"Scientific workflows have been increasingly used in the last decade as an instrument for data intensive science. Workflows serve a dual function: first, as detailed documentation of the scientific method used for an experiment (i. e. the input sources and processing steps taken for the derivation of a certain data item), and second, as re-usable, executable artifacts for data-intensive analysis. Scientific workflows are composed of a variety of data manipulation activities such as Data Movement, data transformation, Data Analysis and Data Visualization to serve the goals of the scientific study. The composition is done through the constructs made available by the workflow system used, and is largely shaped by the function undertaken by the workflow and the environment in which the system operates. (...) This document specifies the classes and properties of the Workflow Motifs ontology, the OWL 2 encoding ot the aforementioned motif catalogue. The goal of this ontology is to provide the means to annotate workflows and their steps with the motifs of the vocabulary, without setting any restriction on how the workflows are defined themselves."