[ASN1] ANY DEFINED BY Questions

[Dominic Steinitz]

RFC 3281 defines Attribute as follows.

         Attribute ::= SEQUENCE {
                  type      AttributeType,
                  values    SET OF AttributeValue
                    -- at least one value is required
            }

            AttributeType ::= OBJECT IDENTIFIER

            AttributeValue ::= ANY DEFINED BY AttributeType

1. I thought that ANY DEFINED BY had to refer to an the identifier of a 
NamedType (::= identifier Type). Can it refer to a Type?

2. Should the definition be as follows?

  Attribute ::= SEQUENCE {
      type   AttributeType,
      values SET OF ANY DEFINED BY type,
      -- at least one value is required
      }

3. Is this valid or does the referenced identifier have to appear before it is 
used?

   Foo ::= SEQUENCE {
      bar ANY DEFINED BY type,
      foo INTEGER,
      type OBJECT IDENTIFIER
      }

4. I assume this is invalid but asnp (http://asn1.elibel.tm.fr/tools/asnp) and 
asn1c (http://lionet.info/asn1c/asn1c.cgi) accept it.

   Bar ::= SEQUENCE {
      bar ANY DEFINED BY type,
      foo INTEGER
      }

Thanks, Dominic.

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