Semantic metadata at any given level does not necessarily comprise a subset of that at any other level.

For example, semantic metadata at the data level provides the information needed to use the data, such as:

• Parameter names; e.g., temperature.
• Units; e.g., degrees Centigrade.
• Missing value parameter; e.g., -99.

While semantic metadata at the directory level provides the information needed to locate data sets, such as:

• Parameter ranges
• Parameter names (note the overlap here)
• Campaign