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To clarify:
- Component: a schema component is one of the things a schema author writes in a schema.
- Component Instance: a schema component instance is the non-shared instance of a sharable schema component, that is, in its usage context.
- For example: a global type definition must be referenced from an element to be used. The type as it appears in the context of that element is called an 'instance' of that schema component.
- Occurrence: in data, and the infoset, the data corresponding to a schema element declaration is called an 'occurrence' of the element. (Not to be confused with 'instance')
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- Note however, that we may need attributes. E.g., to refer to the maxOccurs attribute of a specific element declaration we would write e1/@maxOccurs
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