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WEBDAV Working Group                           Ora Lassila
INTERNET-DRAFT                                 Nokia Research Center
<draft-ietf-webdav-scenarios-00.txt>           May 1997

Expires November, 1997


         HTTP-based Distributed Content Editing Scenarios


Status of this Document

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Abstract

This document contains examples of distributed editing conducted
through HTTP. These scenarios have been developed by the Distributed
Authoring and Versioning Group in the course of specifying
requirements for distributed editing, and aim to demonstrate the
concepts of distributed editing.  The document presents a logical
hierarchy of scenarios, separating actual editing actions from
document management.

1. Introduction

The purpose of this document is to catalog scenarios of distributed
editing and authoring as well as versioning, as related to the work of
the Distributed Authoring and Versioning group, and particularly to
the Interned Draft document "Requirements on HTTP for Distributed
Content Editing" [1].  These scenarios can serve as examples of
distributed authoring and versioning HTTP extensions' usage, and can
be used as basis for discussion of various requirements and protocol
features.

The scenarios in this document have been divided into sections
addressing different aspects of the distributed authoring area: the
first section focuses on the manipulation of the contents of resources
(documents), the second section focuses on the management of the
documents themselves and their relationships to other documents and
the URL space.  A third section has also been included for scenarios
not clearly belonging to either of the first two sections.

The individuals "Jane" and "Joe", used in the scenarios, can in most
scenarios (if not all of them) be understood as either real people or
as some types of software agents.

2. Distributed Editing

This section contains scenarios where contents of resources are
changed through the use of HTTP (as opposed to through local file
system operations).

2.1. Opening and Closing Documents

Scenarios in this section illustrate opening and closing of documents
and retrieving their contents for editing.  They are related to (and
partially overlap) scenarios in section 2.2.

2.1.1. Opening Documents

Scenario A: Jane requests that document D be opened.  D is available
in English, Finnish and Swedish, each using different word processors
and each with different revision histories.

Scenario B: Jane requests that document D be opened.  D contains links
to headers, footers and graphical material.  Variation 1: Jane's
client side environment is a browser.  Variation 2: Jane's client side
environment is an editor.

Notes:

  1. In both scenarios it is important that source entities have
     meta-data identifying both the native (or "source") format (MS
     Word, Corel WP, etc.) and format revision.

  2. Scenario B also illustrates the possible desirability of
     server-side support for conversion of document source to a normal
     (canonical) form (such as HTML/MIME) for viewer/browser support.
     A typical DMS might, upon receipt of the OPEN request, retrieve
     the document meta-data and content from the store and create a
     temporary file containing the document content in its native
     format (such as Microsoft Word) on the system(s) hosting the
     store.  The DMS would then respond (via the server) with status,
     the URL of the temporary file and the document meta-data
     (establishing context for the document object).  The client-side
     process might then issue a GET request for either the source
     document (for editing), or the normal form document (for
     viewing).  Though one might expect that editing source implies
     GETting source, one must not rule out the possibility of editing
     the (temporary) source file in-situ (server side); editing server
     side in-situ is one plausible approach to collaborative editing.
     While the Extension may not initially support collaborative
     editing of a single document, the Extension architecture should
     neither proscribe such functionality nor should it favor the
     adoption of any one particular implementation architecture.

2.1.2. Checking Documents In and Out

Scenario A: Jane "checks out" a document D with an "intent to edit"
(i.e., a high probability that Jane will delete, add-to or change
document content or document meta-data).  Variation 1: Jane wants
exclusive editing rights ("write lock") to D.  Jane has no objection
to letting others view as it is edited.  Variation 2: Jane wants
exclusive editing rights to D and objects to others viewing D as it is
edited ("read/write lock").  Variation 3: Jane wants to edit a local
copy of D with the intent to merge and resolve conflicts later at
"check in".  Note that this case accommodates editing "off-line"
(disconnected mode).  Variation 4: Jane is willing to engage in
"free-for-all" editing, but wishes to make it known to other potential
editors that she is entering/leaving the melee.

2.2. Editing Documents

Scenarios in this section are related to retrieving the contents of a
document in various formats for editing.  The are related to (and
partially overlap) scenarios in the previous section.

