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webdav minutes as text

From: Larry Masinter <masinter@parc.xerox.com>
Date: Fri, 7 Feb 1997 12:39:31 PST
To: w3c-dist-auth@w3.org
Message-Id: <97Feb7.133931pdt."244"@palimpsest.parc.xerox.com>
Del's message seemed to have attached the minutes as uuencoded data,
and the hypermail software archive doesn't cope with that, so here's
my translation of what was sent:

                                WEBDAV Meeting Notes
                                 January 27, 28 1997
                               U.C. Irvine, Irvine CA

          An open meeting was held for those interested in the WEBDAV
          initiative. The meeting was held on the campus of the University
          of California, Irvine. The primary focus of the meeting was to
          review and discuss a proposed draft specification.

          Chair:    Introductions and general remarks.

          Web Collections ..................                   Yaron Goland

               WC presented as a mechanism for giving structured response
               to an HTTP request that is machine readable, without
               breaking older clients. WC is encoded as a set of HTML tags
               with some simple semantics.

          Question: Why HTML? Why not straight up HTTP?
          Answer:   Single message type for both "pure" HTTP and HTML

          Presentation (continued):
               WC data can be
                    1.   referenced - <WCAT rel=foo HREF="anchor">
                    2.   hidden - using HDATA
                    3.   explicit - between <WCDATA> ... </WCDATA> tags

          Comment:  So you will have to encode binary data? This is

          A General Discussion of the Issues Ensues:

          Question: Why not use "webmaps" or "sitemaps"?
          Answer:   WC is the same initiative as "web/site maps". Just the
                    name has changed.

          Question: (Clarification of above question:) So why tinker with
                    the original "webmap" spec?
          Answer:   Spec was inadequate.

          Comment:  This is bad design:
                         1.   WC is a flawed mechanism
                         2.   not good overlap between machine
                              readable/human readable response
          Response: Focus on the object-model. Is it complete? Consistent?
                    Web Collections are just a convenient vehicle for
                    expressing the object model; if there is a better way
                    of expressing the model, we'll use it.

          1Hubub:   A protracted discussion on the merits/folly of using
                    HTML to encode an object model for structured HTTP
                    response ensues.

          Chair:    Moves to discuss the Structured Response Object Model
                    independently of encoding.
          Response: Motion fails. More discussion as above.


          Yaron:    Do we all agree that:
                         1.   we need a well defined Structured Response
                              Object Model and,
                         2.   we should have no dependencies on
                              incomplete/ongoing work in other working
                    [A short discussion period on the above points. Editor
                    senses group general agreement on 1., 2. above,
                    although no official poll is taken.]

          Presentation (continued):
               Hierarchical Collections are presented as a special case of
               Web Collections, used to support FCS or "directory" like

          Light Links (Meta Data) ..............              Jim Whitehead

               Explanation of link structure (source, dest, type) as an
               expression of a binary relation on the cross product
               RESOURCE X RESOURCE.

          Question: Who manages the link "types" (e.g., registration)?
          Answer:   Core link types ("core" to implementing WEBDAV) are
                    defined in the specification. Other "types" owned and
                    managed various groups (e.g., Dublin Core). Namespace
                    convention for link types is schema.(schema.type).
          Response: Take care! Define namespace requirements for links so
                    that WEBDAV complies with the "Schema" work group
                    (Chris Weider, Chair).

          Comment:  Why be non-extensible w.r.t. the link definition? Allow
                    other fields to be added to the core fields (source,
                    dest, type).
          Comment:  PICS is doing meta-data. The authors would be well
                    advised to look at the PICS effort.

               1 -  Shorthand for "unstructured discussion". No disrespect
                    for the group or the Chair is intended.

          Presentation (continued):
               The LINK method is presented.

          Comment:  Method name conflicts with the LINK in HTTP/1.1
          Comment:  Links as presented are inadequate for annotation.


          Question: Are links discoverable/extensible in a robust way? How
                    does the Schema/Method stuff tie in?
          Comment:  Look at PICS namespace registration stuff; it may have
                    good ideas for schema registration.

          Presentation (continued):
               UNLINK method presented.

          Question: Should first rev WEBDAV be dodging
                    notification/transaction issues?
          Comment:  This link model may not be efficient on the wire (Keith
                    will write down his concerns on this issue and submit
                    to the list).

          Presentation (continued):
               The convenience methods GETLINKS, GETLINKVAL and SETLINKVAL
               are presented.

          Question: What identifies a link?
          Answer:   The triple (source, dest, type) is the unique ID.

          Question: Must either source or dest equal the URI of the
                    resource which contains the link?
          Answer:   Yes, the authors (somewhat arbitrarily) decreed that
                    source or dest should equal the URI of the resource
                    where the link resides.
          Response: (Roy) This restriction should be lifted.

          The LINKSEARCH Method ...............                Yaron Goland

               The LINKSEARCH method is briefly presented.

