bilgic@IRO.UMontreal.CA (Murat Bilgic) (03/05/91)
It seems to me when ASN.1 standard has been developed, not too many people paid attention to the possible conflicts between ISO 8824 or X.208 and future encoding rules. For example, according to note 2 of clause 18.4 of ISO 8824, "Encoding rules ensure that the encoding for a sequence value in which a "DEFAULT" or "OPTIONAL" element value is omitted is the same as that for a sequence value of a type in whose type definition the correspon- ding element was omitted. This feature can be useful in defining subsets." According to BER, there is no problem with this statement. However, if someone uses proposed PER, then the above statement is no longer valid. The reasons are pretty obvious: - A component is encoded identifier-implicit only if it is not immediately preceeded by an OPTIONAL or a DEFAULT component, - If the last component in the SEQUENCE is either OPTIONAL or DEFAULT and if it is not present in the value, then a "00" is sent in place of it. Naturally, my question becomes "how binding is the ASN.1 standard on the standards for encoding rules?" In other words, if there is a conflict between two, what happens? The introduction of 8825 does not tell anything about this. Is there any soul out there who has an idea about this? Thanks in advance, Murat Bilgic <murat@davinci.concordia.ca> <bilgic@iro.umontreal.ca>