2.2.1. Editing HTML

Scenario A: Jane, the maintainer of a web page, needs to update its
HTML source.  There are no other variants to this page, such as
translations into other languages.  She is working with a distributed
authoring tool, DistEdit.  She loads the HTML source into DistEdit via
HTTP.  She then performs some edits to the HTML source.  The HTML
source is then written back to its original URL using HTTP.  The
distributed editing session is ended.

Relevant requirements (see [1]) and/or protocol features: Source
Retrieval, HTTP PUT, Partial Write.

2.2.2. Editing a Particular Language Version of an HTML Resource

Scenario A: Jane, who is fluent in Finnish, needs to update the HTML
source of the Finnish language variant of a web page which has
English, Finnish, and Swedish language variants.  She is working with
a distributed authoring tool, DistEdit.  She loads the Finnish
language HTML source into DistEdit using HTTP, and makes some
corrections and modifications.  She then writes the HTML source back
to the original URL using HTTP.  The distributed editing session is
ended.

Relevant requirements and/or protocol features: Source Retrieval, HTTP
PUT, Partial Write.

2.2.3. Editing HTML with Server Side Includes

Scenario A: Jane needs to update the HTML source of a web page.  The
HTML source includes a server side include (SSI) directive which
instructs the HTTP server to insert the current date into the
document, and is written in English.  There are no other variants to
this page, such as translations into other languages.  Jane is working
with a distributed authoring tool, DistEdit.  She loads the HTML
source (including the source of the server side include directive)
into DistEdit via HTTP.  She then performs some edits to the HTML
source.  The HTML source is then written back to its original URL
using HTTP.  The distributed editing session is ended.

Relevant requirements and/or protocol features: Source Retrieval, HTTP
PUT, Partial Write.

2.2.4. Editing Word Processor Source which Gets Converted to HTML

Scenario A: Jane needs to update the source of a web page, stored in
the native format of the HTTP-aware word processor DistProc.  The HTTP
server containing this resource has extensions provided by the vendor
of DistProc which automatically convert the DistProc native files into
HTML which is served whenever the web page is accessed from its URL,
U.  The web page does not include any graphic content, and is written
in English.  She loads the web page source into DistProc from URL U
using HTTP, and begins to edit this DistProc native format source
file.  After making some modifications, she saves the source file back
to the original URL, U, using HTTP.  She then checks the HTML source
by retrieving URL U using their favorite web browser.  Since it looks
fine, she ends the distributed editing session.

Relevant requirements and/or protocol features: Source Retrieval, HTTP
PUT.

2.2.5. Multiple Simultaneous Editors

Scenario A: A certain Web site is maintained by two people, both of
whom make changes on an ad hoc basis.  As is frequently the case,
there are a few documents that are hot points of congestion, even
between these two people.  Both people (we'll call them "Jane" and
"Joe") have a fancy, version-aware Web authoring tool that interacts
with their Web server.

Joe downloads a document from the Web site, and decides that it needs
work.  He clicks on the "edit" button from his browser/authoring tool,
and the tool reports two things: first, that the Web server has
acknowledged his edit operation (giving him assurance that a
subsequent PUT will not be a complete surprise to the server); second,
that the document he will edit is identical to that which he viewed.
This may not always be the case: sometimes the document viewed by
users is not the true, editable source of the document.  But in this
case it is.  Joe proceeds to revamp the document.

Jane meanwhile is viewing the same document and realizes that in the
document the word "fuchsia" has a typo.  Jane also clicks the "edit"
button, but the authoring tool has a lengthier report for her: in
addition to what Joe was told, Jane is told that Joe is also working
on the same document.  Jane calls Joe and they reach an agreement:
Jane will make her fix now (because the error is embarrassing) and Joe
will make sure this alteration makes it into his revision.

Jane makes her changes and clicks the "save" button.  Her authoring
tool prompts her for a brief description of her changes, and then the
server informs Jane that her change has resulted in a new, named
revision of the document, and that name is displayed.

Joe forgets what he was doing, and weeks later (while working on
something else) clicks the "what am I working on" button.  In the long
list of documents that Joe has started to change is the document we've
been discussing, and Joe decides it is time to finish it off.  He
makes his final edits, and clicks the "save" button.  Joe, however,
gets a message indicating that what he edited is no longer the latest
version of the document, and Joe clicks the "merge" button.  The
authoring tool has the latest and greatest merge mechanisms, and in
the process of resolving Jane's work with his he realizes that Jane
did more than just fix the misspelling she said she would.  That
doesn't matter, because the merge mechanism uses actual differences,
not verbally stated intentions.

