Re: Where is the OID "dot convention" spelled out?

See RFC 1778, 2.15:
   Values of type objectIdentifierSyntax are encoded according to the  
   following BNF:
   
     <oid> ::= <descr> | <descr> '.' <numericoid> | <numericoid>
   
     <descr> ::= <keystring>

     <numericoid> ::= <numericstring> | <numericstring> '.' <numericoid>
   
   In the above BNF, <descr> is the syntactic representation of an
   object descriptor. When encoding values of type
   objectIdentifierSyntax, the first encoding option should be used in 
   preference to the second, which should be used in preference to the
   third wherever possible. That is, in encoding object identifiers,
   object descriptors (where assigned and known by the implementation)
   should be used in preference to numeric oids to the greatest extent
   possible. For example, in encoding the object identifier representing
   an organizationName, the descriptor "organizationName" is preferable
   to "ds.4.10", which is in turn preferable to the string "2.5.4.10".

This was refined in RFC 2252, 4.1.  In particular, it eliminates
 the "ds.4.10" form.