Versioning and Configuration Management of
World Wide Web Content

This page was previously the home page for a working group on adding versioning and configuration management capabilities to the World Wide Web. This working group has now been split -- the current working group is now focusing on remote configuration management of web content. Discussion of WWW versioning issues now takes place in the WWW Distributed Authoring and Versioning Working Group (webdav).

This page is still an excellent resource for pointers to work on WWW versioning and configuration management, as well as hypertext versioning.

Discussion List

Discussion of the addition of configuration management capabilities to the World Wide Web takes place on the discussion list <>. Requests to join this discussion list may be sent to <> . Discussion on this list is also archived.

Existing Work and Proposals

==> Four Lessons Learned from Managing World Wide Web Digital Libraries,
Robert Pettengill and Guillermo Arango

This early paper describes a development and maintenance process for a "digital document library" (a.k.a., a collection of WWW content), the need to make this process repeatable and as automated as possible, and the use of separate maintenance and publications areas for visibility control. More relevant to this audience, the paper describes the need for using version control on web content, the addition of a ",version" to the requested URL, and explains the use of CGI scripts to provide versioned access to a document collection.

==> Mortice Kern Systems (MKS) Integrity Engine
Integrity Engine Data Sheet

MKS has developed HTTP server extensions for checkin, checkout, and locking operations on specific entities. Individual versions of an entity may be accessed by specifying the version with the addition of ";version=" at the end of the requested URL. The MKS approach, described in a white paper, makes no modifications to HTTP, and instead decorates the requested URL with the information of the desired operation.

==> P3 Software web://keeper

P3 software has performed an integration of the P3 Configuration Management system with the Apache server, which P3 has named web://keeper, thus allowing GETs of versioned URLs on any object within a P3 repository.

==> WWW Versioning Support, draft proposal (v 0.1) (Postscript)
Jim Whitehead

This working draft describes a proposal for extending the HTTP protocol with four new methods, FLAG, LOCK, UNLOCK, and USE, and describes how they are used to provide style-independent versioning with semantics controlled by the client. Two appendicies give examples of how the RCS and CVS styles are implemented using these methods. The proposal also describes a new entity type, the configuration, which allows the versions of a collection of related entities to be described in a single file.

==> NTT Software Laboratories, Palo Alto

NTT Software Laboratories in Palo Alto (SPLA) recently announced on the HTTP Working Group mailing list that they have completed a prototype of an HTTP server which manages versions and configurations of web objects. While they apparently have a white paper which is written in Japanese, and is currently undergoing translation into English, some technical details were reported in the post. The versioning and configuration functions were implemented using LINK, PUT, and "related methods". Clients which understand how to use these new functions have also been developed.

The NTT server is written in Perl. Two clients were developed, one using MetaCard, a GUI builder, along with a libwww library extended to handle the additional methods. The other client was written in Java.

==> Authoring Tools Breakout Session at WWW4
Detecting Update Conflicts in HTTP

The authoring tools breakout session identified the "lost update" problem (when people performing parallel development on an entity overwrite each other's changes) as an open issue requiring attention. David Long of NaviSoft and Dan Connolly of W3C subsequently produced a W3C working draft on the lost update problem titled, Detecting Update Conflicts in HTTP. This working draft presents four levels at which this problem may be resolved: do nothing, detect lost updates, prevent lost updates, and fairly prevent lost updates.

==> Formal Modeling of a Resource-Leasing Extension to HTTP
Rafal Boni, Rohit Khare, and Matthew Levine

This paper describes a check-out/check-in scheme for HTTP which aims to guarantee exclusive write access to a resource while it is checked-out. The scheme described does not handle parallel development of resources. The paper begins with a detailed discussion of the four-levels of potential resolution of the lost update problem identified at the authoring tools breakout session.

==> Using Versioning to Support Collaboration on the WWW,
Fabio Vitali, David G. Durand

This paper, presented at the WWW4 conference, presents a different, interesting perspective on how versioning of WWW content may be performed. Their approach is motivated by how to support asynchronous collaboration in the creation and editing of text documents, which they feel requires extremely fine-grain versioning. This paper describes VTML, the Versioned Text Markup Language, which is a markup language for describing the version history of a document. The VTML approach has the drawback that it only applies to HTML content, and does not address the versioning of bitmap images, an important class of web content.

