users.

Configuration metadata are used to improve the services offered through a portal to the user community. This can be e.g. how to best visualise a product. This information is maintained by the GCW portal and is not covered by discovery or use metadata standards.


Site metadata

Used to understand data found

Site metadata are used to describe the context of observational data. It describes the location of an observation, the instrumentation, procedures etc. To a certain extent it overlaps with discovery metadata, but more so it really extends discovery metadata. Site metadata can be used for observation network design.