          Comment:  Scoping rules for search are inadequate.
          Comment:  Use "agent" rather than "arbiter".
          Comment:  BNF errors need to be cleaned up.
          Comment:  Interaction between the resource namespace and links
                    (which are defined on resources) can be problematical
                    in a distributes setting.
          Comment:  BNF should be modified to reflect extensible link
          Comment:  Design team is shortsighted due to focus on schedule

                    constraints. Is the team doing its homework? Do the
                    team members understand the issues? Are the team
                    members capable of understanding the logical
                    consequences of their design decisions?


          Locking ......................                       Steve Carter

               The difference between "checkout" (for version control)
               versus "lock" (for document repository) is explained. Lock
               is intended to control resource "collision"; lock is not an
               access control mechanism.

          Question: Why can't lock tokens cross "client space" boundaries?
                    This seems to be an arbitrary decree.

          Comment:  Range locking as described abuses the HTTP/1.1 notion
                    of range. Why not address ranges with teir own URI?
          Comment:  Agrees with comment above. Design team broke its own
                    rule (WEBDAV acts only URI addressable objects). URI
                    addressable ranges more compatible with HTTP
                    philosophy. Also, how do entity tags differ from lock
                    tokens, functionally speaking?

          Comment:  What is WEBDAV locking in the context of highly
                    replicated resources?
          Hubub:    Much discussion over replicated, distributed resources.

          Chair:    Requests that range locking be taken to the discussion
                    list, noting the following outstanding issues:
                         1.   locking highly replicated resources,
                         2.   advisory lock vs. exclusive lock,
                         3.   support for "graceful degradation" of
          Comment:  With respect to above recommendation by chair; the
                    proper forum for resolving design issues in general is
                    on the list. IETF is an open forum.

          Question: What about "orphaned" lock tokens? Spec should say
                    something about the conditions that can lead to lost

                                Special Presentation
                        Email Access to WEBDAV Functionality

          Email & WEBDAV  .................                 Einar Stefferud

               Do not ignore mail transport level! Push vs pull models;
               mail has some pluses:
                    1.   Latency can work for you
                    2.   Administrative functions - mail more autonomous,
                    3.   Mail is mature, tested technology.

               Industry has evolving, Jungian mindset:
                    1.   Computing - no connectivity,
                    2.   Networking - Autonomous homogeneous nodes,
                    3.   Interneteorking - Autonomous heterogeneous nodes,
                    4.   Interworking - Autonomous heterogenous distributed

                                       Day Two

          Version Control ..................                  Jim Whitehead

               Review of "champion" models. Presents the "version tree" as
               conceived by the design team, with "default published
               version" (dpv), "history" links and "version tree handle".

          Comment:  Tree handle and the dpv: if we access the dpv through
                    tree handle for some methods, how do we get to the
                    handle itself?
          Response: Can't use redirect; we get pushback from the Server
                    Config crowd.
          Question: Which methods act on dpv via tree handle? Which do not?
                    Is there consistency here?

          Hubub:    Extended discussion on what version "control" means in
                    a distributed environment.
          Chair:    Directs that a discussion of Version Control in a
                    distributed, replicated environment be established on
                    the list.

          Question: Does the design accommodate "derivitaive" work?

          Question: Where is the definition of "history" in the spec? Also,
                    "history" may itself be a distributed object; does spec
                    recognize this possibility?

          Comment:  Spec assumes that server enforces a version control
                    model. Shouldn't the client be asserting the model? At
                    least some provision should be made for client setting
                    policy rather than assume server always does so.

          Comment:  Design should support derivative work in widely
                    distributed context (i.e. design should support
                    derivative work with client asserting policy).

          Comment:  The concept of "history", dpv, indeed much of the spec
                    assumes central point of control. Monolithic thinking
                    defeats the long-term vision of "Interworking". Don't
                    be seduced into taking the easy way of server-centric,
                    single point of control - the way of the Dark Side.

          Comment:  Think in terms of "authoritative" vs "non-
                    authoritative" sources with respect to where things
                    reside (e.g., "Clear Case").

          Comment:  Interoperability is the IETF gold standard by which to
                    measure the elements of any protocol. In this case,
                    provision should be made for the client to set version
                    policy, and it should be recognized that the "tree" may
                    well be a highly distributed object with many locally
                    idiosyncratic representations. The tree might not
                    reside in a single, absolute reference frame; but the
                    client should be able to assert any logically
                    consistent framework from which to view the tree (in
                    whole or part)that can be expressed as a "well formed"

          Comment:  WEBDAV should not exclude server/server transactions.
                    Fine if WEBDAV doesn't define such transactions.

          Comment:  Design team should focus on the needs of the Internet
                    when writing spec; may help shift emphasis to
                    client/interoperability. Why not split the spec? A
                    monolithic spec leads to monolithic design!

          Presentation (continued):
               The CHECKOUT method is presented. Discovery of method
               capability is deferred to a later presentation.

          Question: Checkout function is too complicated. Must one do
                    discovery? Seems to require three-step procedure.
          Answer:   One need only ask once for server support of method

          Question: "Derived-From", wasn't this supposed to be addressable?
                    What happend here?

