What Edgar Codd did not solve in RM / T - the third part
Date: Thu, 2 Aug 2018 01:52:55 -0700 (PDT)
Message-ID: <335277ae-a088-4b17-ab02-a9ee1e03e902_at_googlegroups.com>
In this post I will write about the insufficient knowledge of semantics in Codd's papers.
In RM / T model, Codd introduces the entity as the main term. Codd
associates the following two important concepts with the entity:
(i) Surrogate key
(ii) Relations
What is surprising in Codd's paper RM / T is that Codd did not define the
entity, i.e. Codd did not define the object.
I have presented Frege's letter to Russell on this user group.
(See my thread under the following headline: " Is Russell's paradox in fact fraud?") :
„Frege replied to Russell on June 22, 1902. In Frege's letter to Russell, there is the following part of the text: „Incidentally, it seems to me that expression „a predicate is predicated of itself“ is not exact. A predicate is as a rule a first-level function, and this function requires an object as argument and cannot have itself as argument (subject).“
Frege's text clearly defines the semantic role of the entity (object) in the predicate. This link between the object and the predicate (according to Frege) gives the proposition. Now, the matter is in the propositional logic, that is, we have the following question: is this proposition true or false. In fact, in this letter Frege presented this procedure in a short form. In Frege's theory, the entity is at a mental level. That's why the name of the object should be here. Therefore, the name of the object should be placed in the predicate, not the object. Unlike an object, the predicates and names are at the linguistic level.
Edgar Codd believed that relational database has „close relationships with
first-order predicate logic.“
In my opinion semantics is much more important for databases than the
"the first order predicate logic".
Frege's semantic theory is one of the most significant scientific discoveries in the history of science. In databases, the fundamental question is connecting abstract objects from databases to real objects in the real world. Schematically presented, we have the following:
Man -- Semantics -- Real World
------------------------------------------------
In my opinion, Codd is not even familiar with Frege's semantic theory. Codd never mentioned Frege, nor Frege's theory and results. In my paper "Database design and data model based on concept constructs and knowledge constructs" for the first time, the database solution based on Frege's theory was presented. I applied Frege's theory in the form presented by John Burgess from Princeton University.
Once again I will show an example with the use of my semantic procedures
which connects entity with its states.
In my data model I use the "identifier of the entity" and "the identifier of
the state of an entity". The word „identifier“ suggests that the identifier
can identify the entity in the database and in the real world.
The identifier of the state of an entity determines the state of the entity
in the database.
The identifier of the state of an entity with the help of the identifier of the entity can determine the state of the real object from the real world. The identifier of the state of an entity has data that belong to the real world entity and this identifier also has data that belong to the data from „picture“ of the real world entity. This „picture“ is in database's memory. These two identifiers I presented on this user group in 2005 and also on my web page www.dbdesign10.com
The surrogate key challenges the foundations of semantics. If someone is relying on semantics of the surrogate key, then you can not determine the real object. For example, if you are a car dealer and if the buyer has paid a car, then you can not tell the buyer the following: This on the screen is the surrogate key of your car. Go to the parking lot and take your car.
However, If someone paste the label which has surrogate key on the corresponding car, then this is no longer a surrogate key.
Vladimir Odrljin Received on Thu Aug 02 2018 - 10:52:55 CEST