2 Added hyperlink to the book on Amazon so others can see the book being referenced

I'm currently reading "SQL and Relational Theory" by C.J. Date"SQL and Relational Theory" by C.J. Date. And although I'm quite far in the book, I've got a few basic questions. I want to know what the term "logical difference" means, The book does try to explain the term with examples, but does not really explain what it means (or maybe I'm understanding it wrong??)

Here is a small part from the book:

I've said that there's a logical difference between a relation and a picture of a relation. The concept of logical difference derives from a dictum of Wittgenstein's:

• All logical differences are big differences.

I know what a logical difference means intuitively, I know what the difference is between a relation and a picture of a relation. What I want is a formal-like definition of the concept of a "logical difference" so I have a good idea of what it means.

I'm currently reading "SQL and Relational Theory" by C.J. Date. And although I'm quite far in the book, I've got a few basic questions. I want to know what the term "logical difference" means, The book does try to explain the term with examples, but does not really explain what it means (or maybe I'm understanding it wrong??)

Here is a small part from the book:

I've said that there's a logical difference between a relation and a picture of a relation. The concept of logical difference derives from a dictum of Wittgenstein's:

• All logical differences are big differences.

I know what a logical difference means intuitively, I know what the difference is between a relation and a picture of a relation. What I want is a formal-like definition of the concept of a "logical difference" so I have a good idea of what it means.

I'm currently reading "SQL and Relational Theory" by C.J. Date. And although I'm quite far in the book, I've got a few basic questions. I want to know what the term "logical difference" means, The book does try to explain the term with examples, but does not really explain what it means (or maybe I'm understanding it wrong??)

Here is a small part from the book:

I've said that there's a logical difference between a relation and a picture of a relation. The concept of logical difference derives from a dictum of Wittgenstein's:

• All logical differences are big differences.

I know what a logical difference means intuitively, I know what the difference is between a relation and a picture of a relation. What I want is a formal-like definition of the concept of a "logical difference" so I have a good idea of what it means.