choiceSelection

indicates whether single or multiple choices can be selected. The attribute choiceSelection can have one of the following values:
- "single" (D) - only a single choice from the list must be selected, usually presented as a radio button
- "multiple" - a single choice or several choices from the list can be selected, usually presented as a checkbox. At least one choice must be selected. All choices selected are processed.
If the multiple choices describe the same variable, the variable must have the attribute valueType "set-string", "set-real" or "set-integer". A set variable can be multi-valued where other types of variables can not. For example, an author can inquire of the end user "Which warning tones were heard?" and provide the choices: "Stall", "Engine fire", "APU Fire", "Unsafe landing". When the user selects one or more of these choices, the values would be added to the set-string variable Warning tones. Global properties can not be set type variables. This is because product attributes and conditions can not be sets.