Open hypermedia for WWW 1Kaj Grønbæk, Aarhus University Open hypermedia for WWW Plan –Motivation –Emerging open hypermedia systems for the WWW –Utilising the Devise Hypermedia framework on the WWW –Concluding remarks 32. Serving Information to the Web with Hyper-G Andrews et al, Computer Networks and ISDN Systems 33. Designing Dexter-based hypermedia services for the World Wide Web K. Grønbæk et al, 34. The Distributed Link Service: A Tool for Publishers, Authors and Readers Carr et al

Open hypermedia for WWW 2Kaj Grønbæk, Aarhus University Why open hypermedia for the WWW? Aiming to support the visions of cooperative hypermedia that support users in seamless sharing and creation of hypermedia structures on the Internet The WWW doesn’t yet allow users’ to create links from and into materials they don’t own! WWW documents need to be changed in order to create links from them! WWW provides no support for organizing documents in individual or shared collections! The WWW does not support cooperation on documents!

Open hypermedia for WWW 3Kaj Grønbæk, Aarhus University Open hypermedia hypermedia objects in separate database - instead of embedded addresses open: no requirement for special content- formats – use applications’ own formats anchors may reference segments in any data-type, e.g. video, bitmaps integrates the users’ favorite applications via inter-application communication distinction between edit og browse user interface not necessary link relations can be inspected and maps may be generated collaborative manipulation of hypermedia structures – requires no write permission to content Go to Link object Jump-addresses: E.g. WWW Open hypermedia: E.g. DEVISE Hypermedia

Open hypermedia for WWW 4Kaj Grønbæk, Aarhus University Hyper-G Developed at Graz University of Technology, Austria, > Combines hierarchical navigation, linking, and attribute/content search Uses its own SGML document format HTF - but WWW compatible Uses its own browsers: Harmony (UNIX) and Amadeus (PC-Windows) Datamodel: document, cluster, collection, search, link Uses object-oriented database to store hypermedia objects Check:

Open hypermedia for WWW 5Kaj Grønbæk, Aarhus University Hyper-G: Datamodel example

Open hypermedia for WWW 6Kaj Grønbæk, Aarhus University Hyper-G: Architecture

Harmony User Interface

Hyper-G interface in Netscape Hyper-G pages can be viewed in Netscape with “in-page” access to attrbutes and Hyper-G menu Example: accessing external document attributes

Open hypermedia for WWW 9Kaj Grønbæk, Aarhus University Microcosm Distributed Link Service (DLS) Developed at University of Southampton, UK, > Built on top of the general open hypermedia system called Microcosm Inherits link model: Generic links, local links, specific links Attaches a pop-up menu to the titlebar of Netscape windows on PCs or spawns a separate menu application on UNIX/Motif Support compilation of DLS links into WWW documents on the fly Stores links in separate linkbases (called filters) Check: wwwcosm.ecs.soton.ac.uk/dls/dls.html Microcosm The Microcosm Home Page Fri Mar 31 13:32:34 GMT 1995 Hypermedia Research at the University of Southampton

Open hypermedia for WWW 10Kaj Grønbæk, Aarhus University Microcosm: Link concepts Specific link from an object at a specific location in a source document to an object at a specific location in a destination document Local Link from an object at an arbitrary location in a source document to an object at a specific location in a destination document Generic Link from an object at an arbitrary location in an arbitrary source document to an object at a specific location in a destination document (“object” is typically a textstring) Text retrieval links - computed destination search for string match across registered documents lookup in inverted indexes and computation of “similarity coefficient”

Open hypermedia for WWW 11Kaj Grønbæk, Aarhus University Microcosm: Architecture

Open hypermedia for WWW 12Kaj Grønbæk, Aarhus University Microcosm DLS

Open hypermedia for WWW 13Kaj Grønbæk, Aarhus University Microcosm/DLS interface

Open hypermedia for WWW 14Kaj Grønbæk, Aarhus University Microcosm/DLS interface

Open hypermedia for WWW 15Kaj Grønbæk, Aarhus University Devise Hypermedia - a step towards cooperation support Current attempts (Hyperwave, WebCosm) share a number of limitations: They are not platform independent They require special browsers (and formats) Restricted data models No explict cooperation support Devise Hypermedia for the WWW: Cooperation support is part of the general framework Aim to use a generic interface which will work with any browser (Java-based ) Provides an extensive, general and tailorable data model Advanced navigation facilities Browser and platform independence is not as easy as it should be...