Joe again clicks the "save" button, and this time he is prompted for a
description and his new version of the document is saved.

[Continued in 3.6.1.]

3. Distributed Document Management

Scenarios in this section describe remote management of the properties
of resources, remote management of URL hierarchies (these could be
called "directories"), as well as visualization of the relationships
among graphs.

3.1. Opening/Closing Document Containers

Scenarios in this section are illustrate management of document
containers (e.g., "folders").

3.1.1. Opening a Document Container

Scenario A: Jane requests that repository R (a web, a DMS store, etc.)
be opened.  The server response to Jane establishes context for R; for
example, a list of R attributes and corresponding attribute values,
followed by a list cataloging the objects immediately subordinate to R
(folders, files, pages, whatever).  Variation 1: Jane requests by
location (URL).  Variation 2: Jane requests by identity (URI).

Scenario B: Jane requests that file F (containing document D) be
opened.  The server response to Jane establishes context for F; for
example a "reference handle" for accessing the attributes and content
of F.

Scenario C: Jane opens folder S.  In response, Jane receives context
for S.  Just after Jane's OPEN request Joe initiates a MOVE of S.

Notes:

  1. A semantic problem: how does Jane understand the object-context
     response of the OPEN well enough to make use of it?

  2. The need to support URI's as well as URL's.  We should keep a
     close eye on the URI/URC work groups (see URI specification [2],
     and see also [3]).

  3. The issue of locking resources.  In scenario C, suppose Jane opens
     S in something like a "share deny none" mode.  What might happen?
     a) The server might reject Joe's MOVE request.  b) The server
     might honor Joe's MOVE request and "shadow" the old URL for S
     until there is no pending operation or unresolved state with
     respect to S via the shadow URL.  c) The server might honor
     Joe's MOVE request and do nothing about pending operations or
     unresolved states with respect to S via the orphaned URL.

3.1.2. Closing a Document Container

Scenario A: Jane, having examined the list of container attributes for
folder S, uses an editing tool in order to change the value V1 of the
attribute A to V2.  The new attribute value has local instantiation at
the remote host(s) which are providing an environment for Jane's
editing tool.  The (server side) object S itself does not yet reflect
V2 at A.  Through some action, either explicitly (such as requesting a
"close" transaction with S) or implicitly (such as ending the edit
session) Jane asks for closure with S.  Variation 1: A second party
Joe has meanwhile requested to PUT a value to A.  Variation 2: At the
time of Jane's CLOSE request, Jane is disconnected from the network.

Scenario B: Jane has opened folder S and requested that all objects in
S not accessed within the last six months be deleted.  Before the
deletion is complete, Jane requests closure with the repository R
containing S.

Notes:

  1. The problem of encountering a race condition is the explicit
     issue raised by Scenario A.  But there is also the implicit issue
     of providing a common semantic space for Jane's editing
     environment and the server-side DMS.  In this case it would be
     nice if Jane's environment had lexicological connection with A,
     i.e., could ascertain how the value of A is represented (data
     type, range, etc.).  Semantic problems such as these are often
     resolved by promoting standard formats for the transport
     container.  Will the work group get involved with format issues?

  2. Scenario B illustrates an obvious closure issue, to wit: all
     ongoing processes and unresolved state conditions that are
     artifacts of the interaction between Jane, S and R must be
     "cleanly" terminated and resolved before closure.  Usually.

3.2. Creating Documents

Scenarios in this section illustrate various ways of creating new
documents.

3.2.1. Creating a New Resource

Scenario A: Jane is working with distributed authoring tool DistEdit
on a new HTML page which does not contain any embedded graphical
content.  She has finished her edits, and saves the HTML resource to a
web server using the HTTP protocol.  She is prompted for a URL for the
new document; the page is then written to this URL using the HTTP
"PUT" method.

Relevant requirements and/or protocol features: HTTP PUT.

