Formally, the phrase "encode more or less of the program logic as data" seems meaningless, as you cannot implement a Turing machine with static symbols alone. I

Formally, the phrase "encode more or less of the program logic as data" seems meaningless, as you cannot implement a Turing machine with static symbols alone. I feel the quoted phrase is intended to capture the idea that a suitable representation of the data can simplify the processing, but that is what is behind the point I am making. For example, in the case of an expert system, the data provides the specific facts of the domain and the logic is implemented by the program. In choosing to use an existing expert system engine, you have made a decision about how your system will go about achieving your goals, and that places significant constraints on how you should represent your data.