- From: Yaron Goland <yarong@microsoft.com>
- Date: Wed, 6 Aug 1997 12:52:18 -0700
- To: "'Dylan Barrell'" <dbarrell@bb.opentext.com>, "'Whelan, Dan'" <dan@filenet.com>, w3c-dist-auth@w3.org
Seems a bit heavy to require discovery even when your just locking a single resource but not totally unreasonable. Yaron > -----Original Message----- > From: Dylan Barrell [SMTP:dbarrell@bb.opentext.com] > Sent: Wednesday, August 06, 1997 12:31 AM > To: 'Whelan, Dan'; 'Dylan Barrell'; w3c-dist-auth@w3.org; Yaron > Goland > Subject: RE: Requirements Open Issues from Orem > > This is the reason for having an arbitrator for multiple resource > locking but not the reason for distinguishing between single and > multiple resource locking. I think WebDAV should always use the > arbitrator (specifying where the arbritrator is located or how it can > be located) with an XML request body (this draft anyway contains > enough XML) containing one or more URIs representing the resources to > be locked. > > Cheers > Dylan > > ---------- > From: Yaron Goland[SMTP:yarong@microsoft.com] > Sent: Dienstag, 5. August 1997 15:01 > To: 'Dylan Barrell'; 'Whelan, Dan'; w3c-dist-auth@w3.org > Subject: RE: Requirements Open Issues from Orem > > It is not a matter of advantage, it is a matter of HTTP's design. HTTP > can only deliver a single message to a single destination. It does not > have multicast or broadcast capabilities. As such without > transactioning > the only way to deliver a message to multiple resources in an atomic > fashion is to have the message delivered through some mechanism other > than HTTP. What the arbitrator does is act as the resource which can > access that out of band mechanism. > > In the case of trying to atomically lock a single resource one can > skip > the out of band mechanism since HTTP does support sending a single > message to a single recipient. > > Yaron > > > -----Original Message----- > > From: Dylan Barrell [SMTP:dbarrell@bb.opentext.com] > > Sent: Tuesday, August 05, 1997 1:30 AM > > To: 'Whelan, Dan'; 'Dylan Barrell'; w3c-dist-auth@w3.org; Yaron > > Goland > > Subject: RE: Requirements Open Issues from Orem > > > > What is the advantage to be gained from distinguishing between a > > single resource (whos arbritrator does not have to be "located") and > > multiple resources (whos arbritrator[s] has to be located first)? > > > > Cheers > > Dylan > > > > ---------- > > From: Yaron Goland[SMTP:yarong@microsoft.com] > > Sent: Montag, 4. August 1997 20:04 > > To: 'Dylan Barrell'; 'Whelan, Dan'; w3c-dist-auth@w3.org > > Subject: RE: Requirements Open Issues from Orem > > > > There is an arbitrator for single resources, the resource itself, it > > is > > kind enough to lock itself on your behalf. > > > > A server could configure itself such that every resource can serve > as > > a > > lock arbitrator for all resources on that server. > > > > Yaron > > > > > -----Original Message----- > > > From: Dylan Barrell [SMTP:dbarrell@bb.opentext.com] > > > Sent: Monday, August 04, 1997 12:52 AM > > > To: 'Whelan, Dan'; w3c-dist-auth@w3.org; Yaron Goland > > > Subject: RE: Requirements Open Issues from Orem > > > > > > Having an arbitrator for locking multiple resources and the server > > for > > > locking single resources is very contrived and doesn't make sense. > > The > > > locking part of the standard is anyway optional (the single axis > of > > > negotiation) so if a server doesn't want to implement it it > doesn't > > > have to but if it does then WebDAV should specify a consistent > > > standard method by which this can be implemented. If you want an > > > arbitrator for locking multiple resources then it should be used > for > > > locking single resources too. > > > > > > Cheers > > > Dylan > > > > > > ---------- > > > From: Yaron Goland[SMTP:yarong@microsoft.com] > > > Sent: Mittwoch, 30. Juli 1997 21:03 > > > To: 'Whelan, Dan'; w3c-dist-auth@w3.org > > > Subject: RE: Requirements Open Issues from Orem > > > > > > I suspect we will end up with a LOCK implementation where you have > > the > > > concept of a LOCK arbitrator who accepts a list of resources to be > > > locked and then locks them on your behalf in an atomic fashion. Of > > > course this means discovering who the lock arbitrator is for all > the > > > involved resources, assuming one arbitrator can cover them all. > > > Alternatively one can discover what arbitrators exist for a > > particular > > > server and what namespaces they cover on that server. Either way, > I > > > suspect most folks will simply lock each resource individually. > > > > > > Yaron > > > > > > > > > > > > > -----Original Message----- > > > > From: Whelan, Dan [SMTP:dan@filenet.com] > > > > Sent: Wednesday, July 23, 1997 10:50 PM > > > > To: w3c-dist-auth@w3.org > > > > Subject: RE: Requirements Open Issues from Orem > > > > > > > > I view the proposal to use containers to implement > multi-resource > > > > locking as > > > > a somewhat clumsy way to satisfy this requirement for a number > of > > > > reasons > > > > including: > > > > > > > > 1. The principal may not be authorized to create a container, or > > to > > > > file a > > > > resource in a container, and hence could not use this > > mechanism > > > to > > > > perform a multi-resource lock even if he was authorized to > > lock > > > > each of > > > > the resources. > > > > > > > > 2. Creating a transient container in order to obtain a > > > multi-resource > > > > lock > > > > is relatively inefficient, requiring O(2N) operations. > > > > > > > > 3. Servers may elect to implement only session based locks or > > short > > > > lived > > > > timer based locks to provide robust services in an otherwise > > > > unreliable > > > > environment. In