3.2.2. Creating a New Resource Through a "Save As" Dialog Box"

Scenario A: Jane is working with distributed authoring tool DistEdit
on a new HTML page which does not contain any embedded graphical
content.  She has finished her edits, and wishes to save the HTML
resource to a web server using the HTTP protocol, but does not know
the exact name of the level of the URL hierarchy where she wants the
document to be stored.  She invokes the "Save As..." feature of
DistEdit, which includes a hierarchy level viewer, a list of all the
entities and their MIME types at a specific level of the hierarchy,
along with the ability to go up or down a level of the hierarchy by
clicking on either ".." to go up, or the name of a hierarchy level to
go down.  She moves up and down within the URL hierarchy using the
facilities of the hierarchy level viewer, finally finding a good
hierarchy level for the resource.  She then enters a name for the HTML
resource, and hits the "Save" button.  The DistEdit tool now writes
the HTML page to the URL created by combining the hierarchy level
selected using the hierarchy level viewer, and the name just entered
by her.  The web page is written to the URL using the HTTP "PUT"
method.

Notes:

  1. The AOLpress distributed authoring tool currently provides this
     capability, which they term "Network saving of HTML pages" using
     the "AOLpress file dialog."

  2. For file-based servers, there is typically a mapping between URL
     hierarchy levels and directories in the filesystem.

Relevant requirements and/or protocol features: List URL Hierarchy
Level, HTTP PUT.

3.2.3. Creating a New Resource in a New Hierarchy Level

Scenario A: Jane is working with distributed authoring tool DistEdit
on a new HTML page which contains some associated embedded graphical
content.  She finishes her edits, and wishes to save the HTML resource
to a web server using the HTTP protocol, as well as save the graphical
images (collectively we will call this publishing).  She invokes the
publishing feature of DistEdit, which includes the hierarchy level
viewer (as described in the previous scenario).  She finds a level of
the hierarchy using the hierarchy viewer, but since this is a new web,
she decides to create a new level of the hierarchy just to contain
this web.  Pressing the "Create New Hierarchy" button causes the
author to be queried for the name of the new hierarchy level.  Once
entered, DistEdit informs the HTTP server that a new hierarchy level
should be added below the level currently displayed in the hierarchy
level viewer.  If the author has the correct access permissions to
create a new hierarchy, the new hierarchy level is created.  The web
author then presses the "Publish" button, and his web of HTML and
graphic entities are written to the HTTP server.

Notes:

  1. The AOLpress distributed authoring tool currently provides the
     capability to make new hierarchy levels, supported by their
     "MKDIR" HTTP method.

Relevant requirements and/or protocol features: List URL Hierarchy
Level, Make URL Hierarchy Level, HTTP PUT.

3.2.4. Visualizing Webs as Graphs

Scenario A: In order to understand the link structure and resource
inclusion relationships at a hierarchy level, a web maintainer chooses
the "Graph View" option of their distributed editing tool DistEdit.
DistEdit queries the web maintainer for which level of the hierarchy
to display using a graph visualization, and then uses the HTTP
protocol to read information about that level of the hierarchy.
DistEdit uses this information to display a graphical visualization of
the hierarchy level, including an icon for each resource, solid lines
between the icons representing links, and dashed lines representing
inclusion (for example, images loaded using the IMG tag).  Entities
the web maintainer has read and write access to are displayed in
green, those which they have read access to are in white, and those
which they have no access to are in red.  To create the graph
visualization, DistEdit must, using HTTP, get a listing of all the
entities at a level of the hierarchy, and their access control
permissions.

Notes:

  1. The AOLpress distributed authoring tool currently provides a
     similar capability, which they term the "MiniWeb," a "bird's-eye"
     graphical view of web site documents and how they are linked
     together.

  2. The FrontPage distributed authoring tool provides equivalent
     capability, which they call a "Link View," and also supports the
     related "Outline View" and "Summary View."

Relevant requirements and/or protocol features: List URL Hierarchy
Level.

3.3. Attribute Management

Scenarios in this section illustrate management of document attribute
data, and the administration of access rights.

3.3.1. Getting Attribute Values

Scenario A: Jane submits a list of document URIs with the request that
the "subject/summary" attribute value be returned for each document.

3.3.2. Modifying/Setting Document Attribute Values

Scenario A: Jane requests that the value of the document attribute
"subject/summary" for document D be modified to correct an error.

Scenario B: Jane is creating a new document on the Web.  She sends it
to the server, but also wants to set a bunch of attributes that can be
used later in searches (author, title, type of document, subject,
organization, etc.).  Sometimes she may also want to create catalog
entries for documents that are not available in electronic form.
There will be no content for these documents, just attributes.

Relevant requirements and/or protocol features: Attributes.

3.3.3. Access Control

Scenarios in this subsection illustrate various situations of
assigning, modifying and revoking access rights to a document or group
of documents.

