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You may want to address fields in components other than the source component. This is because your target component may depend on more than one component in the source object. In such cases, you cannot use different component maps with different source components, and the same target component, because each component map creates a different instance of the target component. Data Mapping Engine expressions allow you to use the dot notation to address fields, other than the source component, in source integration object components—for example, [Component Name.Field Name].
Addressing fields in other components is legal only if the cardinality of the component is less than or equal to one relative to the source component—that is, only if the component can be uniquely identified from the context of the source component without using any qualifiers other than the component name. If a field in a component that is not legally addressable is used in the source expression then it leads to a runtime error to the effect that such a field does not exist. Any component that is an ancestor of the source component in the integration object hierarchy has a relative cardinality of 1 which means it can always be uniquely identified from the source component. Therefore, fields in ancestor components can always be legally addressed.
Sibling components can be uniquely identified from the context of the source component only if they do not occur multiple times—that is have a cardinality of less than or equal to 1. Only such siblings can be legally addressed. Therefore, it is not legal to address repeated sibling components. Components that are descendants of a sibling component can be legally addressed only if there is no repeated component in the hierarchical path from the sibling component to the component.
Further, components that are descendants of a sibling of some ancestor of a source component can be legally addressed only if there is no multiply-occurring component in the hierarchical path from the sibling-of-ancestor-of-source component to the component.
|Business Processes and Rules: Siebel eBusiness Application Integration Volume IV|