==> Original Design Issues: Versioning,
Tim Berners-Lee

The World Wide Web Consortium has an archive of notes dating from the original design of the web in 1990. One of the issues is "keeping track of previous versions of nodes and their relationships."

==> Livelink Library for Document Management
Open Text Corporation

This marketing blurb for the Livelink Library, a component of Open Text's Livelink Intranet product, describes web content versioning capabilities including a change history, viewing of previous versions, and a lock-based overwrite protection scheme. Unfortunately, it is impossible to determine the underlying technical approach from the information presented.

Distributed Web Content Authoring Tools

==> Microsoft FrontPage
FrontPage: A Technical Overview

Microsoft FrontPage, formerly Vermeer FrontPage, is an HTML editor which can save work to an HTTP server which has been augmented with the FrontPage server extensions. Section C of the FrontPage technical overview describes the FrontPage server extensions in more detail, including its use of the POST method for writing content to an HTTP server.

The Internet Development site at Microsoft offers a wealth of additional material. Documents are available which describe Microsoft API calls in the client side to go over the web to talk to server-side. It also provides access to beta and alpha releases. Content changes daily. The overview paper is pretty interesting, since it may provide a convergence for document objects at a higher level than DMA provides - that is, cross-net delivery of content at the UI object level via OLE.

==> America Online PrimeHost AOLpress and AOLserver
Documentation for AOLpress and AOLserver

The AOL PrimtHost hosting Service, formerly known as GNN Hosting Service, fromerly known as NaviSoft, provides a service for using their GNNpress software to publish web pages on their server for a monthly fee. Since you can currently The America Online PrimeHost hosting service, formerly known as the GNN Hosting Service, which in turn was formerly known as NaviSoft, provides a service for using their AOLpress software to publish web pages on their server for a monthly fee. Since you can currently download fully-functional, but non-supported versions of their AOLpress and AOLserver tools, it is also possible to experiment with these tools.

AOLpress employs the PUT method to write content to the AOLserver, which implements access control features which control, among other methods, who can PUT to particular namespaces within the server. The documentation for the AOLserver describes how it distinguishes BROWSE, PUT, MKDIR and DELETE as different administrative rights on operations.

==> Netscape Navigator Gold
Navigator Gold Data Sheet

Netscape Navigator Gold provides authoring of HTML documents, along with publishing capability. Navigator Gold uses the FTP protocol to write content into the namespace of the HTTP server.

Hypertext Versioning Literature

The topic of hypertext versioning has been researched outside of the WWW context within the academic hypertext community for several years, and offers many insights into the WWW versioning problem. Versioning of hypertexts was addressed by Ted Nelson in Literary Machines, and in Engelbart's NLS journal facility in the 60's and 70's. This issue was revisited and given renewed importance by Frank Halasz in his extremely influential paper, "Reflections on NoteCards: Seven Issues for the Next Generation of Hypermedia Systems," published in Communications of the ACM in July, 1988, in which he lists hypertext versioning as issue number 5. These issues were reexamined in a keynote address given by Halasz at Hypertext'91.

==> Proceedings of the Workshop on Versioning in Hypertext Systems, at
ACM European Conference on Hypermedia Technology (ECHT'94)
David Durand, Anja Haake, David Hicks, Fabio Vitali

The proceedings from this workshop features papers on hypertext versioning in technical documentation, legal applications, and design, giving both requirements and solutions in these areas.

==> Palimpsest: A Data Model for Revision Control (Postscript)
David Durand
In Proceedings of the CSCW'94 Workshop on Collaborative Hypermedia Systems, Chapel Hill, NC, available as GMD Studien Nr. 239. Gesellschaft f r Mathematik und Datenverarbeitung MBH 1994.

The intellectual precursor to VTML, Palimpsest is a data model for flexible merging and tracking of individual changes to shared hypertext or multimedia documents. This work is motivated by providing support for collaborative hypertext editors where multiple people may be working on the same document simultaneously.