3.3.3.1. Modifying Access Rights

Scenario A (Realistic): A sales manager at a company which contains an
organization-wide intranet is working with an intranet-enabled
spreadsheet program, DistCalc.  After entering the sales figures for
the previous month (which are below projections), a graph of the sales
figures is generated as a JPEG image, and then saved to the
departmental HTTP server using the HTTP "PUT" method.  Realizing that
it might be best to limit access to this information, in their web
browser they bring up the graph image.  After selecting the menu
option, "Modify Access Permissions," the browser displays the access
control page for the graph image resource.  The sales manager uses the
(server-specific) facilities on this page to modify the sales chart's
access control rights so it is password protected.

Scenario B (Ideal): In the ideal case, the DistCalc program would
display a dialog box asking the user for what access rights the graph
resource should have before the graph is saved to the departmental
HTTP server.

Notes:

  1. The "realistic" case assumes that reaching consensus on an access
     control standard for HTTP resources is not achievable in the near
     term, and hence access control will vary with server type.  It
     also assumes a continuation of the current trend of having an
     access control URL for each resource.  The "ideal" case shows
     what could be achieved if an HTTP access control standard is
     created.

No matching requirements or protocol features.

3.3.3.2. Using Special Access Rights

Scenario A: A museum's paintings are being made available online.
There are several different collections of paintings with different
access rules.  Paintings may migrate from one collection to another
from time to time.

  1. One collection, meant to entice visitors into the museum, is
     freely available to all.

  2. In another collection, anyone can view metadata or retrieve a
     low-resolution rendition of any painting for free, but retrieval
     of a high-resolution rendition requires payment of a fee.  Museum
     members can retrieve even high-resolution renditions from this
     collection without charge.

  3. A children's collection lets children submit art works.  The
     child registers when he submits an art work.  Any child can add,
     remove, or modify his own work.  Anyone can view works in this
     collection for free.  Access control for this site can be managed
     by creating the three collections, and setting access rights for
     each collection at the server.  The curator can move paintings
     from one collection to another with a Web-based tool.  The museum
     application enforces access rights by consulting the museum's
     membership database and the children's registry, together with
     the access policies.

Scenario B: A university library wants to put reserve readings on line
for its students.  In order not to violate any copyright laws, it
needs to set permissions so that only students registered for a
particular course can view the readings for that course.  The
librarian putting the reserve readings online is using a Web-based
tool.  Whenever he adds a reading to the Web site, the tool prompts
him for the course numbers whose students should be allowed to access
that reading.  The reserve readings application at the Web server is
tied to the course registration database to enforce these permissions
when students try to access materials.

Scenario C: Some products support a notion of community-administered
Web sites. Anyone can set up an account for himself at one of these
sites.  Then, when logged on as himself, he can add collections and
materials to the site, and determine access rights for any objects he
adds.  He can change these access rights at any time.  He can create
groups and users, and administer the groups and users he owns or has
permission to administer.

Notes:

  1. Xerox's DocuShare system supports Scenario C.

3.3.3.3. Access Rights and Document State

A team is working on a project that involves sensitive business data.
The project's deliverables include several papers, each of which goes
through several cycles of writing and review before it is approved for
distribution.  A person who is an author of one paper may be on the
review team for several others.  Outside reviewers are also engaged
for each of the papers. While a paper is in a writing phase, only its
authors have write access to it, and only project team members have
read access to it.  When a paper is in a review cycle, read and print
access is extended to reviewers.  This access is removed once review
is complete.  When a version is approved for distribution, a short
list of users throughout the company is given read and print
permission (each of these users can print at most one copy); a longer
list can read the paper, but not make printed copies.  The project
lead assigns people to the authoring and reviewing groups and
distribution lists for each paper, and determines when each paper
moves from one phase to another.  All this is done with Web-based
tools.

3.3.3.4. Access Rights and Versioning

A versioned document describing a company's product offerings is being
developed at a Web site.  It is expected to evolve over time as
product offerings change.  The team leader designates one version of a
document as the public version.  Everyone in the world has read access
to this version.  The team leader can change which version is the
public version at any time.  The team leader also gets to decide which
version of the document team members are allowed to modify at any
time.  Only team members have write access to this version.  Any other
versions are viewable, but not modifiable, by team members.  The team
leader makes these changes to the access restrictions on versions
using a Web-based tool.

