The annotation of web pages, and the possibility to share the notes with others, seems to be a powerful tool. Although several tools already provide such possibility, they are not as widely popular as one would expect them to be. We try to explain this fact, and propose a novel architectural approach that is, in our view, particularly suited to some particular domain such as e-learning. We also present a tool that implements the proposed architecture

Ronchetti, Marco

English

Unitn-eprints Research

  
 
 
 
 
 
UNIVERSITY 
OF TRENTO 
 DEPARTMENT OF INFORMATION AND COMMUNICATION TECHNOLOGY 
  
38050 Povo – Trento (Italy), Via Sommarive 14 
http://www.dit.unitn.it 
 
 
 
 
 
 
 
 
 
 
 
 
 
WHY WEB PAGES ANNOTATION TOOLS  
ARE NOT KILLER APPLICATIONS?  
A NEW APPROACH TO AN OLD PROBLEM  
 
Marco Ronchetti 
  
 
 
2002 
 
Technical Report # DIT-02-0062 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
. 
WHY WEB PAGES ANNOTATION TOOLS ARE NOT 
KILLER APPLICATIONS? A NEW APPROACH TO AN 
OLD PROBLEM 
Marco Ronchetti 
Dipartimento di Informatica e Telecomunicazioni 
Università di Trento 
Via Sommarive 14, Povo Trento Italy 
Marco.Ronchetti@dit.unitn.it 
ABSTRACT 
The annotation of web pages, and the possibility to share the notes with others, seems to be a powerful tool. 
Although several tools already provide such possibility, they are not as widely popular as one would expect 
them to be. We try to explain this fact, and propose a novel architectural approach that is, in our view, 
particularly suited to some particular domain such as e-learning. We also present a tool that implements the 
proposed architecture.  
KEYWORDS 
e-learning, annotation 
1. INTRODUCTION 
 
