Veridicity

This paper addresses the problem of assessing the veridicity of textual content. Has an event mentioned in the text really occurred? Who is the source of the information? What is the stance of the author of the text? Does the author indicate whether he believes the source? We will survey some of linguistic conventions that indicate the author's commitment, or the lack thereof, to the propositions contained in her text. In particular we discuss phenomena that have been studied as presuppositions or conventional implicatures in previous literature. Some of those, such as factive and non-factive verbs, have received extensive attention in the past. Some others, such as supplemental expressions (e.g. appositives, parentheticals), have not received much previous attention, although they are very common and a rich source of textual inferences. A recent study by Christopher Potts classifies supplemental expressions as conventional implicatures. We agree with Potts on the label but not on what it means. In contrast to Potts, we claim that supplemental expressions cannot always be treated as the author's direct commitments and argue that they do not constitute a basis for a distinction between presuppositions and conventional implicatures. We illustrate some cases of conventional implicature and show how they indicate an author's commitment to the truth of his statements and briefly state the importance of these distinctions for Information Extraction (IE).