3.4. Copying, Moving and Deleting

Scenarios in this section illustrate typical "housekeeping" involved
with managing documents, such as renaming, moving them around, and
deleting them.

3.4.1. Copying Documents

Scenario A: Jane is looking at the list of monthly reports available
on the server.  She selects one from the list that she wants to use as
the basis for a new monthly report.  She asks for a copy of this
monthly report to be made in the same directory but with a different
name.  Since she is not intending to work on it now, there is no
reason to pull the content to the client.

Relevant requirements and/or protocol features: Copy.

3.4.2. Copying Document Containers

Scenario A: Jane directs that folder S1 be copied to folder S2.  While
the copy is in progress, Joe directs that S1 be moved to folder S3.

Scenario B: Jane directs that a container F be copied to a location
outside the repository R.  Although F contains only a simple text
document, the structure of F both as a logical and a physical entity
is highly idiosyncratic, being intimately bound to R.  Consequently, F
cannot be expressed in the external domain.  Variation 1: The DMS has
export capability (to the external file system) with a granularity
that can resolve F.  Variation 2: The document contained by F has a
native format corresponding to the tool used to generate the document
(HTML, WPD, etc.).  In this case one could interpret the copy as a
transform from F in the DMS domain to the native document format D in
the external domain.  Variation 3: The container to be copied is
folder-like, i.e. a proper container, and the container hierarchy in R
is compatible with the external domain container hierarchy.  In this
case, some kind of copy/transform could be implemented, with the
understanding that container attributes might be largely distorted or
lost.

Notes:

  1. Copying within R should be no big deal, though scenario 6a does
     illustrate why one might desire some kind of "read-lock"
     mechanism. As scenario B illustrates, copying container structure
     and content from one repository to another can be problematical.
     For example: how does one, in general, map a plex container model
     to a hierarchical model?

3.4.3. Deleting and Undeleting Documents

Scenario A: Jane directs that page P and all subordinate objects be
deleted from web W.  Pn is subordinate to Pk is subordinate to P, and
both Pk and Pn are in scope (i.e., in W).  It so happens that Pn
forward links to Pk.  The delete process DEL recursively chains down
from P, eventually encountering Pk, and asserts a "read lock" on Pk
preparatory to deleting Pk.  Since Pk has subordinate links, DEL
continues down the chain until it encounters Pn, where it asserts a
"read lock" and recursively chains forward to Pk.  DEL requests a
"read lock" on Pk.

Notes:

  1. Document deletions (like container deletions) can be subject to
     qualifying conditions such as meeting query and scope criteria.

  2. Developers must be wary of deadlocks.

3.4.4. Deleting and Undeleting Document Containers

Scenario A: Jane opens folder S and examines its content.  Jane
decides to delete all non-folder objects in S, but is unsure if
existing folders subordinate to S have valuable content.  Jane directs
that all non-folder objects in S be deleted.

Scenario B: Jane directs that folder S and all subordinate folders and
content be deleted.  A document subordinate to S is currently open to
Joe.

Scenario C: Jane directs that file F containing document D be deleted.
A copy process of D to some other repository is in progress.

Scenario D: Jane directs that all containers and related content
subordinate to folder S with content that has not been modified since
a given date (supplied by Jane or otherwise provided) be deleted.  One
or more active documents in the repository reference a common header
that is in a file F subordinate to S.  F meets the delete criterion.

Scenario E (Undeleting): Container S1 (subordinate to S) and all
subordinate containers have been deleted.  Jane requests that
container S3 and all subordinate objects be undeleted, where S3 was
subordinate to S2 which in turn was subordinate to S1.  Variation 1:
The container structure is "plex", so that S3 was also subordinate to
Sk which was not subordinate to S1.

Notes:

  1. The delete might need to act within the context of query results
     on container/content attributes as well as scope conditions on
     the store hierarchy.

  2. B and C show how "locking" might be a good thing.

  3. D illustrates how someone might wish to incorporate a "reference
     count" attribute on linked objects, and desire that reference
     count values be appropriately factored into the query/scope
     constraints for certain kinds of transactions.

3.4.5. Moving Documents

Scenario A: Jane notices that after recently editing the content of a
document its assigned name no longer makes logical sense. She decides
to rename the document.  She selects the document from a list of
existing documents and is prompted for a new name.  Since she does not
intend to work on it now, there is no reason to pull the content to
the client.

