Simplifying filter/flow graphs by subgraph substitution

Although the filter/flow model is a useful concept for query visualization, the resulting graphs can be quite complex. We aim to reduce this complexity by substituting recurring subgraphs with more compact structures. Based on related work on extensions to the filter/flow concept, we have identified four recurring subgraphs that can be significantly simplified by substitutions. We describe these substitutions and discuss the preconditions that must be satisfied for their application. An example of news filtering illustrates how the substitutions can be used to simplify the overall structure of filter/flow graphs and increase their readability.