such cases, a client is just as likely to > > fail > > > to > > > > remove > > > > a transient container as he is to unlock a lock yet the > server > > > has > > > > no > > > > WebDAV sanctioned way of removing these transient > containers. > > > > > > > > I'd prefer to see the LOCK and UNLOCK methods take an ordered > list > > > of > > > > resources > > > > to LOCK or UNLOCK respectively. (I'm not familiar enough with > > HTTP > > > to > > > > know if > > > > the protocol makes passing a list of resources difficult -- > WebDAV > > > has > > > > already addressed > > > > multi-status responses for the COPY, MOVE and DELETE methods) > > > > > > > > Dan > Whelan > > > > FileNet > > > > Corporation > > > > ---------- > > > > From: Judith Slein[SMTP:slein@wrc.xerox.com] > > > > Sent: Monday, July 21, 1997 12:33 PM > > > > To: w3c-dist-auth@w3.org > > > > Subject: Requirements Open Issues from Orem > > > > > > > > A new version of the requirements draft will be > submitted to the > > > > IETF on > > > > Thursday, 7/24. Your comments on these issues discussed > at Orem > > > > will be > > > > helpful. > > > > > > > > ------------ > > > > > > > > Multiple Resource Locking > > > > > > > > As a result of the discussion at Orem, I was asked to > raise the > > > > issue of > > > > atomic locking of multiple resources to the mailing list > one > > > > more time. > > > > > > > > In an informal vote by those present for the discussion, > 9 voted > > > > to keep the > > > > requirement, 4 to remove it. The rest (about 10 others) > did not > > > > vote. > > > > > > > > At the moment, the requirement reads as follows: > > > > > > > > 5.3.1.2. Multi-Resource Locking. It must be possible to > take out > > > > a > > > > lock on multiple resources residing on the same server > in a > > > > single action, > > > > and this locking operation must be atomic across these > > > > resources. > > > > > > > > ("residing on the same server" was added at the request > of the > > > > group at Orem.) > > > > > > > > The rationale for the requirement is to prevent > livelocks. That > > > > is, if the > > > > requirement is not satisfied, it will be possible for 2 > > > > principals to try to > > > > lock the same group of resources, and for neither to get > all the > > > > locks he > > > > needs. Each may end up with only some of the locks he > needs. In > > > > addition, > > > > the requirement is meant to lessen the burden on the > server that > > > > would be > > > > caused by multiple individual lock requests. > > > > > > > > The current locking draft does not satisfy the > requirement. The > > > > difficulty > > > > is that it defines a LOCK method where the request URI > is the > > > > resource to be > > > > locked. If we tried to accommodate multiple URIs by > moving them > > > > into the > > > > body of the request, it is not clear what request URI > would be > > > > appropriate. > > > > > > > > One suggestion was that the user put all the resources > to be > > > > locked into a > > > > container, and then lock the container. The server > would be > > > > required to > > > > treat the lock request as atomic to whatever depth was > > > > requested. > > > > > > > > ------------ > > > > > > > > The requirement concerning EMail transport will stay as > is. > > > > > > > > ------------ > > > > > > > > Internationalization > > > > > > > > The consensus of the group at Orem was that we should > stay away > > > > from issues > > > > around variants, which are not specific to > internationalization > > > > and would > > > > add enormously to the work of WEBDAV. Jim will make > sure that > > > > this position > > > > is acceptable to the area directors. > > > > > > > > The question was raised whether we need to be concerned > about > > > > collation. We > > > > think that we do not -- we do not sort any query result > sets, > > > > and we do not > > > > define greater-than or less-than operators for pattern > matching. > > > > > > > > We think that we need only to insure that any > information > > > > intended for user > > > > comprehension should be expressed in a way that makes it > > > > possible to display > > > > the information in any desired writing system and > language. The > > > > proposed > > > > internationalization requirement is the following: > > > > > > > > "All information intended for user comprehension must be > > > > expressed in one of > > > > the ISO-10646 character sets and must have a language > tag." > > > > > > > > ------------ > > > > > > > > Reservations > > > > > > > > The consensus of the group at Orem was to leave the > reservations > > > > section > > > > separate, as it is now, and to continue to use the same > > > > terminology. The > > > > locking draft will discuss the standard use of the word > > > > "reservation" and > > > > explain how the shared lock satisfies the need for > reservations. > > > > > > > > The language of 5.4.1.1 will change to make it clear > that the > > > > point of > > > > reservations is to inform other users, not the server, > of an > > > > intent to edit. > > > > The new 5.4.1.1 will say: > > > > > > > > "It must be possible for a principal to register with > the server > > > > an intent > > > > to edit a given resource, so that other principals can > discover > > > > who intends > > > > to edit the resource." > > > > > > > > ----------- > > > > > > > > --Judy > > > > > > > > Name: Judith A. Slein > > > > E-Mail: slein@wrc.xerox.com > > > > Phone: (716) 422-5169 > > > > Fax: (716) 265-7133 > > > > > > > > Xerox Corporation > > > > Mail Stop 105-50C > > > > 800 Phillips Road > > > > Webster, NY 14580 > > > > > > > > > > > > > > > > > > > >
Received on Wednesday, 6 August 1997 15:52:48 UTC