Bruno, Thanks for the reference to John Larmouth's tutorial, which I had forgotten about. My interpretation of your response is that the elements in question will be implicitly tagged with their universal tags. Slide 13 implies this, too. I posed the question because I was confused by the following statement in John's book: <quote> With an environment of implicit tagging, all tags are applied as implicit tagging unless one (or both) of the following apply: · The tag is being applied to a "CHOICE" type-notation or to a type-reference-name for such notation; or · The keyword "EXPLICIT" follows the tag notation. </quote> "The tag is being applied to" seems to mean a user-defined tag (i.e., a tag surrounded by square brackets). Frank > -----Original Message----- > From: Konik, Bruno [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, October 04, 2000 12:36 PM > To: '[EMAIL PROTECTED]' > Subject: RE: [ASN.1] Tagging of CHOICE Elements for Which User-Defined > Tag s are Not Sp ecified > > > Franck, > I have forgotten to tell you about John Larmouth's tutorial > about tagging > (http://www.larmouth.demon.co.uk/tutorials/tagging); which is > really very interesting. > (thank you John Larmouth!) > > > > ---------- > > De : Konik, Bruno > > R> épondre à : [EMAIL PROTECTED] > > Date : mercredi 4 octobre 2000 17:34 > > A : '[EMAIL PROTECTED]' > > Objet : RE: [ASN.1] Tagging of CHOICE Elements for > Which User-Defined Tag s are Not Sp ecified > > > > Franck, > > > > in an IMPLICIT TAGGING mode (like yours since it is > "FOO DEFINITIONS IMPLICIT TAGS ::="), there is no automatic > tagging of the elements and there is no need to tag your > elements since the are different universal type. If the > universal types were the same then they should be tagged by > the syntax specifier; if not, the decoder couldn't know what > element it receives. > > In an AUTOMATIC TAGGING mode (which is recommended by > X680) they would be automatically tagged (by the encoder) and > the specifier wouldn't have to worry about! > > > > I can suggest you to read either John Larmouth's book > (http://www.oss.com/asn1/larmouth.htm) or Olivier Dubuisson's > book (http://www.oss.com/asn1/booksintro.html) about this subject. > > > > > ---------- > > > De : Frank Balluffi[SMTP:[EMAIL PROTECTED]] > > > R> épondre à : [EMAIL PROTECTED] > > > Date : mercredi 4 octobre 2000 15:24 > > > A : '[EMAIL PROTECTED]' > > > Objet : [ASN.1] Tagging of CHOICE Elements for Which > User-Defined Tags are Not Sp ecified > > > > > > I am confused about the tagging of CHOICE elements for > which user-defined > > > tags are not specified. > > > > > > It is my understanding that in an environment of implicit > tagging, a > > > user-defined tag for a CHOICE element must be EXPLICIT: > > > > > yes if it is not then the compiler should issue an error > (at least a warning to say it has transformed the IMPLICIT to > EXPLICIT!) > > > > > FOO DEFINITIONS IMPLICIT TAGS ::= > > > BEGIN > > > > > > Sequence ::= SEQUENCE > > > { > > > utf8String [0] IMPLICIT UTF8String OPTIONAL, > > > -- choice must be explicitly tagged. > > > choice [1] EXPLICIT Choice OPTIONAL > > > } > > > > > > Choice ::= CHOICE > > > { > > > printableString PrintableString, > > > integer INTEGER > > > } > > > > > > END > > > > > > and if the EXPLICIT keyword is not specified for the > element choice (above), > > > the element will be "implicitly" (sorry for the choice of > word) tagged > > > EXPLICIT. > > > > > > What happens if user-defined tags are not specified? In > the following > > > example, is the element choice implicitly tagged: > > > > > > FOO DEFINITIONS IMPLICIT TAGS ::= > > > BEGIN > > > > > > Sequence ::= SEQUENCE > > > { > > > utf8String UTF8String OPTIONAL, > > > choice Choice OPTIONAL > > > } > > > > > > Choice ::= CHOICE > > > { > > > printableString PrintableString, > > > integer INTEGER > > > } > > > > > > END > > > > > > Thanks. > > > > > > Frank > > > > > >