The idea of annotating Web pages is not a new one: early proposals date back to the pioneer-age of the 
WWW. Such functionality is appealing because it stresses the collaborative character of the Web, and it is 
rather surprising that the idea did not have a large degree of success.  
In particular, a tool providing the ability to add notes to a web page, and to share the note with other 
users seems to be particularly well suited to an e-learning environment. In fact, e-learning platforms aim 
not only at providing content to the student: in order to be effective they must support the learning process. 
For this reason virtually every e-learning suite provides at least some tool for asynchronous collaboration, 
like bulletin boards etc. Very often however these tool offer a poor degree of integration with the content of 
the e-courses. In many cases discussion among the “actors” (students and teachers) is carried on a forum: 
that means that the discussion lives in a space that does not coincide with the one where the presentation 
material is located. While sometimes this is perfectly acceptable, in many cases it is rather inconvenient 
since the discussion happens out of context, and many external references are necessary, making the whole 
process rather cumbersome. 
Annotations on a Web page could in many cases be used instead of forums. A forum is certainly very 
well suited for the discussions of broad topics. In many cases however the emphasis is on clarifying a point 
in a lecture. For instance, in the context of a programming course students are likely to be discussing the 
code presented in an electronic lecture: in those circumstances, continuous references to “line X of code Y 
on page Z” make the writing and reading of the comments an exhausting task. A comment written in a note 
posted on the referred page would be much more direct, because it would be enriched by the context. 
Other uses might include the homework: students could answer question by annotating pages, or could 
return their homework by posting it as a web page, that the teacher could grade by adding notes to it. 
Given the richness of scenarios that could be supported by web annotation, it is really puzzling that the 
tools publicly available on the web do not encounter more favor. In fact, since the early web years, sever 
projects have produced various powerful tools for annotating pages. A list of them can be found on the 
“Collaboration, Knowledge Representation and Automatability” page of the W3C [COL], and a 
comparison among several such tools is available in [GAR]. 
We believe that lack of a wide success can be probably traced to a few different factors. On the one 
hand, too much a broad scope for an idea can be counterproductive: most tools try to solve the problem of 
“annotating whatever page you want, wherever it is”, and, to our knowledge, do not try to address a 
specific domain. We believe that it is often better to address specific needs of a restricted domain  in a 
precise way rather than offering a “Swiss knife” solution, i.e. general support for a rather vague 
functionality.  
Another factor might be the absence of a ripe technology, that forces to use hacks ending up with a 
rather clumsy product. Early efforts were certainly penalized by the absence of a suitable technology. The 
resulting (annotated) pages were rather heavy, for instance using frames for showing the notes, or adding 
the annotations as footnotes, making the reading of the page sub-optimal.  
Recent attempts (e.g. [KOI]) try to leverage the newest technologies, like the Resource Description 
Framework (the RDF specifications [RDF] provide a lightweight ontology system to support the exchange 
of knowledge on the Web), and use the notion of Xlink [XLI] and Xpointer [XPO]. Such a road, although 
very interesting and probably correct on the long run, makes the deployment of the tool now (and in the 
near future) almost impossible: the Amaya [AMA] browser is the only one that supports such technology.  
In the light of these considerations, we revisit the idea of web pages annotation. We restrict the focus to 
the domain of e-learning; we examine the existing software architectures supporting the annotations, and 
propose a different architectural approach. We also examine the technology that is available now in a 
standard way to obtain a user interface that is suitable for our application domain. Moreover, we set as a 
requirement the possibility of integrating our proposed approach in (virtually all) e-learning platforms. 
Finally, as a proof of concept, we implement a portable tool that allows introducing annotations in existing 
e-learning systems. 
2. SOFTWARE ARCHITECTURES: POSSIBLE ALTERNATIVES 
The annotation tools that are available today are based essentially on two alternative architectures. The 
first possibility is to modify the behavior of the browser (see e.g. [COM]), so that after fetching a 
document, it allows writing notes that can be stored either locally or on a separated web server. Similarly, 
for every page it can enquiry the (local or remote) notes repository, and visualize existing notes with the 
document. The approach completely de-couples the original material from the notes. The choice of having 
the notes stored locally is of limited value, since it does not allow to interact with other people. The main 
problem of this approach is that modifying a browser is not a trivial task: the best solution could be one 
based on the notion of plug-in. However this would require maintaining different plug-ins for different 
browsers. 
The second major architecture is based on the concept of an “Annotation-server”. Examples of 
commercial services are [ANN] [THI]; a non-commercial instance is CritLink [CRI]. The idea is to have an 
intermediate web server (annotation server) that gets the requests, forwards them to the page server, gets 
the response and decorates it with the notes. Similarly, the annotation accepts the new notes and stores 
them. This architecture has some major advantages: it does not need a customized browser, and still 
preserves the separation between notes and content. The requested URL must be coded in a special way: 
“http://url_of_the_annotation_server?//http://url_of_the_resource”: the “real” URL is passed as a parameter 
to the annotation server. This can rather annoying, since every URL has to be “preprocessed” by the user in 
order to obtain the desired behavior. Moreover, following a link from a page does not pass through the 
annotation server, unless the server itself does take the burden of parsing all pages it delivers in order to 
suitably change all referenced URLs.  
A third approach (not found in literature) could be possible: the Annotation-server could be registered 
by the user as the standard proxy used by the browser. In such way all requests pass through the Annotation 
server, and the problem of explicitly coding the URL would be completely solved. This solution is simple, 
but it conflicts with the typical notion of a Proxy (a local  machine, typically used for optimizing the 
network traffic, and often employed also for by-passing a local firewall).  
By examining these architectures, one finds that the common denominator is the separation between the 
content server and the annotation server. This choice has obvious advantages: 
1. the content server needs not to be aware of the existence of the annotation server;  
2. one can define multiple annotation servers, supplying notes to (possibly closed) groups; 
3. it is possible to annotate just about every resource available on the web. 
However, the limited success of the existing system witnesses that problems overcome the advantages: 
some companies that o ffered an annotations as a commercial service discontinued their offering [THI]. 
We therefore think that it is worth revising the fundamental choices. In particular, we try to drop the 
nice but ambitious idea to be able to annotate any possible page. We focus on an e-learning platform that 
typically gets the (main) content from a limited number of servers (very often just one): our goal becomes 
therefore to be able to annotate only the pages of these servers. At this point, the separation between 
annotation server and content server becomes less relevant, and we can concentrate the whole job on the 
same server. This approach does not require a customized browser neither needs to pass through an 
intermediate server, relieving both problems encountered above. The last problem to be solved is to make 
the look and feel of the pages appealing, and to integrate the two functions (providing content and notes) in 
the same server. 
The solution we suggest is to add the annotation functionality to a web server as Java servlets [SER]. 
Servlets are platform independent, and are supported by virtually every Web Server available on the 
market. The servlet gets the request for a page, locally searches a database that stores the notes, and builds 
an annotated page that is served back to the user. Similarly, another servlet gets new notes and stored them 
in the database. The original page is almost unchanged: we only require that: 
1. It is written in valid XHTML (an HTML extension that is XML compliant)  
2. The page contains a definition of the contexts to which notes can be appended. 
The transformation from normal (even incorrect!) HTML to XHTML can be easily done by a free tool 
(Dave Raggett's HTML TIDY [TYD]). The definition of the contexts can be done automatically, with the 
chosen granularity: for instance each phrase, or each paragraph could be a context). 
The notes are rendered in place using the standard subset of JavaScript that is commonly recognized by 
the most diffused recent browsers. 
In summary, the architecture we provide contemplates: 
1. an (automatic) conversion of HTML pages to a suitable (XHTML) format 
2. the filtering of each request though a system based on servlets 
3. the storage of the notes on a database residing on the server that provides content. 
In addition, we introduce the notion of users and groups so that the visibility of the notes can be 
restricted to particular actors (a class, the teachers, on particular person etc.). Such addition reflects the 
spirit of supporting or particular domain of election, i.e. e-learning. 
2.1 Implementation: WebNotes 
To proof the concept, we implemented a tool called WebNotes according to the architecture we suggest. 
A first part of WebNotes is an automatic tool that performs the preprocessing of the page. During the 
conversion process the granularity of the markable context that can be annotated is chosen: it can be each 
word, each phrase or each paragraph. As we mentioned, the process is necessary in order to guarantee that 
the resulting pages are XHTML compliant, and that the contexts are suitably defined. (A context is a SPAN 
field: every SPAN field can contain one ore more notes). 
 The user requests pages to a servlet, which maintains a set of notes and their properties. Notes are 
shown in the text as tiny icons embedded in the page: when the user moves the mouse over the icon the 
note pops up. Public notes are visible to everybody. After the user identifies him/herself through a login 
process, s/he can see all notes allowed by her/his privileges. 
Users can toggle between two modes: browsing and editing. While browsing, when they move the 
mouse pointer over an icon that shows the presence of a note, the note pops up on place. When moving the 
mouse away the note disappears, unless it was stuck by the reader, in which case it disappears only when 
explicitly closed.  In order to edit the page (adding or modifying a note) the user enables editing mode and 
simply clicks on the location where s/he wants to add the note. A popup window appears, and the users can 
edit/modify the note. In the basic version the note contains only text, without any formatting. In an 
enhanced version of WebNotes, the window contains an applet that allows writing HTML in a “What-You-
See-Is-What-You-Get” fashion. We kept the applet separated in order to minimize the requirements we 
make on the browser, and in order to avoid delays related to its downloading. 
Tools for administrating the annotations, and for notifying new notes to the users are also included in 
WebNotes. 
Since WebNotes is made by a series of Java Servlets, it can be deployed on any Servlet-enhanced Web 
Server (nowadays virtually every serious Web Server can has a servlet-compliant engine). We do not 
assume any special requirement on the client side, the only request being the support of the standard subset 
of JavaScript.  
3. CONCLUSION 
Although much emphasis has been given to the support of collaboration via web since the early WWW 
years [COL], a convincing technology has not yet emerged. Interesting approaches run from an almost 
uncontrolled interactive editing of web pages (wiki’s [CUN]) to more controlled annotations. In particular, 
adding notes to a Web page is not a new idea per se. Tools comparable to what we present have been 
proposed in the past, but in most cases their architecture was dissimilar from the one we’ve chosen. The 
main architectural choices were either based on browser-specific tools, or on external mediator servers. A 
comparison of some available tools can be found in [GAR]. 
Our tool is based on an automatic pre-processing of an HTML page to include the fields that (with the 
chosen granularity) define the markable locations, relies on a basic browser and on a standard web-server 
architecture to deliver the content, and presents notes in a more friendly way. Also, our tool is more 
intimately linked to the processes typical of an e-learning system, and can be easily integrated with existing 
e-learning platforms. 
 
