- From: Ron Daniel, Jr. <rdaniel@lanl.gov>
- Date: Fri, 09 May 1997 10:08:42 -0600
- To: Sukanta Ganguly <SGANGULY@novell.com>
- Cc: w3c-dist-auth@w3.org, urn-ietf@bunyip.com
At 08:54 AM 5/9/97 -0600, Sukanta Ganguly wrote: >Hi, > I wanted to mention some things about the rfc 2141 that I found confusing. You should bring these questions up on the URN-WG list, not the Web DAV list. The URN list is urn-ietf@bunyip.com. I have added it to the CC list on this reply. >The syntax for a URN is specified as ><URN> ::= "urn:" <NID> ":" <NSS> >and NSS also has ":" as a characters recognized within the <others> rule. >Based on this > URN:foo:: -> Is this a valid URN ?? That will depend on the rules for the namespace foo. The URN syntax is an attempt to be as liberal as possible so as to allow many different namespaces to exist. The rules for particular namespaces are intended to be much stricter. As an example, take a look at the URN-WG's internet draft on using bibliographic identifiers as URNs. Two of the namespaces in that document (ISBN and ISSN) disallow the use of ':' and many other characters. The third (SICI) has much more liberal rules because SICIs use lots of funny characters. >I feel that is ":" is used as a reserved terminator of a subsection of a >rule then it should not be used in the recognized character sets for the >other sub-sections of the rule. So I would imagine that ":" is not present >as a recognizable character within the <other> rule of NSS subsection. The URN sytnax RFC takes a strong position on the first two occurances of ':'. After that, it is up to particular namespaces how ':' is or is not used. >It just adds an extra amount of parsing effort for the applications to have >this feature in their parsing mechanisms. I don't say that it is impossible >to have it, but as a application developer, it would be a much messy >approach for me to write code that has this feature in it. I hope this not >taken as a negative criticism. No, it is not taken as a negative criticism. However, one of the requirements on URNs was the ability to grandfather legacy naming systems (such as SICIs). If allowing ':' makes it easier to accomodate some naming schemes, then we thought it would be worth some additional implementation difficulty. The additional difficulty seems very small. The first two ':' characters are required, so once one has stripped off the "urn:" prefix and the NID field with its colon, no more special treatment of ':' is required for a general URN parser. You will probably want to use the NID to lookup special parsing rules for the namespace, but that is another story. >I have a similar concern regarding the usage of "%" character within the ><NSS> subsection. This is what the rule resolution says ><NSS> ::= 1*<URN chars> ><URN chars> ::= <trans> | "%" <hex> <hex> ><trans> ::= <upper> | <lower> | <number> | <other> | <reserved> ><reserved> ::= '%" | "/" | "?" | "#" > >Here we observe that > > <NSS> ::= % could be a valid rule according to the rule definition. At >the same time the system has another defination that says wheneever "%" is >used two <hex> characters should be used. > > <NSS> ::=%%12 -> could also be a valid syntax for NSS. > >My suggestion here is to remove "%" from the <reserved> subsection of <NSS> >rules. > >Please let me know if my thinking is along the lines of what the group has >in mind or am I way out of wack. Single occurances of '%' are disallowed. '%' is supposed to ALWAYS mean that the next two characters will be hex digits that are taken to form an octet. >I appreciate your acceptance of my >participation in the group. > >Thank You >Sukanta Ganguly > >>>> Jim Whitehead <ejw@ics.uci.edu> 05/06/97 12:07PM >>> > >Of potential interest to participants of this WG. > >- Jim > >>To: IETF-Announce: ; >>Subject: RFC 2141 on URN Syntax >>Cc: rfc-ed@isi.edu >>Mime-Version: 1.0 >>Date: Mon, 05 May 97 13:53:28 PDT >>Sender:ietf-announce-request@ietf.org >>From: RFC Editor <rfc-ed@isi.edu> >> >> >>A new Request for Comments is now available in online RFC libraries. >> >> >> RFC 2141: >> >> Title: URN Syntax >> Author: R. Moats >> Date: May 1997 >> Mailbox: jayhawk@ds.internic.net >> Pages: 8 >> Characters: 14077 >> Updates/Obsoletes: None >> >> URL: ftp://ds.internic.net/rfc/rfc2141.txt >> >> >>Uniform Resource Names (URNs) are intended to serve as persistent, >>location-independent, resource identifiers. This document sets >>forward the canonical syntax for URNs. A discussion of both existing >>legacy and new namespaces and requirements for URN presentation and >>transmission are presented. Finally, there is a discussion of URN >>equivalence and how to determine it. This document is the product of >>the Uniform Resource Names Working Group of the IETF. >> >>This is now a Proposed Standard Protocol. >> >>This document specifies an Internet standards track protocol for the >>Internet community, and requests discussion and suggestions for >>improvements. Please refer to the current edition of the "Internet >>Official Protocol Standards" (STD 1) for the standardization state and >>status of this protocol. Distribution of this memo is unlimited. >> >>This announcement is sent to the IETF list and the RFC-DIST list. >>Requests to be added to or deleted from the IETF distribution list >>should be sent to IETF-REQUEST@CNRI.RESTON.VA.US. Requests to be >>added to or deleted from the RFC-DIST distribution list should >>be sent to RFC-DIST-REQUEST@ISI.EDU. >> >>Details on obtaining RFCs via FTP or EMAIL may be obtained by sending >>an EMAIL message to rfc-info@ISI.EDU with the message body >>help: ways_to_get_rfcs. For example: >> >> To: rfc-info@ISI.EDU >> Subject: getting rfcs >> >> help: ways_to_get_rfcs >> >>Requests for special distribution should be addressed to either the >>author of the RFC in question, or to admin@DS.INTERNIC.NET. Unless >>specifically noted otherwise on the RFC itself, all RFCs are for >>unlimited distribution. >> >>Submissions for Requests for Comments should be sent to >>RFC-EDITOR@ISI.EDU. Please consult RFC 1543, Instructions to RFC >>Authors, for further information. >> >> >>Joyce K. Reynolds and Mary Kennedy >>USC/Information Sciences Institute >> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Ron Daniel Jr. voice:+1 505 665 0597 Advanced Computing Lab fax:+1 505 665 4939 MS B287 email:rdaniel@lanl.gov Los Alamos National Lab http://www.acl.lanl.gov/~rdaniel Los Alamos, NM, USA, 87545
Received on Friday, 9 May 1997 12:10:24 UTC