Field	Description	Type	Null	Key	Default
id	sequential ID	int(10) unsigned	NO	PRI	NULL
iid	item.id of the referenced item	int(11)	NO	MUL	0
uid	channel.channel_id of the owner of this data	int(11)	NO	MUL	0
sid	an additional identifier to attach or link to the referenced item (often used to store a message_id from another system in order to suppress duplicates)	char(191)	NO	MUL
service	the name or description of the service which generated this identifier	char(191)	NO	MUL