2.2.2 [XML] Section 3.1, Start-Tags, End-Tags, and Empty-Element Tags

C0008:

The specification states:

 [Definition: An empty-element tag takes a special form:] 
 Tags for Empty Elements[44]   
 EmptyElemTag   ::=   '<' Name (S Attribute)* S? '/>'[WFC: Unique Att Spec]
 Empty-element tags may be used for any element which has no content, whether 
 or not it is declared using the keyword EMPTY. 
 For interoperability, the empty-element tag SHOULD be used, and SHOULD only 
 be used, for elements which are declared EMPTY.

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Empty element tags can be used for any element that has no content, including elements that are not declared by using the EMPTY keyword.