Specialized Administration > Tailoring Business Objects > Object Initialization Rules Administration > Working with Object Initialization Rules > Merging Rules to Create a Composite Rule > The Use of Object Type Hierarchy in Rules
  
The Use of Object Type Hierarchy in Rules
Every rule that is defined specifies the object type for which the rule applies. Object types have their own hierarchy. This hierarchy is used when determining which rules apply to an object. The object type hierarchy defines the top-level type as the parent type and then any subtypes of the parent are children of the parent.
The object initialization rules use this parent-child relationship to identify the rule set that applies to a specific object:
Any rule defined using the parent type also applies to the children of that parent. For example, assume the following:
There is a type named wt.doc.WTDocument that is a parent type.
There are multiple subtypes of WTDocument that are available (such as the two subtypes identified as com.ptc.General and com.ptc.ReferenceDocument).
Then the rules set for the wt.doc.WTDocument object type also applies to objects associated with the subtypes com.ptc.General and com.ptc.ReferenceDocument.
Rules defined for a subtype only apply to that subtype and any children of that subtype. They do not apply to the parent type. For example, a rule defined for the com.ptc.General subtype of wt.doc.WTDocument does not apply to objects that are associated with the wt.doc.WTDocument object type.
If there are rules set for a subtype that affect the same attributes as rules that are set for the parent type, then the subtype rules usually takes precedence. Exceptions include:
when the final argument is included in the parent rule
when the ignore argument is included in the child rule
when a parent rule exists in the current context and a child rule exists in a higher context