“like” button on Facebook and “share” button on Twitter.” This way, the ArguBlogging tool uses familiar interaction styles to enable critical argumentation on the Web.

evaluating the Argument Web

The kind of continuous evaluation needed by the Argument Web involves usability in two distinct domains— public and academic—and expressivity and computational flexibility through metrics drawing on formal, computational methods, as well as on more pragmatic engineering principles.

In terms of raw usage through compatible tools (such as Rationale and Araucaria), the Argument Web today includes tens of thousands of users worldwide. The native applications (such as OVA) released in the past few years naturally involve fewer, but the core AIFdb includes more than 11,000 argument components, the second largest semantically rich argumentation dataset (after Debategraph), including in seven languages; for example, the Archelogos repository is fully imported into the Argument Web. More significant, the infrastructure and analysis tools have been used in at least seven research projects involving 10 labs in France, Poland, the U.K., and the U.S., each with different foci, including generative and analytical, multilingual and monolingual, and dialogical and monological.

In terms of expressivity, the Argument Web balances well-defined formal properties and pragmatic solutions to engineering problems; for example, the underlying ontology is demonstrably more expressive than one of the foremost formal accounts of defeasible argumentation, ASPIC+, 2 but a well-defined subset can be used to induce abstract frameworks on which evaluation can be performed. 16 Ongoing work in discourse analysis5 demonstrates that even rhetorically and linguistically sophisticated maneuvers (such as ad hominem argumentation) can be captured in the Argument Web. At the same time, formal description-logic analysis of the AIF ontology13 shows powerful abstractions can support advanced search and evaluation of arguments involving, say, specific schemes of presumptive reasoning.

to tease apart the structure of what is being said, directly inserting it into the Argument Web.

Direct discussion and mixed-ini-tiative argumentation. Direct discussion between two or more people on the Web takes place not just via email and instant messaging but also on forums and message boards. However, these technologies offer only the most basic of structural tools, and the inferential structure of an argument in a discussion is easily lost. The Web-based discussion software Arvina10 (see Figure 4) allows participants to debate a range of topics in real time in a way that is structured but at the same time is unobtrusive. Users can ask questions (such as “Do you agree?” and “Why do you think this is the case?”) of other participants in the discussion, as well as express their own agreement or disagreement with a particular point and provide supporting reasons for their views. Moreover, Arvina can use dialogue protocols to structure the discussion between participants.

Arvina can take on a multi-agent
system populated by agents repre-
senting authors whose opinions are
available on the Argument Web. It is
thus possible to question the partici-
pants of, say, past Moral Maze radio
programs about their opinions, and
agents representing participants can
be added to a discussion and ques-
tioned about what they think about
the topic discussed during the pro-
gram. An agent then answers by giv-
ing the opinions originally expressed
during the broadcast by a particular
participant. In this way people are able
to question any opinion expressed on
the Argument Web, whether originally
added through OVA, ArguBlogging, or
other tools.

Argument blogging. A final example of how argumentation technologies based on the Argument Web facilitates online debate concerns blogging, a highly popular form of online communication. If one wants to reply to an opinion presented somewhere on the Web in a blog, the usual way is to provide a simple hyperlink to the article or page in which the opinion is expressed. However, the resulting structure of supporting and competing opinions is easily lost due to lack of semantic information in the links.

We built a simple tool called ArguBlogging, for Argument Blogging, 10 to improve rational debate through this popular form of expressing opinions online. It ensures that, if desired, opinions on blogs and other webpages can be linked through the underlying infrastructure of the Argument Web, allowing users to agree or disagree with opinions anywhere on the Web, simultaneously posting it to their blog (connecting to two popular blogging platforms, Blogger and Tumblr) and adding it to the Argument Web; Figure 5 is the ArguBlogging window (or widget) rendered on a webpage, providing options for responding.

A typical blog post through ArguBlogging contains an “argue” button that, clicked, brings the widget onscreen. It allows users to respond to the blog post as a whole through ArguBlogging and is similar to the

figure 5. the ArguBlogging widget.