The <StartDate> element is used to model a <Performance> where the date is known but where the time is undefined. It is up to the Consumer as to how they choose to order <Performance> elements which have a combination of <StartDate> and <StartDateTime>. If possible, Suppliers should utilise <StartDateTime> rather than <StartDate>.
Used to model a situation when the date of a performance is either not known or is thought to happen within a given datespan. This should be only used as a temporary data type if possible and as the information becomes more concrete then the IVES document should be re-supplied with the <StartUndefined> replaced with a <StartDate> or <StartDateTime> as appropriate.