______ is the special attribute value that indicates an unknown or missing value.

_________ is a collection of all entity instances of a particular entity type.

_________ is a conceptual entity that is meant to express the various categories of accounts in accounting system.

____________ involves the technique of collecting, sorting, relating, interpreting and computing data items.

__________ is a process of refining  a database design through which the possibility of duplicate or redundant data items is reduced or eliminated.

The major elements of _________ are entities, attributes, identifiers and relationships that are used to express a reality for which a database is to be designed.

A ____________ is a set of indivisible values.

The values of attributes of an entity belonging to entity type are known as _____

_________ is a conceptual entity that is meant to express various accounts, each of which belongs to a particular category of accounts.

___________ is an association of entities where the association includes one entity from each participating entity type.