==> Version Control in Hypertext Systems,
David L. Hicks, John J. Leggett, and John L. Schnase

This paper, published as a technical report of the Hypermedia Research Lab at Texas A&M University in 1991, is an early, influential paper which examines many different versioning systems, and then describes how the Personal Information Environment (PIE) system (described in "A Layered Approach to Software Design," by Ira P. Goldstein, and Daniel G. Bobrow, published in the book "Interactive Programming Environments," edited by David R. Barstow, Howard E. Schrobe, and Erik Sandewall.) layered data model can be used for hypertext versioning. The paper also gives requirements for hypertext versioning.

==> VerSE: Towards Hypertext Versioning Styles,
Anja Haake and David Hicks,
Proc. Hypertext'96, the Seventh ACM Conference on Hypertext, 1996, pages 224-234.

==> Under CoVer: The Implementation of a Contextual Version Server for Hypertext Applications,
Anja Haake,
Proc. 1994 European Conference on Hypermedia Technology (ECHT'94), pages 81-93.

==> Take CoVer: Exploiting Version Support in Cooperative Systems,
Anja Haake and Jörg M. Haake,
Proc. ACM INTERCHI'93, Conference on Human Factors in Computing Systems, 1993, pages 406-413.

Anja Haake has been performing excellent research on hypertext versioning for several years at GMD-IPSI. The papers listed above represent her most recent work, and provide a comprehensive description of her research.

==> Structural and Cognitive Problems in Providing Version Control for Hypertext,
Kasper Østerbye,
Proc. Fourth ACM Conference on Hypertext (ECHT'92), 1992, pages 33-42.

This paper is notable for its clear distinction between structural (data modeling) and cognitive (interface) issues of hypertext versioning, and its detailed discussion of each. It also describes the versioning facilities of the HyperPro system.

Relevant Software Configuration Management Literature

There is a large literature on software configuration management, including proceedings from the six software configuration management workshops (the most recent of which was SCM6, held in conjunction with the 18th International Conference on Software Engineering (ICSE18)). Papers on SCM also appear in the proceedings of ICSE. Papers listed below are ones that either have particular relevance to WWW versioning and configuration management, or provide relevant background material.

==> Configuration Management Models in Commercial Environments
Peter H. Feiler
Software Engineering Institute Technical Report CMU/SEI-91-TR-7

This early survey of configuration management tools contains an excellent breakdown of these systems into four configuration management models, or styles: checkout/checkin, composition, long transaction model, and the change set model.

==> A Generic Peer-to-Peer Repository for Distributed Configuration Management
André van der Hoek
Proceedings of the 18th International Conference on Software Engineering, Berlin, Germany, March, 1996.

This paper presents the NUCM system which allows for a NUCM client to contact a distributed SCM repository and interact with it using primitive operations, upon which are implemented higher-level CM styles. If an analogy is made between a client of the NUCM system and a user-agent, and between a NUCM repository and an HTTP server, this paper has tremendous relevance for WWW versioning and CM.

==> Distributed Revision Control Via the World Wide Web
Jürgen Reuter, Stefan U. Hänßgen, James J. Hunt, and Walter F. Tichy
Proceedings of the Sixth International Workshop on Software Configuration Management, Berlin, Germany, March, 1996.

This paper describes a forms-based interface to the RCE (Revision Control Engine, essentially an API to an RCS-like core of functionality) which allows checkout, checkin, and viewing the version history of artifacts in a distributed manner via the WWW. The system described in this paper does not modify the HTTP protocol, instead relying on custom MIME types (and associated helper applications) along with point-to-point socket connections to handle the file tranfers associated with checkout and checkin operations.

==> Configuration Management Yellow Pages
André van der Hoek

This is simply the best one-stop index to the burgeoning SCM tools market, general information pages on CM, conferences on CM, job openings, public-domain CM systems, consulting, education, reviews, and more! Outrageously comprehensive.

University of California, Irvine
Jim Whitehead <>
Department of Information and Computer Science
247 ICS2 #3425
Irvine, CA 92697-3425

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