mandatory / repeatable

In the DCTAP model, the expected cardinality of a property can be expressed with the elements mandatory and repeatable. These elements take Boolean values that express “true” or “false” in one of two supported ways:

• The keywords true and false (case-insensitive).

• The integers 0 and 1.

These supported Boolean values are handled in the following ways:

• normalized as the Boolean class instances True and False in the internal Python object.

• normalized as true and false in the JSON and YAML outputs,

• displayed as True and False in the compact text output.

Note that empty values (ie, strings of length zero) are simply interpreted as unspecified and are not assigned an explicit Boolean value.

propertyID	mandatory	repeatable
dc:creator	1	0
dc:date	0

This is interpreted as:

DCTAP instance
    Shape
        shapeID                  default
        Statement Template
            propertyID           dc:creator
            mandatory            True
            repeatable           False
        Statement Template
            propertyID           dc:date
            mandatory            False

Any other value for either element — including an empty string for when the element is present but left blank — has no effect on the default of None for each element and will be passed through as a string (or empty string) to the JSON and YAML output.

An empty string value will result in an element not being displayed at all in the compact text output; in the verbose text format, the value will be displayed as the default “None”.

propertyID	mandatory	repeatable
dc:creator		N
dc:date	Y

This is displayed as:

DCTAP instance
    Shape
        shapeID                  default
        Statement Template
            propertyID           dc:creator
            repeatable           N
        Statement Template
            propertyID           dc:date
            mandatory            Y

WARNING [default/repeatable] 'N' is not a supported Boolean value.
WARNING [default/mandatory] 'Y' is not a supported Boolean value.

The four possible combinations of mandatory with repeatable translate into the following minimum and maximum values when cardinality is expressed as a range (where “-1” means “many”).

mandatory/repeatable		min/max
mand	repeat	min	max
False	False	0	1
True	False	1	1
False	True	0	-1
True	True	1	-1

Users of DCTAP in areas such as biology, where more expressive cardinality is required, may want to extend the model with such ranges.