A number of additional operations on strings commonly occur in the formal theory.

He started to compose at this time with virtually no formal theory or composition training.

Many formal theories have been studied in the context of decidability.

However, strictly speaking, this is not the same as a formal theory of causality.

These have allowed him to, as he sees it, bypass the formal theory he never learned.

There is no formal theory for these, though numerous set sequences can be seen in professional play.

Over the past decade, work on formal theories of meaning for natural languages has developed very swiftly.

So far, empirical research from a life course perspective has not resulted in the development of a formal theory.

A formal theory is a set of sentences in a formal language.

Model theory studies the models of various formal theories.