The Open Knowledge Extraction (OKE) challenge, at its second edition, has the ambition to provide a reference framework for research on Knowledge Extraction from text for the Semantic Web by re-defining a number of tasks (typically from information and knowledge extraction), taking into account specific SW requirements. The OKE challenge defines two tasks: (1) Entity Recognition, Linking and Typing for Knowledge Base population; (2) Class Induction and entity typing for Vocabulary and Knowledge Base enrichment. Task 1 consists of identifying Entities in a sentence and create an OWL individual representing it, link to a reference KB (DBpedia) when possible and assigning a type to such individual. Task 2 consists in producing rdf:type statements, given definition texts. The participants will be given a dataset of sentences, each defining an entity (known a priori). The following systems participated to the challenge: WestLab to both Task 1 and 2, ADEL and Mannheim to Task 2 only. In this paper we describe the OKE challenge, the tasks, the datasets used for training and evaluating the systems, the evaluation method, and obtained results.