Compact Argumentation Frameworks

Abstract argumentation frameworks (AFs) are one of the most studied formalisms in AI. In this work, we introduce a certain subclass of AFs which we call compact. Given an extension-based semantics, the corresponding compact AFs are characterized by the feature that each argument of the AF occurs in at least one extension. This not only guarantees a certain notion of fairness; compact AFs are thus also minimal in the sense that no argument can be removed without changing the outcome. We address the following questions in the paper: (1) How are the classes of compact AFs related for different semantics? (2) Under which circumstances can AFs be transformed into equivalent compact ones? (3) Finally, we show that compact AFs are indeed a non-trivial subclass, since the verification problem remains coNP-hard for certain semantics.Comment: Contribution to the 15th International Workshop on Non-Monotonic Reasoning, 2014, Vienn

Focus Triggers and Focus Types from a Corpus Perspective

The article discusses several issues relevant for the annotation of written and spoken corpus data with information structure. We discuss ways to identify focus top-down (via questions under discussion) or bottom-up (starting from pitch accents). We introduce a two-dimensional labelling scheme for information status and propose a way to distinguish between contrastive and non-contrastive information. Moreover, we take side in a current debate, claiming that focus is triggered by two sources: newness and elicited alternatives (contrast). This may lead to a high number of semantic-pragmatic foci in a single sentence. In each prosodic phrase there can be one primary focus (marked by a nuclear pitch accent) and several secondary foci (marked by weaker prosodic prominence). Second occurrence focus is one instance of secondary focus