Chapter 5

What’s the Problem?

In a nutshell, the problem of temporal data is that it quickly leads to constraints and queries (and updates) that are unreasonably complex to express—unreasonably complex, that is, unless the system provides some well designed shorthands, which commercially available DBMSs typically don’t. This chapter illustrates this fact by, first, considering a simple nontemporal database and certain simple constraints and queries on that database; second, “semitemporalizing” that database by introducing appropriate “since” attributes and investigating what happens to those constraints and queries on that semitemporal version of the database; and, third and last, “fully temporalizing” the database by introducing appropriate “from” ...

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