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0 pointstriska6y ago0 comments

Related to the logical view, it would also be great to include deductive databases:

https://en.wikipedia.org/wiki/Deductive_database

Deductive databases derive logical consequences based on facts and rules.

Datalog and its superset Prolog are notable instances of this idea, and they make the connection between the relational model and predicate logic particularly evident.

Codd's 1979 paper Extending the Database Relational Model to Capture More Meaning contains additional information about this connection. For example, quoting from Section 3 Relationship to Predicate Logic:

"We now describe two distinct ways in which the relational model can be related to predicate logic. Suppose we think of a database initially as a set of formulas in first-order predicate logic. ..."

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mitchtbaum6y ago

It seems these rules refine the data outside the database itself. But they're so tightly integrated between the database and the application that the lines separating them become blurred.

triskaOP6y ago

Interestingly, when defining pure relations in Prolog, there is no "outside the database itself":

Both rules and facts are instances of a single unifying language element, a logical clause, which is also terminology from predicate logic.

This is useful from a conceptual perspective, and also for performance: Many automatic optimizations that deductive database systems perform apply equally to facts and rules. For instance, argument indexing is a notable feature of virtually all Prolog systems. It is similar to indices in relational databases, and can replace a linear scan of the knowledge base with a fast hash-based lookup that is performed in O(1).

mitchtbaum6y ago

> Both rules and facts are instances of a single unifying language element, a logical clause, which is also terminology from predicate logic.

Yeah; I'd like to see these general application layers more seamless and united in simple semantic units.

Like a higher level abstraction over code block elements, database record structures, and configuration setting ensambles; simply as phrases (..??) ....

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0 pointstriska6y ago0 comments

Related to the logical view, it would also be great to include deductive databases:

https://en.wikipedia.org/wiki/Deductive_database

Deductive databases derive logical consequences based on facts and rules.

Datalog and its superset Prolog are notable instances of this idea, and they make the connection between the relational model and predicate logic particularly evident.

0 comments

mitchtbaum6y ago

It seems these rules refine the data outside the database itself. But they're so tightly integrated between the database and the application that the lines separating them become blurred.

triskaOP6y ago

Interestingly, when defining pure relations in Prolog, there is no "outside the database itself":

Both rules and facts are instances of a single unifying language element, a logical clause, which is also terminology from predicate logic.

mitchtbaum6y ago

> Both rules and facts are instances of a single unifying language element, a logical clause, which is also terminology from predicate logic.

Yeah; I'd like to see these general application layers more seamless and united in simple semantic units.

Like a higher level abstraction over code block elements, database record structures, and configuration setting ensambles; simply as phrases (..??) ....

1 more reply

j / k navigate · click thread line to collapse