  Each year the International Semantic Web Conference organizes a set of
Semantic Web Challenges to establish competitions that will advance
state-of-the-art solutions in some problem domains. The Semantic Answer Type
and Relation Prediction Task (SMART) task is one of the ISWC 2021 Semantic Web
challenges. This is the second year of the challenge after a successful SMART
2020 at ISWC 2020. This year's version focuses on two sub-tasks that are very
important to Knowledge Base Question Answering (KBQA): Answer Type Prediction
and Relation Prediction. Question type and answer type prediction can play a
key role in knowledge base question answering systems providing insights about
the expected answer that are helpful to generate correct queries or rank the
answer candidates. More concretely, given a question in natural language, the
first task is, to predict the answer type using a target ontology (e.g.,
DBpedia or Wikidata. Similarly, the second task is to identify relations in the
natural language query and link them to the relations in a target ontology.
This paper discusses the task descriptions, benchmark datasets, and evaluation
metrics. For more information, please visit https://smart-task.github.io/2021/.
