Editor's note: These minutes have not been edited. SMI Documentation BOF 26 June 1996 at Montreal IETF Chaired by Christian Huitema Reported by Keith McCloghrie The BOF began with an introduction by Christian Huitema, explaining that this BOF was a direct result of the IAB's resolution of the Appeal against the progression of the SNMPv2 SMI as a Draft Internet Standard. Dave Perkins then made a presentation. While some of Dave's presentation was of a tutorial nature, a number of his slides invoked discussion. In particular, it was observed that SNMPv2's SMI is based on the 1987 version of ASN.1 together with an addendum from 1988. This set of documents is no longer available from the normal sources of ISO standards documents. It was agreed that the SMI is an adapted subset of ASN.1, in that ASN.1's rules and the SMI's rules overlap but the latter contains some extensions not allowed in ASN.1. While the macros used in the SMI can't be compiled as ASN.1, the consensus felt that this was irrelevant, since the SMI is not a direct subset of ASN.1, and because their purpose is to document the SMI's syntax rules, not to be compiled. The important question is whether the SMI's syntax rules are made sufficiently clear by RFC 1902-1904. It was observed that these RFCs are the clearest documentation of the SMI to date, and that it is impossible, and potentially undesirable, to make every last detail absolutely clear. The recent use of an INDEX clause with the same object appearing twice with different semantics was cited as an example. Dave questioned whether a MIB-compiler can be written just from the information contained in the RFCs. It was suggested that it could if the compiler is "liberal in what it accepts, conservative in what it expects." The liberal part is easy, but the conservative part is harder. It was observed that a specification of the SMI syntax rules in BNF had been proposed to the SNMPv2 WG during its deliberations, and would have been welcomed, but no actual BNF was submitted prior to (nor since) the WG deadline. During further discussion, the following problems/questions were cited: - does the presence of ASN.1 comments count as whitespace, - forward references are allowed but not supported by some MIB compilers, - hyphens are no longer allowed but exist in many existing MIBs, - can the SMI's reserved keywords be used as descriptors/names, - what is the maximum length of character, hexidecimal and bit strings, - when are IMPORTS statements required, - clarification sought on the use of value notation in DEFVAL clauses, - more explanation needed on identifying MIB modules, - the built-in OSI descriptors should expand to include { itu xx } - just how much "creativity" is allowed with the INDEX clause. - the ASN.1 usage in the definition of the BITS construct is questionable. It was decided that two new documents would be potentially useful: 1. a document to capture those rules used by the SMI, for which the ASN.1 documentation is no longer obtainable, and to provide additional text where the existing RFCs are incomplete. 2. a user's guide to writing MIB compilers. It was agreed that the first of these documents is the more urgent, and that Dave Perkins will write a first draft of it. A number of people will provide review, including Jeff Case and Keith McCloghrie, and that Christian Huitema and Randy Presuhn would review any ASN.1 text. There was consensus that to be useful, the documents should be specific, to the point, and as concise as possible, without explanation/tutorial information. A rough schedule was for Dave Perkins to send the first draft to the SNMPv2 WG mailing-list by the end of July, and to aim to have the document complete by the December IETF meeting.