THINK IN MODELS
OO
E-R vs. UML Class diagrams: What is the External/Internal Identifier implying?
In the post “The only thing I miss from the ER language”, Jordi stated a difference between E-R diagrams and UML Class diagrams, that is, the support of external identifiers by E-R and internal identifiers by UML, for identifying an instance of a type/class. I think it maybe appear as a little difference but, in … Continue reading
Relational Models and OO
Object-oriented theory and relational algebra Original: Zhang3, 2011-04-19 1. Relational algebra is a subset of first-order logic and what it represented is, the logical relationship between things. 2. E-R model has deviated from the real intention of relational logic. The ‘E’ should not be an entity but just a name. Relational modeling should not by … Continue reading
OO’ s Magic Cup
I believe, A real cup is an entity but, never an OO’ s object. Any classes are in your mind or your code but, not in the world. This expression sounds some vague, it could lead to questions, such as the following comments by Vhanniet. An improved version as follow: Any classes are in your … Continue reading
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