Seminars - Friday Talk

Friday Talk - 5 April 2013

April 5th 2013

An institute meeting will take place on Friday 5th April  at 3pm in the Main Conference Room. Maulik Kamdar will give the presentation.

SEMGEL, a semantic technology based data analysis tool

March 8th 2013

Semgel is a web app to gather and analyze data from a selection of public websites.

Institute Meeting - Friday 1st February

February 1st 2013

This talk will give a short overview of the project with its major findings and outcomes, as well as briefly discuss future directions.

Lessons learned from a decade of deployed Semantic Web apps

October 21st 2011

As the Semantic Web vision was conceived in 2001, it is now entering its teen years.
What have we learned, when we look back on a decade of developing and deploying Semantic Web applications?
This talk will summarise the state of the art both for newcomers to the Web of Data, as well as for experts.
All findings are based on empirical evidence. First the talk will summarise an empirical survey of Semantic Web applications.
In addition, a conceptual architecture for Semantic Web apps will be introduced.
Finally the biggest implementation challenges, and approaches for making development for the future Web of Data easier, will
be discussed.

Measuring User Influence in Twitter: The Million Follower Fallacy

September 15th 2010

Directed links in social media could represent anything from intimate friendships to common interests, or even a passion for breaking news or celebrity gossip. Such directed links determine the flow of information and hence indicate a user's influence on others - a concept that is crucial in sociology and viral marketing. In this paper, using a large amount of data collected from Twitter, we present an in-depth comparison of three measures of influence: indegree, retweets, and mentions. Based on these measures, we investigate the dynamics of user influence across topics and time. We make several interesting observations. First, popular users who have high indegree are not necessarily influential in terms of spawning retweets or mentions. Second, most influential users can hold significant influence over a variety of topics. Third, influence is not gained spontaneously or accidentally, but through concerted effort such as limiting tweets to a single topic. We believe that thes

e findings provide new insights for viral marketing and suggest that topological measures such as indegree alone reveals very little about the influence of a user.

Evaluating Top-k Queries over Incomplete Data Streams

November 11th 2009

In this talk we will look into the problem of processing continuous top-k queries over multiple non-synchronized streams. Assuming a sliding window model, this general problem has been a well addressed research topic in recent years. Most approaches, however, assume synchronized streams where all attributes of an object are known simultaneously to the query processing engine. In many streaming scenarios though, different attributes of an item are reported in separate non-synchronized streams which do not allow for exact score calculations. We show how the traditional notion of object dominance changes in this case such that the k dominance set still includes all and only those objects which have a chance of being among the top-k results in their life time. Based on this, we propose an exact algorithm which builds on generating multiple instances of the same object in a way that enables efficient object pruning.

We show that even with object pruning the necessary storage for exact evaluation of top-k queries is linear in the size of the sliding window. As data should reside in main memory to provide fast answers in an online fashion and cope with high stream rates, storing all this data may not be possible with limited resources. We present an approximate algorithm which leverages correlation statistics of pairs of streams to evict more objects while maintaining accuracy and conclude the talk by reporting on an experimental evaluation.

SWSE Books Dataset: a Benchmark Dataset for a Comparative Evaluation of Semantic Browsing

July 18th 2008

Evaluating a semantic web search engine raises unique challenges: how to build a procedure that will evaluate the user interface without being biased by the dataset?
Contrary to most scientific fields, the reasearch area of user interfaces for the semantic web does not have any standard evaluation method (yet).

In this talk we will present how we built a benchmark dataset about books from different sources, how we dealt with merging the data, the issues encountered, and the solutions we came up with. We will then present the evaluation protocol, the tasks and the measures that we hope will be used soon for the evaluation of SWSE's user interface.