In this paper first we address the problem of predicting SPARQL query execution time. Accurately predicting query execution time enables effective workload management, query scheduling, and query optimization. We use machine learning techniques to predict SPARQL query execution time. We generate the training dataset from real queries collected from DBPedia 3.8 query logs. As features of a SPARQL query, we use the SPARQL query algebra operators and different basic graph pattern types that we generate by clustering the training SPARQL queries. We achieved high accuracy (coefficient of determination value of 0.84) for predicting query execution time. Second, we address the problem of suggesting similar SPARQL queries based on query history. Users often need assistance to effectively construct and refine Semantic Web queries. To assist users in constructing and refining SPARQL queries, we provide suggestions of similar queries based on query history. Users can use the suggestions to investigate the similar previous queries and their behaviors.
