Open Knowledge Extraction (OKE) is the process of extracting knowledge from text and representing it in formalized machine readable format, by means of unsupervised, open-domain and abstractive techniques. Despite the growing presence of tools for reusing NLP results as linked data (LD), there is still lack of established practices and benchmarks for the evaluation of OKE results tailored to LD. In this paper, we propose to address this issue by constructing RDF graph banks, based on the definition of logical patterns called OKE Motifs. We demonstrate the usage and extraction techniques of motifs using a broad-coverage OKE tool for the Semantic Web called FRED. Finally, we use identified motifs as empirical data for assessing the quality of OKE results, and show how they can be extended trough a use case represented by an application within the Semantic Sentiment Analysis domain.