[Css-csts] RE: ASN.1 Reference

[John Pietras]

Yves and Martin,

According to the ASN.1 spec that Yves sent to me, the ModuleIdentifier (section 12.1) is constructed as:

ModuleIdentifier ::=

modulereference

DefinitiveIdentifier

 

where "modulereference" ( section 11.5) is defined as having the same format as "typereference" (section 11.3), which is defined as 

"A "typereference" shall consist of an arbitrary number (one or more) of letters, digits, and hyphens. The initial

character shall be an upper-case letter. A hyphen shall not be the last character. A hyphen shall not be immediately

followed by another hyphen." [the italics are mine, for emphasis]

 

In the SLE and CSTS specifications, our modulereference elements have all capital letters, not just an initial cap as required by the 

modulereference definition. Is that a special CCSDS convention, and if so is it written down anywhere? If it's not already written down, 

should we make the constraint that the characters of a modulereference be all upper case  part of the CSTS conventions,

as part of the Guidelines? 

 

On a different topic, by my reading of the ASN.1 specification, many of the identifiers that are typed as 

ObjectIdentifierType ( "OBJECT IDENTIFIER" - section 31) in the ASN.1 modules of the SLE and CSTS FW specifications are more 

properly "relative OIDs" that could (should?) be of type RelativeOIDType ("RELATIVE-OID" - section 32). Should the Guidelines

allow what are really really relative OIDs to be specified as:

- ObjectIdentifierType or RelativeOIDType, with no preference;

- ObjectIdentifierType or RelativeOIDType, with a preference for ObjectIdentiferType for consistency with the CSTS FW;

- ObjectIdentifierType or RelativeOIDType, with a preference for RelativeOIDType because the ASN.1 spec has that type for exactly this purpose;

- ObjectIdentifierType only, for consistency with the CSTS FW; or

- RelativeOIDType only, because the ASN.1 spec has that type for exactly this purpose?

 

Is there any reason that the RelativeOIDType is not used in the SLE or CSTS FW? Is is somethig that was created after the first SLE specs were 

written? Since the ASN.1 compilers seem to work with these defined as OBJECT IDENTIFIERs, I assume that the ObjectIdentifierType 

is valid for what are really relative OIDs.

 

Thanks for any comments and insight that you can provide.

 

Best regards,

John


----- Forwarded Message -----
From: "Yves Doat" <Yves.Doat at esa.int>
To: "john pietras" <john.pietras at gst.com>
Cc: johnpietras at ieee.org
Sent: Friday, May 7, 2010 10:00:18 AM GMT -05:00 US/Canada Eastern
Subject: ASN.1 Reference

Dear John,

Here is the reference of the ASN.1:
Information Technology—Abstract Syntax Notation One (ASN.1): Specification of
Basic  Notation.   International  Standard,  ISO/IEC  8824-1:2002.   3rd  ed.
Geneva:  ISO, 2002.

Please find attached the final draft of that document (I never got the issued
document). The identifier definition is in section 11.3 and section 31.3
provides the OID definition.

Best regards
Yves
(See attached file: ASN.1 ISO_IEC_FDIS_8824-1 Specification of ASN1 basic
notation.PDF)

 
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