Metering Access to a Proprietary Data Base

Metering Access to a Data Base

Those practiced in Capability design may find it obvious that one can meter access to a data base. Yet it may be useful to go thru some exercises even for those with such experience. I will assume some familiarity with the fundamental Keykos facilities, primarily factories.

A requestor’s key to a factory provides an unlimited supply of identical objects that provide some service such as accessing data that may be proprietary. A particular object from a factory may be coded to limit the amount of service that it will provide. If the requestor’s key is available, however the user can always go back to get another object in order to get more service.

The first step to metered access is to imagine a vendor, which is a trusted, coin operated, front end to a factory that supplies instances on some condition such as paying. (There are several varieties of money possible in Keykos. It used to be a class exercise to invent and implement one. Here is one.) To maintain the current flexibility of the factory, it is must also vouch for the discretion of the factory, access to which it sells. It can do this by accepting another factory from the buyer and reporting the results of the factory discretion test. (In more detail, the vendor accepts a factory from the buyer called the tester here. The vendor tests the tester to verify that it a true factory and then asks the tester about its proprietary factory. This may sound arcane but it is actually tame compared with Hitchcock movies I have seen. Who knows what about whom?)

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