Abstract According to a standard story, part of what we have in mind when say that an argument is valid it necessarily truth ‐ preserving : if the premises are true, conclusion must also be true. But—the story continues—that's not enough, since ‘Roses red, therefore roses coloured’, for example, while may truth‐preserving, so virtue form. Thus arrive at contemporary characterisation validity: N...

The large literature on costly signaling and the somewhat scant literature on preference signaling had varying success in showing the effectiveness of signals. We use a field experiment to show that even when everyone can send a signal, signals are free and the only costs are opportunity costs, sending a signal increases the chances of success. In an online dating experiment, participants can a...

In this article we present RoSeS (Really Open Simple and Efficient Syndication), a generic framework for content-based RSS feed querying and aggregation. RoSeS is based on a data-centric approach, using a combination of standard database concepts like declarative query languages, views and multi-query optimization. Users create personalized feeds by defining and composing content-based filterin...