Wednesday, August 30, 2023


“A set is an identification of zero or more objects (elements, entities, depending on context) that can be referred to as a group by name (usually a symbol) and which are drawn from some pre-defined universe of objects. Such objects are then said to be the members of the set. The set members have one or more properties in common. It is, however, possible that the sole defining property of a set can be simply that the definer of a set has explicitly designated as members certain (one or more) objects that do not share any properties, so the only property shared by the set members is the designation property (DP) -- each member then has the property of having been designated member of the set. More explicitly, for any set, an assertion of set membership has definitional priority over the necessity of any other properties being shared among the members.” --David McGoveran

Thus, members of a set are "drawn from some pre-defined universe of objects" on the basis of shared properties (that define their type and are required for set membership) -- if nothing else, at least a designation property (DP). These properties distinguish members of the set from those in the universe that are not.

Thursday, August 17, 2023


Note: This a revision of an earlier post

RDM is an application to database management of mathematical relation theory (MRT) consistent with simple set theory (SST) expressible in first order predicate logic (SST/FOPL) that is used to formalize symbolically conceptual models of reality as logical models for database representation.

In RDM a domain can "appear" in multiple relations: the domain represents an abstract property, attributes defined on it represent that property in contexts of specific entity groups that relations represent. For example, attribute SALARY in relation EMPLOYEES represents the property represented by domain MONEY in the context of entities of type Employee and attribute BUDGET in relation DEPARTMENTS represents it in the context of entities of type Department.

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