Occurrence Display
An occurrence in Windchill is a database object that stores information about one named usage of a part within a part structure. The name of an occurrence is called a reference designator. For example, the top assembly of an automobile must have a quantity of 4 tires. An occurrence can be created for each use of the part “tire” in the automobile assembly and by assigning a reference designator such as T1, T2, T3, and T4. The occurrences can contain other unique information such as the geometric positioning of the tire image within the image of the automobile assembly. For more information, see Occurrences.
Part occurrences are seen in Structure tab on the information pages of objects having part structures. They are displayed in a table in the Occurrences tab and in the structure pane when the viewing mode has been set to Show Occurrences. For more information on setting the display to view occurrences, see Viewing Action Set - Parts.
Windchill does not require that occurrences be created for every usage of a part within an assembly. For example, a user can create an assembly using a part with quantity of 10 and only provide reference designator names for 5 of the usages. When the part structure is viewed with the display set to Show Occurrences the part structure will show one row for each named occurrence and a summary row marked with the nonoccurrence status indicator 
. Each occurrence row will display the occurrence name in the Reference Designator column and have a quantity of 1. The summary row will show no value in the Reference Designator column and the quantity will be set equal to the total quantity minus the number of occurrences. When new occurrences are defined they will appear in new rows and the quantity in the nonoccurrence summary row will be reduced by the number of new occurrences defined. If the number of new occurrences defined equals or exceeds the total quantity, the quantity is increased to equal the number of defined occurrences and the nonoccurrence summary row disappears.
. Each occurrence row will display the occurrence name in the Reference Designator column and have a quantity of 1. The summary row will show no value in the Reference Designator column and the quantity will be set equal to the total quantity minus the number of occurrences. When new occurrences are defined they will appear in new rows and the quantity in the nonoccurrence summary row will be reduced by the number of new occurrences defined. If the number of new occurrences defined equals or exceeds the total quantity, the quantity is increased to equal the number of defined occurrences and the nonoccurrence summary row disappears.Operations may be performed on individual occurrences and the nonoccurrence summary row. For some operations the results when performed on the summary row will differ from the result when the operation is performed on an occurrence node.
For more information, see Adding Occurrences and Editing in the Occurrences Tab.
Adding Site-Specific Attributes to an Occurrence
To add a site-specific attribute on an occurrence, use the following procedure.
 | You must be a site or organization administrator to complete steps 1 through 3. |
1. From Manage Global Attributes section of the Type and Attribute Management utility, create a reusable attribute for the site-specific attribute that you want to make available for the occurrence. For more information, see Managing Reusable Attributes and Creating Reusable Attributes.
2. In the Manage Types pane of the Type and Attribute Management utility, select the Uses Occurrence Attributes type.
3. On the Attributes tab for the Uses Occurrence Attributes type, create a new attribute, keeping in mind the following:
◦ On the Define Attributes step, select Global for the attribute type.
◦ On the Choose Global Attribute step, select the global attribute that you created for the site-specific attribute in step 1.
For more information, see Creating a New Attribute.
4. Your new attribute will not display in the Occurrences tab until you create a table view that includes the new attribute. For more information, see Customizing Table Views.