3.4.6. Moving Document Containers

Scenario A: Jane directs that folder S1 be moved to folder S2.  In the
container hierarchy, S2 is subordinate to S1.

Scenario B: Jane directs that container S1 be moved to container S2.
There exists in web W a page P that is external to S which makes
(forward) reference (via URI) to one or more objects in S.

Notes:

  1. Again we see in the second scenario why it might be desirable to
     support the URI initiative.

3.5. Working with Multiple Documents/Resources

Scenarios in this section illustrate situations where manipulation of
a (logical) collection of related document is necessary.

3.5.1. Printing a Multi-Resource Document

Scenario A (Browsing): A net surfer browsing the web loads the
introductory page for a book which has been written in HTML and
subdivided so that there is a separate resource for each chapter, and
many side links to clarifying text and standalone figures.  Since the
book is of interest, the net surfer would like to print the entire
document.  Clicking on the "Print" button of their web browser brings
up the Print dialog box, which contains an option, "Print
multi-resource document," which they select, before pressing the
"Start Printing" button.

The browser now begins, in the background, to load all of the chapters
of the book along with their explanatory sidebars, sending them one by
one, in order, to the printer.  When complete, the browser pops-up a
dialog box stating that the document has been completely printed.

Scenario B (Distributed Authoring): This scenario applies equally well
to a distributed authoring situation.  If the author of a
multi-resource document is using a distributed authoring tool to write
the document, it is desirable for them to be able to print the
document as a whole, rather than by loading and printing each resource
in turn.

Notes:

  1. This type of printing capability is supported by the KMS
     hypertext system, an early monolithic (but very feature-rich)
     hypertext environment.

  2. Another common example of a multi-resource document which would
     be desirable to print as a whole is a slide presentation which
     has been converted into HTML.

3.5.2. Quick Browsing of Related Resources

Scenario A: A professor is working on a new textbook using their
favorite intranet-enabled word processor, DistProc.  Once the initial
draft of this book is complete, they use the "Publish" feature of
DistProc to save their book as multiple resources, one per chapter, on
a web server.  Since the author intends for their students to read the
text using web browsers employing a DistProc reader plug-in, the
professor has the book on the HTTP server in DistProc native format,
preserving layout information.

In order to provide additional browsing structure to the students, the
professor uses the feature of DistProc to automatically create links
to the table of contents, index, and glossary for the book.  To make
generating feedback easier, all book chapters automatically have a
link to a corrections and feedback page.  As the students are reading
the text, these automatic links are displayed as special toolbar icons
in their browser.

Notes:

  1. The AOLpress distributed authoring tool currently "allows pages
     to add toolbar buttons on the fly using the HTML 3.2

       <link rel ...>

     -tag.  For example, your page can add toolbar buttons that link
     to a home page, table of contents, index, glossary, copyright
     page, next page, previous page, help page, higher level page, or
     a bookmark in the document."

  2. The scenario above is currently unachievable because LINK tags
     are only supported in HTML.

3.6. Publishing and Reverting

These scenarios are hopefully illustrative of the need of a versioning
scheme for distributed editing.

3.6.1. Revising a Set of Documents and Publishing Them When Complete

[Continued from 2.2.5.]

Scenario A: Jane and Joe's version-aware web server is fairly simple:
normally, it serves up the latest revision of each document, but if
instructed it will instead serve up the revisions of documents as
listed in a named configuration.  In this way, they can make their
trivial changes and have them show up immediately, but if they plan to
make a heavy-duty overhaul they can save the current set as a working
configuration and tell the server to use those until the work is
complete (this can all be carried out without the explicit knowledge
of Jane and Joe's authoring tool, because the Web server makes itself
configurable via Web pages with forms on them).

Joe is about to make a set of minor changes, and to be on the safe
side tells the server to save the current configuration as "stable", a
name he uses for these occasions.  He goes through the various
documents, clicking "edit" on any that he thinks are in need of
updating.

Once again Joe forgets what he is doing, but a few days later the
"what am I working on" button again comes in handy.  He realizes that
his work is about complete, and makes his final edits.

