The timestamp attributes enable Suppliers to define when information in an IVES document was created or updated. The values are not intended for display by a Consumer, but rather as suggestions as to the caching and updating of the information by the Consumer.
The values should represent the state of the information in the element and all of the immediate children of the element. They are therefore only set on top-level elements that are contained directly within an <IvesMessage>. If a timestamped element contains a reference to another shared object (eg an <Event> containing a <DescriptionReference> to a shared <DescriptionDefinition>) and the shared element is updated then only the timestamp on the shared element would need to be updated, not the timestamp on all the elements that contain references to it.
If a Consumer middleMan receives an IVES document from a Producer originalSupplier that contains timestamp information, then this information should be discarded if the information is resent from middleMan to a new Consumer finalRecipient. The IVES document that middleMan produces for finalRecipient should contain the creationTime when middleMan first received the document, and if the document has been updated by them (either explicitly and directly or by receiving further update information from 3rd parties) then the lastUpdateTime should reflect this time.