Special Data Values

As much as possible SokweDB utilizes a controlled vocabulary within the system’s data store. To provide the system’s users[1] with control over the codes used, this vocabulary may be tailored by adding or deleting codes to or from the tables which define the system’s vocabulary.

At times, SokweDB recognizes that particular codes have special meanings, for example, the BIOGRAPHY_DATA table’s F (female) Sex code. The meaning of these codes is fixed into the logic of the system. As examples, an individual must be female to be allowed to have a menstruation, or, the individual must be in the community to be sighted in the community. Some of these codes, like sex, are not defined in tables, they are hardcoded into the system. Others are defined in support or other tables. Because these codes have intrinsic meaning, they cannot be removed from the SokweDB system nor should their presence in the data be used to code a different meaning from that which the code presently has. For example, the meaning of DEPARTTYPES code value O (alive[2]) should not be changed to mean “death due to meteorite impact” because the system’s programs would then allow individuals to have sexual cycles after death. Each of the “special” values that the system requires retain particular meaning is listed in the Special Values section of the code table’s documentation. For further information on the meaning of the “special” values, see the description of the table(s) that contain the code values. Should the meaning of one of these “special” values need to be changed, the logic in the SokweDB programs should be adjusted to reflect the change.

SokweDB prevents ordinary users from altering rows that give meaning to special values in an attempt to prevent mis-configuration of the system. Only users with permissions to modify a table’s triggers may alter the table’s special values.[3] This is not a panacea. To return to the example above, not only does the system expect a DEPARTTYPES code of O to mean alive, it also expects O to be the only code in DEPARTTYPES that means alive. If another DEPARTTYPES code is created to indicate a more specific sort of “alive-ness”, unless re-programmed the system will consider all individuals given that code to be dead, not alive. A careful review of the documentation should be undertaken before modifying the content of tables that instantiate special values.

Footnotes

[1]

As opposed to the system’s programmers.

[2]

Specifically, “still alive and present as of the last census date”.

[3]

Rather than create another role just to control the alteration of special values the choice was made to use PostgreSQL’s TRIGGER privilege. This allows superusers (or the somewhat less privileged) the necessary access. This conveniently separates regular users from those who can do more.

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