enag@ifi.uio.no (Erik Naggum) (10/23/90)
Hi. I recently started to look into ASN.1 at the detail level (as opposed to a more general view previously). Based on my careful reading of Blue Book X.208/9, there are several smallish things I wonder about. 1. In the ASN.1 SubTypeSpec production, the character `|' separates the elements in the SubTypeValueList. However, `|' is not in the ASN.1 character set as defined earlier in the spec. It is defined to be "new" in the Macro Notation. How serious is this? Does it mean that subtypes are so new compilers and implementations don't support them? Does it mean ISO 8824 differs from X.208? The Externaltypereference and Externalvaluereference productions early in the spec lack a `.' between the modulreference and the type- and valuereference, respectively. The summary at the end has it right. Annoying. 2. In the BER, the floating point format is rather peculiar. I've heard that IBM 360/370 uses base 16 exponents, and that this is the sole reason for supporting the F bits. Why not use the IEEE stan- dard? And why is there no more than a pointer to ISO 6093 for the decimal format? Getting ISO 6093 takes weeks around here, and costs a hell of a lot of money. Can anybody tell me, briefly, what the essential characteristics of the three Number Representations are, and the respective merits of each? 3. The purpose of the ObjectDescriptor "useful type" is not clear to me. When is it used? Other than that, the specs are pretty readable as is, once I could devote a whole morning to reading them. (How to get time to read specs in one sitting: Work so hard your body can't fight a common cold, and read it in bed. :-) Thanks for your replies. -- [Erik Naggum] Naggum Software; Gaustadalleen 21; 0371 OSLO; NORWAY I disclaim, <erik@naggum.uu.no>, <enag@ifi.uio.no> therefore I post. +47-295-8622, +47-256-7822, (fax) +47-260-4427 --