REFERENCES 
 
 
[ANN] http://www.annotate.net/ Annotate 
[AMA] Amaya, W3C's Editor/Browser, http://www.w3.org/Amaya/ 
[COL] “Collaboration, Knowledge Representation and Automatability” http://www.w3.org/Collaboration/ 
[CUN] Cunnigham, W.: wiki (wiki wiki web) http://c2.com/cgi/wiki?WikiHistory  
[CRI] CritLink  http://crit.org/http://crit.org/index.html  
[COM] ComMentor  http://hci.stanford.edu/commentor/ , by Martin Röscheisen, Christian Mogensen, and Terry 
Winograd at the Stanford Digital Library Project 
[KOI] Koivunen, M.R. et al., “The W3C Collaborative Web Annotation Project ... or how to have fun while building an 
RDF infrastructure”, UIST 2000, 
http://www.w3.org/2000/02/collaboration/annotation/papers/annotationinfrastructure  
[GAR] Garfunkel, J.,  “Web Annotation Technologies“, 
http://look.boston.ma.us/garf/webdev/annote/software.html  
[RDF] “Resource Description Framework”, http://www.w3.org/RDF/ 
[SER] “JavaTM Servlet Technology”   http://java.sun.com/products/servlet/ 
[THI] ThirdVoice http://www.thirdvoice.com/  Following the link, one discovers that: “As of April 2, 2001, we are 
no longer supporting the consumer version of the our search and annotation tools.” 
[TID] Tidy http://www.w3.org/People/Raggett/tidy/  
[XLI] XML Linking Language (XLink) Version 1.0, W3C Recommendation 27 June 2001, 
http://www.w3.org/TR/xlink/  
[XPO] XML Pointer Language (XPointer) Version 1.0, W3C Candidate Recommendation 11 September 2001, 
http://www.w3.org/TR/xptr/ 
 


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