Keywords

The keyword section contains declarations of all keywords present in records belonging to the series. Each keyword description consist of "Keyword:" followed by a comma separated list of attributes describing the keyword. Tab or newline characters are ignored. If the keyword is a simple value this takes the following form:

Keyword: <name>, <datatype>, <scope>, <default value>, <format>, <unit>, <comment>

where

<name> is a string specifying the name of the keyword.

<scope> can take the value fixed which means that the keyword has the same value for all data records, or <scope> can take the value variable which means that the keyword does not have the same value for all data records.

<datatype> specifies the data type of the keyword value. The following types are recognized: char, short, int, long, long long, float, double, datetime, timestamp and string.

<default value> is the default value assigned to this keyword. Default is zero for numerical types, the empty string for string types and "1970-01-01 00:00:00" for date and time types. A fixed keyword has the default value for all records.

<format> is a format string as used by the printf family of functions for formatting an object of type <datatype>.

<unit> is a string specifying the physical unit of the keyword value.

<comment> is a string describing the meaning of the keyword.

For example, to declare a keyword containing a floating point value describing velocity associated with a data record, the keyword section would contain a line like

Keyword: "v", float, variable, 0.0f, "%12g", "m/s", "velocity", 0

A keyword can also be a link pointing to a keyword in a record from a different series, hereby making it possible for data records to inherit keyword values from each other. A link keyword has <datatype> equal to link and takes the form the form

Keyword: <name>, link, <linkname>, <target keyword>

where

<name> is a string specifying the name of the keyword.

<linkname> specifies the name of the link, which must be defined elsewhere in the same JSD.

<target keyword> specifies the name of the target from from which to get the value in the record pointed to by the link.

For example:

Keyword: Tilt, link, HMI_ORBIT, P_Angle

This definition means that to get the value of the keyword Tilt, follow the link named HMI_ORBIT to the data record it points to and get the value of keyword named P_Angle from that data record.

[Should we include MIN, MAX and MISSING values to conform with VO tables?]