DenseZDD: A Compact and Fast Index for Families of Sets

In many real-life problems, we are often faced with manipulating families of sets. Manipulation of large-scale set families is one of the important fundamental techniques for web information retrieval, integration, and mining. For this purpose, a special type of binary decision diagrams (BDDs), called Zero-suppressed BDDs (ZDDs), is used. However, current techniques for storing ZDDs require a huge amount of memory and membership operations are slow. This paper introduces DenseZDD, a compressed index for static ZDDs. Our technique not only indexes set families compactly but also executes fast member membership operations. We also propose a hybrid method of DenseZDD and ordinary ZDDs to allow for dynamic indices.