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Section: New Results

Enumeration of Query Results

In many applications the output of a query may have a huge size and computing all the answers may already consume too many of the allowed resources. In this case it may be appropriate to first output a small subset of the answers and then, on demand, output a subsequent small numbers of answers and so on until all possible answers have been exhausted. To make this even more attractive it is preferable to be able to minimize the time necessary to output the first answers and, from a given set of answers, also minimize the time necessary to output the next set of answers - this second time interval is known as the delay. We have shown that this was doable with a almost linear preprocessing time and constant enumeration delay for first-order queries over structures having local bounded expansion [22].