“…The for-mer systems allow users to pose a free text question (or just a set of keywords) and then interpret the input as a formal query. Such systems include FALCON [15], AquaLog [82], AutoSPARQL [83], QuestIO [84], Siemens' query system [85], and SPARK [16]. Systems in the second group, such as Quelo [17], allow for natural language expressions to be used at each step during query construction.…”