The Default Collector
The Default Collector policy identifies the components and required objects for a given object. It does this by looking for specific kinds of associations between the composite object and other objects in the registry.
How the Collector locates the components that are associated with a composite object
To identify the components of a composite object, the collector finds objects that are related to the composite object by an aggregation relationship or a reverse aggregation relationship.
An aggregation relationship is indicated by the presence of an
Composition Using Source Relationship attribute in the composite object. Like a regular Relationship attribute, an aggregated Relationship attribute associates an asset with other objects in the registry. However, an aggregated Relationship attribute additionally indicates that the associated objects are components of the object that contains the aggregated Relationship attribute.
A reverse-aggregation relationship is indicated by a
Composition Using Target Relationship attribute that is present in another registry object and points back to the object on which the collection is being performed. Like a regular Relationship attribute, a reverse-aggregated Relationship attribute also associates an asset with other objects in the registry. However, a reverse-aggregated Relationship attribute additionally indicates that the object that contains the reverse-aggregated attribute is a component of the object at the end of the relationship.
Conceptually, both the aggregated and reverse-aggregated forms of the Relationship attribute establish a parent-child relationship between the object being collected (the parent) and objects that are its components (its children). However, the aggregated form expresses the relationship from the perspective of the parent object (that is, the aggregated Relationship attribute exists in the composite object and identifies the object's components), whereas, the reverse-aggregated form expresses the relationship from the perspective of a child object (that is, the reverse-aggregated Relationship attribute exists in a component object and identifies the composite object to which it belongs). The components that make up a composite object can be identified using aggregated Relationship attributes, reverse-aggregated Relationship attributes or a combination of the two.
Aggregated Relationship attributes are specified during the type definition for a composite object. Reverse-aggregated Relationship attributes are specified during the type definition of a component object.
How the default Collector determines whether a component is shared or nonshared
In the list of components that the Default Collector returns to a handler, a component is marked as shared or nonshared. To determine whether a component is shared or nonshared, the Default Collector checks whether the component is associated with any objects other than the one on which the collection is being performed.
If the component is only associated with the object on which the collection is being performed, the Default Collector marks it as a nonshared object.
If the component is associated with other objects in addition to the one on which the collection is being performed, the Default Collector marks it as a shared object.
How the default Collector locates the required objects that are associated with a composite object
In addition to components, the Default Collector also locates the required objects that are associated with a given object. It does this based on presence of required-object Relationship attributes in the composite object.
Like aggregated and reverse-aggregated Relationship attributes, a required-object Relationship attribute identifies objects that are to be collected. When a composite object contains a required-object Relationship attribute, the Default Collector collects the objects that the attribute references and marks them as required objects in the list that it returns to the handler.
In addition to those required objects that the Default Collector locates based on the required-object Relationship attributes that it finds in a composite object, the collector also returns the following items as required objects:
The Type object associated with the object on which the collection is being performed.
The repository items (that is, supporting documents and other attached files) associated with the object on which the collection is being performed.
Working with default Collector
The Default Collector policy is used by many of the predefined asset types installed with CentraSite. Do not edit, delete, or deactivate this policy.
Important: The Default Collector is triggered by an OnCollect event. The sole purpose of this event is to trigger the collector policy for a given object type. Do not attempt to use the OnCollect event to create additional policies that execute before or after the Default Collector or any other collector policy. Doing this can cause handlers to fail. Only one policy should execute when an OnCollect event occurs and that policy should be the collection policy for the object type on which the OnCollect event occurs.