Reference_Syntax.mark = “once | none | global | dataref”
• once (default)The node representing the enclosing object binds to a node in the Data model in accordance with the standard matching rules.
• The node representing the enclosing object is transient. It will not be bound to any node in the Data model.
• The containing field is global. If the normal matching rules fail to provide a match for it, the data-binding process looks outside the current record for data to bind to the field.
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