Hi Henri,

the "three dots" that you are referring to are specified in X.681 Amendment 1: "Rules of extensibility". The dots are called an "extension marker" and they are used (in the case of the H.323 series) to demarcate the parts of the ASN.1 elements that were added for a particular version of the specification. So below a marker you will find newer additions to the specification.

Frank

----------------------------------------------------- Frank Derks |Tel +31 35 6893238 | Advanced Development |Fax +31 35 6891030 | Philip Business Communications |P.O. Box 32 | |1200 JD Hilversum | |The Netherlands | ----------------------------------------------------| E-mail: mailto:f.derks@pbc.be.philips.com | WWW: http://www.business-comms.be.philips.com | -----------------------------------------------------

-----Original Message----- From: henri.maenpaa@NOKIA.COM [mailto:henri.maenpaa@NOKIA.COM] Sent: 22 March 1999 10:49 To: ITU-SG16@MAILBAG.INTEL.COM Subject: basic ASN.1 coding question

Hi everyone,

I have a pretty basic/specific question about ASN.1 coding: what's the semantic difference if a particular information element is located above/below the "three dots"-line in an ASN.1 structure?

-Henri Mäenpää