Re: Entity and Identity
Date: Tue, 29 Sep 2009 10:56:22 +1000
Message-ID: <YWcwm.19098$tG1.3273_at_newsfe22.iad>
Bob Badour wrote:
>> * Value types (also known as lexical types). Because instances of
>> value types are identified by a lexical (written) form, the CQL
>> syntax encodes that, for example, "Name is written as String(20);"
>>
>> * Entity types (non-lexical types) of three forms:
>> * Subtypes, defined as for example "Employee is a kind of Person".
>> Here the identification is inherited from the first supertype.
>
> Sounds like the 1st Great Blunder to me. Why do you not have subtypes
> for value types? Subtyping is far more useful for value types than for
> structures.
I do. In the above example, Name is a subtype of String. All value types are either subtypes, or base types supported by some implementation framework. I don't support multiple inheritance for value types, and a value type cannot be derived from an entity tpe and vice versa.
> How is it truly relational with all these superfluous structural elements?
-- Clifford Heath, Data Constellation, http://dataconstellation.com Agile Information Management and DesignReceived on Tue Sep 29 2009 - 02:56:22 CEST