TdOPCEventItem can store information about categories, conditions, (vendor) attributes and subconditions which are all event items.

TdEventItem provides has the following properties which have several meanings: 

ID : Integer; 

Name : string; 

IType : Integer; 

Items : TdOPCEventItems; 

For categories: 

ID : Id of the category given from the OPC server 

Name : name of the category 

IType : stores the EventType (tdOPCEventtypes) which belongs to the category 

Items : the assigned vendor attributes of this category 

For conditions: 

ID : not used (position in the list) 

Name : name of the category 

IType : stores the category which belongs to this condition 

Items : stores all assigned subconditions for this condition 

For vendor attributes: 

ID : Id of the attribute given from the OPC Server 

Name : name of the vendor attribute 

IType : stores the condition which belongs to this attribute 

Items : nil (not used) 

For subconditions: 

ID : not used (position in the list) 

Name : name of this subcondition 

IType : stores the condition which belongs to this subcondition 

Items : nil (not used)