Chapter 9

The PACK and UNPACK Operators I: The Single-Attribute Case

This chapter and the next build on the notions introduced in the previous chapter—viz., expanded form and collapsed form, which apply to sets of intervals as such—to define two further canonical forms, viz., unpacked and packed form, which apply to relations with zero or more attributes of some interval type. The present chapter considers what’s probably the most important special case, viz., the case of unpacking or packing a relation on the basis of exactly one interval attribute. In particular, the usefulness of the two canonical forms, and the corresponding UNPACK and PACK operators, in dealing with the sample queries from Chapter 5 is clearly demonstrated.



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