We use logical symbols--entities--to express propositions--combination of entities--in a logical expression and carry out operations similar to those in numbers.　A proposition that contains a propositional connective, as "and" "or" "if", is called a compound proposition.
　A relationship (formed in a "binary" connective--mainly with "and") is a compound proposition.

　RULE: A "combination-table" shall be created through the combination of two resources.

　A "combination-table" is called "taisyo-hyo", that sounds like "tie-show-he-yo".

　An example:
　　employee: (employee-NO, employee-name,...)
　　division: (division-code, division-name,...)

　So, the combination-table (taisyo-hyo) comes as,
　the combination-talbe: (employee-NO(R), division-code(R))

　The "set-theory" mathematicians counter this argument by saying that it's a algorithm through "join" operation, not a table--they take it as data-redundancy.
　If so, they must not take a table of "inventory", because an "inventory" is a combination table among 3 resources--stockhouses, shelves and products.

　The combination-table of (employee-NO(R), division-code(R)) makes "implicitly" an event "assign".
　Put a date in the combination-table as in (employee-NO(R), division-code(R)| date)--it shows "explicitly" when who was assigned to which division.
　The definition of "event" is that a "thing" has an attribute of "date".　The combination-table has, therefore, the nature of "event"--but it has not any identifier, it's a "quasi-event".
　If and when we give the identifier of assign-NO, the combination-table makes an event (of assignment).

Note:
　All events are made from combination-tables, all events are subsets of combination-tables.
　Combination-tables are not exceptions to "events".