          Question: Where is "UNCHECKOUT"?


          Chair:    Leads a discussion on whether to seek official status
                    as a working group with the IETF, the W3C, or both.
                    Much discussion.
          Chair:    Moves for a vote on the following: Shall WEBDAV proceed
                    to seek IETF working group status with all due speed?
          Response: Motion seconded. The Ayes have it.

          Chair:    Moves that the group take ten minutes discussing the
                    following proposal: Should we split the draft spec?
          Response: Motion seconded. Passed.
                    Much discussion of pros and cons. An emerging consensus
                    to re-evaluate the situation when IETF working group
                    status is attained.

          Chair:    When should we schedule WEBDAV work group meeting at
          Response: General response indicates Monday morning would be

          Chair:    Directs editor to submit current draft to IETF asap.
          Chair:    Directs editor to post meeting notes asap, with above
                    directive taking precedence.

          Namespace Manipulation  .........          Asad Faizi, Del Jensen

          Presentation (Asad):
               Asad briefly presents COPY MOVE etc.

          Comment:  The statement "byte move or anything else" should be
                    "byte move and anything else".

          Comment:  Discoverability is fine, but how can a client enforce
          Comment:  Having different things happen at different servers is
                    a recipe for disaster.

          Hubub:    On the meaning of the phrase "byte for byte copy", much
                    discussion. What is COPY in Web context? The phrase
                    "byte for byte" not sufficiently abstract. Should be
                    phrased without reference to encoding or representation
                    of the resource data. People who cannot grasp this
                    abstraction have no business writing the specification.

          Comment:  Change the name of COPYHEAD.
          Comment:  WEBDAV header names should not mimic other header
                    names. Too confusing, even if context resolves outright
          Comment:  Should discuss on the list whether COPY/MOVEHEAD should
                    be in spec.

          [Ed. Note: The Chair also took notes on Namespace:]
                    The methods copyhead and movehead also elicited some
                    discussion. The rationale for these methods was stated
                    as being a way for clients to discover, before the
                    method is performed, the consequences of a copy or a
                    move. Participants pushed back on this, stating that
                    all that was needed was a way for clients to determine
                    what happened after a method was performed. The need to
                    discover ahead of time which links would be
                    copied/moved was also raised, and there was some

                    discussion on why predefined links might change from
                    one part of the namespace to another.
          [Ed. Note: End of Chair's Notes on Namespace]

          UNDELETE, DESTROY ..................                   Del Jensen

               Brief overview of semantics.

          Comment:  HTTP/1.1 DELETE semantics imply all access to an object
                    via HTTP is removed. Therefore UNDELETE-ing a DELETEd
                    URI does violence to the HTTP object model.

          Hubub:    Much discussion on UNDELETE and destroy, at the end of
                    which there appears to be an emerging consensus that
                    UNDELETE and DESTROY are not appropriate WEBDAV


          Lauren:   Informs the group that the XML draft spec is available
                    at <http://www.w3.org.pub/www/tr/wd-xml-961114.html>.

          [Ed. Note: The Chair kindly took notes on the following
          Method Capability Discovery ............             Yaron Goland

               Yaron gave an overview on his proposal (which he stated had
               not been previously agreed to by the design team) for method
               capability (interface) discovery, which he termed "schema

          Comments: Participants noted that the functionality described for
                    capability discovery in DAV was similar to the proposed
                    functionality for the Protocol Extension Protocol (PEP)
                    for HTTP, and there was a proposal to remove the
                    capability discovery mechanism from the WebDAV
                    specification and work it into a general-purpose HTTP
                    extensibility mechanism.

                    One participant also noted that there was a similar set
                    of functionality being proposed by the Internet
                    Printing group. Another observation made about the
                    capability discovery mechanism was that it shared some
                    similarities to an RPC-type system, and was half of an
                    interface definition language.  Participants questioned
                    whether this level of generality was needed. This then
                    led into a high-level discussion on the need for a
                    capability discovery mechanism.

                    What came out during the discussion was that the design
                    team had assumed a model where clients would have to
                    discover the capabilities of a server, then adapt
                    themselves to the current capabilities of the server.

                    Several participants stressed that a better model to
                    adopt would be to have simple clients able to operate
                    with a variety of back ends (with a minimum of
                    adaptation).  Several participants also noted that by
                    having so many different functionality options, it was
                    difficult to determine the core DAV functions that all
                    clients can depend on.

                    At the end of this session, there was a poll of opinion
                    across the participants, where each participant was
                    able to express their opinion on capability discovery. 
                    The sentiment exposed by this was that the capability
                    discovery mechanism in the current specification is too
                    complex, and too powerful for WebDAV needs.
                    Furthermore, the sentiment was expressed that it would
                    be good if the WebDAV specification could bemodified so
                    that capability discovery isn't necessary at all.

                                   End Of Meeting
Received on Friday, 7 February 1997 16:39:48 UTC

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