This paper describes the processes and issues of annotating event nuggets based on DEFT ERE Annotation Guidelines v1.3 and TAC KBP Event Detection Annotation Guidelines 1.7. Using Brat Rapid Annotation Tool (brat), newswire and discussion forum documents were annotated. One of the challenges arising from human annotation of documents is annotators' disagreement about the way of tagging events. We propose using Event Nuggets to help meet the definitions of the specific type/subtypes which are part of this project. We present case studies of several examples of event annotation issues, including discontinuous multi-word events representing single events. Annotation statistics and consistency analysis is provided to characterize the interannotator agreement, considering single term events and multi-word events which are both continuous and discontinuous. Consistency analysis is conducted using a scorer to compare first pass annotated files against adjudicated files.

In this paper, we describe the event nugget annotation created in support of the pilot Event Nugget Detection evaluation in 2014 and in support of the Event Nugget Detection and Coreference open evaluation in 2015, which was one of the Knowledge Base Population tracks within the NIST Text Analysis Conference. We present the data volume annotated for both training and evaluation data for the 2015 evaluation as well as changes to annotation in 2015 as compared to that of 2014. We also analyze the annotation for the 2015 evaluation as an example to show the annotation challenges and consistency, and identify the event types and subtypes that are most difficult for human annotators. Finally, we discuss annotation issues that we need to take into consideration in the future.