What does <! ... !> mean in XML?

Question

What does <! ... !> mean in XML?

This <? ... ?> specifies a processing instruction according to this, but I found no information regarding the first one.

Answer 1

<! ... !> is not an XML construct due to the ending !>.

However, the following XML constructs do begin with <!:

• <!-- begins a comment, which ends with -->

• <![CDATA[ begins a CDATA section, which ends with ]]>

• <![INCLUDE[ and <![IGNORE[ begin conditional sections, which end with ]]>.

• <!DOCTYPE begins a document type declaration.

• <!ELEMENT begins an element type declaration.

• <!ATTLIST begins an attribute list declaration.

• <!ENTITY begins an entity declaration.

• <!NOTATION begins a notation declaration.

The ending of each of the above constructions is > unless otherwise mentioned.