Metadata Syntax

Three forms of metadata are recognised. File metadata is used to describe or override the default syntax for the data file itself. Global metadata has the same purpose as global attributes in a cdf file and describes the file contents collectively. Variable metadata is equivalent to the cdf variable attributes and describes each data product individually.

All header entries take the format
parameter = value
where parameter and value are strings of printable characters. The equals sign may be embedded in space characters, and white space is stripped before the parameter token. Leading and trailing white space is removed from the value token before evaluating it. Where the value token is text it is enclosed in double quotes, in which case white space is valid within the value string.

The value token can take three forms, a single data value (which may be quoted text), a comma delimited sequence of data values or the name of a data variable in the same file carrying the requisite information. The simplest of these options that is sufficient to describe the quantity (or quantities) should always be used. A metadata variable should only be used if the metadata itself requires further metadata to describe it, or its value is record varying.

Multiple value's may be continued onto more than one line by using `$\backslash$' as a continuation marker after a comma in a separated list of values. All text beyond the `$\backslash$' is ignored and the next line is concatenated. Continuation markers may NOT be used within a quoted text string as they will be treated verbatim as part of the string.

Any file metadata should appear before global or variable metadata blocks as they affect the reading of subsequent input. Variable metadata blocks must appear in the same order as the variables appear in the data records. There is no preferred order for the global metadata blocks, nor parameters within any metadata block.