Architecture for DHM/WWW Direct TCP/IP Connection

Application layer: DHM/WWW applet Opening a page via DHM/WWW

Making a selection for a link endpoint

A temporary link dialog (forced by Java security)

A source link endpoint has been created

Making a selection in a destination page

A destination endpoint has been added

Destination endpoint is marked

Overview of DHM anchors in a page

Inspection of an anchor

Open hypermedia for WWW 26Kaj Grønbæk, Aarhus University Communication Layer: CGI-script A single CGI-script to handle the protocol Link creation: webBrowser,0002, u.dk/~bouvin/DHM/""DEVISE""This is a home page for the DEVISE Hypermedia""369""6""0") Addition of endpoint: webBrowser,0102, mi.aau.dk/~kgronbak/DEVISE/""DEVISE""The name DEVISE is inspired""258""6""0") The WWWInstCom class is specialized to generate textual response to the Applet instead of launching and communicating with an application Get locSpecs: webBrowser,0900, Response - list of LocSpecs: (1,1,(" is a home page for the DEVISE Hypermedia""369""6""0"))

Open hypermedia for WWW 27Kaj Grønbæk, Aarhus University Application Layer: Structure of DHM Applet

Open hypermedia for WWW 28Kaj Grønbæk, Aarhus University Extensions to the Devise Hypermedia Framework Component WWWComponent STORAGE Instantiation WWWInstantiation RUNTIME InstCom WWWInstCom COMMUNICATIONAPPLICATION DHM/WWW Applet

Open hypermedia for WWW 29Kaj Grønbæk, Aarhus University Storage/Runtime layers Straightforward specializations and a few modifications of kernel functionality Component stores document URL as contents and modification date in an attribute Date is used to raise exceptions when documents have changed since DHM server was notified Anchor uses text selection, position and length to locate parts of documents Extensions to locate parts of other MIME-types via plug-in such as Shockwave and Quicktime is a future design issue Instantiations needs to buffer information e.g. on multiple destinations and return them in a single communication. (A little complicated in the current model) At the RUNTIME layer the handling of current link needs to be changed, since many users may interact with the same RUNTIME process

Open hypermedia for WWW 30Kaj Grønbæk, Aarhus University Towards cooperation support for the WWW Browsing: DHM/WWW provides multiple structures to the same body of WWW documents Similar to the 1985 ideas in Intermedia - providing multiple Webs Links into and from Private, public and group structures Authoring: Groups may manage and coordinate authoring of a body of WWW documents via a DHM/WWW service Assumes login to common server(s) Assumes a Java compatible DHM-extended HTML editor Lock management for distributed documents Assumes that the DHM-extended editor always requests lock from the relevant DHM/WWW server Awareness Notifications for changing WWW documents Assumes direct server to Applet communication

Open hypermedia for WWW 31Kaj Grønbæk, Aarhus University Performance issues Adding DHM/WWW links to an existing Web page requires: Establishing communication with an additional server (when we get beyond the current Java limitation) Transfer of a set of LocSpecs - typically less than 100 bytes each Processing of the HTML code to insert additional links + JavaScript control code (JavaScript not necessary in an ActiveX/Explorer solution) The overhead in terms of data transferred is quite modest compared to most Web pages containing graphics, applets, Shockwave and the like Processing of the HTML is fairly fast compared to rendering of pictures etc. The additional server requests may cause delays

Open hypermedia for WWW 32Kaj Grønbæk, Aarhus University Status DHM/WWW Java applet prototype implemented Cannot access selections in browsers due to security limitations (Netscape 4 promise a solution for this) Cannot connect to any otherserver than the one it came from(Signed Java applets promise a solution for this) CGI scripts in BETA establish communication to DHM Server process Only Applet to Server communication supported up till now A version without Locking and Awareness features demonstrated at Hypertext ‘97, April Next steps Support for cooperation Support for non-HTML pages (e.g. QT, VRML)

Open hypermedia for WWW 33Kaj Grønbæk, Aarhus University Next generation: COCONUT architecture Peer-to-peer communication using TCP/IP Three different ways of managing structures Applet Helper App. Proxy

Open hypermedia for WWW 34Kaj Grønbæk, Aarhus University Next generation(1): Navette Java Applet running in a separate window Written with a generic framework called Arakne Specially tailored for MS Internet Explorer using COM

Open hypermedia for WWW 35Kaj Grønbæk, Aarhus University Arakne framework Extensible with beans in internal frame Encapsulates browser in a single class

Open hypermedia for WWW 36Kaj Grønbæk, Aarhus University Next generation (2): Webvise Helper application Tailored to Internet Explorer using COM Catches all browser events

Webvise architecture