DOCTYPE

You can edit the document type declaration to change its name, but
the name must always be the same as the name of the root element. Changing
the name in the document type declaration or the root element automatically
changes the name in the other.

SYSTEM, PUBLIC

Select System to enter an external identifier pointing to
a DTD, for example http://www.acme.com/dtds/basic.dtd.
Select Public to include a public identifier that can be used by
an XML processor to generate an alternative URI. The public identifier
must be typed in the first enabled edit box in the dialog box. If
an alternative URI cannot be generated, the URI provided in the
system identifier is used. External identifiers without a public identifier
are preceded by the keyword SYSTEM. External identifiers with a public
identifier are preceded by the keyword PUBLIC.

(No label)

Use the edit box to enter an internal DTD subset. If you supply both
external and internal subsets, entity and attribute-list declarations
in the internal subset take precedence over those in the external
subset.