Joe's changes really are a coherent set that should appear
simultaneously, and he doesn't want to find out halfway through saving
that Jane has made changes that need merging, so he clicks the "Save
All" button.  Fortunately, Jane has been busy viewing other parts of
the web and hasn't made any changes to their local Web pages, and so
Joe is prompted for a description of the changes he has made.  Since
Joe is saving all the documents at once, a single description applies
to all the changes.  One by one the new documents are saved, and in
the end Joe gets confirmation that all documents are in place.  Joe
browses the result and is satisfied that their customers are seeing
what he has just finished.

Joe goes on vacation.

[Continued in 3.6.2.]

3.6.2. Reverting the Revised Document Set

[Continued from 3.6.1.]

Scenario A: Jane gets back to real work and realizes that every
document that Joe edited has the same old spelling problem.  In a
panic she calls Joe but realizes that he is on vacation.  Knowing that
the errors would harm their image, she decides to undo what Joe has
done until he returns and can correct his mistakes.

Jane begins by browsing the revision history of each document, and
notes that all the erroneous documents came about at the same time
when Joe saved his changes just before vacation.

Jane browses the configuration lists in the version-aware web server
and sees that Joe had made a "stable" configuration before his latest
work.  Jane instructs the server to serve up only documents from the
"stable" configuration.  As this doesn't involve changing any of Joe's
work, it is a quick fix to the pages on their public web server.  Jane
now browses the documents on their server and is satisfied that they
are the precursors to Joe's latest change.

When Joe returns, he fixes his spelling mistakes and then tells the
server to resume using the latest documents.

4. Versioning Issues

Versioning (the ability to retain revision histories for documents) is
discussed in several scenarios in this document.  Section 3.6
(Publishing and Reverting) presents scenarios where versioning is
necessary, as well as section 2.1.2 (Checking Documents In and Out)
variation 3 and section 2.2.5 (Multiple Simultaneous Editors). The
relationship between versioning and access privileges is discussed in
section 3.3.3.4 (Access Rights and Versioning).

5. Miscellaneous Scenarios

Scenario A: Jane's department keeps its documents organized in
hierarchical collections.  There is a collection called "Monthly
Reports" with subcollections for each month.  There is also a
collection called "Monthly Business Letters" with subcollections for
each month.  The monthly reports are used to derive the monthly
business letters, so the monthly reports appear in the appropriate
"Monthly Business Letters" subcollections as well.  When Jane writes
her monthly report, she puts it into Monthly Reports/199608 and into
Monthly Business Letters/199608.  Only one copy of the report should
exist on the server, but it appears in both places when users browse
or search the collections.

Scenario B: The first time Jane's monthly report gets printed, it gets
converted to PostScript, which she wants to store on the server.  Now
there will be two renditions of the same (versions of the same)
document from which she can choose when she retrieves the document in
the future.  She also saves the printing instructions (duplex,
landscape, stapled, etc.)  for the document, which she may want to
retrieve with the PostScript later.

6. References

[1] Jim Whitehead, 1996.  "Requirements on HTTP for Distributed
    Content Editing", Internet Draft (available on-line from the
    Internet Draft collections as draft-whitehead-http-distreq-00.txt)

[2] Tim Berners-Lee, 1994. "Universal Resource Identifiers in WWW - A
    Unifying Syntax for the Expression of Names and Addresses of
    Objects on the Network as used in the World-Wide Web", Request for
    Comments #1630

[3] --, "Uniform Resource Identifiers", available on-line as
    http://www.acl.lanl.gov/URI/uri.html

[4] J.A.Slein, F.Vitali, E.J.Whitehead and D.G.Durand, 1997.
    "Requirements for Distributed Authoring and Versioning on the
    World Wide Web", Internet Draft (available on-line from the
    Internet Draft collections as
    draft-ietf-webdav-requirements-00.txt)

Acknowledgments

The following people have contributed to this document by submitting
sample scenarios and/or by commenting:

   * Eui-Suk Chung, Ericsson, euisuk@w3.org
   * Del Jensen, Novell
   * Dave Long, dave@sb.aol.com
   * Christopher Seiwald, Perforce Software, seiwald@perforce.com
   * Judith A. Slein, Xerox, slein@wrc.xerox.com
   * Jim Whitehead, UC Irvine, ejw@ics.uci.edu

Author's Address

Ora Lassila

Nokia Research Center / Boston
3 Burlington Woods Drive, Suite #250
Burlington, MA 01803

Phone:  +1 (617) 238-4908
Fax:    +1 (617) 238-4949
E-Mail: ora.lassila@research.nokia.com


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