questions about entities and entity declarations

Questions about entity structure and entity declarations.

* should XML require all entities to be synchronous with the document's
logical structure?

* should XML restrict the types of entities?  We seem to agree to
keep document entities, text entities, and non-SGML data entities, and
to drop subdocument entities, so this boils down to
  * whether XML should keep or discard the concepts of CDATA and
    SDATA entities (6.1).
  * whether XML should retain 'data text' entities (CDATA,
    SDATA, PI) (10.5.3, 8.1)
  * whether XML should retain 'bracketed text' entities (STARTTAG,
    ENDTAG, MS, MD) (10.5.4)

* should XML prescribe the use of an ENTITY-END character as the
canonical method of handling entity boundaries, as a way of simplifying
exposition and implementation (6.2.2)?

* should XML retain or relax SGML's prohibition on ENTITY attributes
referring to SGML text entities (

* if XML makes DTDs optional and allows partial DTDs, what must or may a
parser do when it encounters references to undeclared entities (9.4)?
Should XML declare any set of entities automatically?

* if XML uses ISO 10646, should there be a special form of character
reference using hexadecimal, not decimal, numbers, since most references
to ISO 10646 and Unicode use hex, not decimal (9.5)?

(So references to schwa could take a form like &u0259; or &x0259;, not
*#601;, which is rather error-prone, given that nothing in the Unicode
documentation gives decimal numbers for the character positions.)

* Should XML remove SGML's prohibition on ENTITY attributes for
notations (11.4.1)?