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# CFXMLExternalID

Contains the system and public IDs for an external entity reference.

```
struct CFXMLExternalID
```

## Overview

This structure is part of the definition of the [`CFXMLDocumentTypeInfo`](/documentation/CoreFoundation/CFXMLDocumentTypeInfo), [`CFXMLNotationInfo`](/documentation/CoreFoundation/CFXMLNotationInfo), and [`CFXMLEntityInfo`](/documentation/CoreFoundation/CFXMLEntityInfo) structures.

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