Main Changes from CEF version 1

Summarised below are the main changes from the previous cef specification (which we shall denote CEF-1.0) and CEF-2.0. Software tools should consult the File Metadata parameter FILE_FORMAT_VERSION which is required from CEF-2.0 onwards.

• Files require a File Metadata entry FILE_FORMAT_VERSION to specify the version of CEF to which it complies. Note that CEF-2.x is NOT backward compatible with CEF-1.0.
• Generally the specification is more rigid/prescriptive
• Times can be given to arbitrary accuracy (though this does not guarantee that software tools will be able to retain arbitrary accuracy without due care and attention).
• INT data type has been added
• The time data type has been changed to ISO_TIME
• For time DELTA_PLUS and DELTA_MINUS variables are measured in seconds, not milliseconds.
• Text metadata and data are enclosed in double quotation marks.
• Within metadata comma-separated lists line continuation markers (`$\backslash$') have been introduced
• All keywords and enumerated types have been defined as case insensitive (and have been formatted in this document in capitals).
• Metadata names have been modified and added to be compatible with the Cluster Active Archive Metadata Dictionary. This activity is ongoing.
• Array-handling metadata syntax (e.g., LABLAXIS, LABEL_i, DEPEND_i, DELTA_PLUS, DELTA_MINUS, and others) has been modified.
• All metadata can take one of: a single value, a comma-separated list of values, or the name of a variable.
• Headers are required to be attached, but an INCLUDE parameter has been introduced to read in metadata from another file.
• Start_data has been replaced by DATA_UNTIL with an optional text value which corresponds to the text starting the last line of the file.