Module Database.ERD

Exported datatypes:

Data type to represent entity/relationship diagrams. The components are the name of the ER model, the list of entities, and the list of relationships.

Constructors:

• ERD :: ERDName -> [Entity] -> [Relationship] -> ERD

The name of an ER model (a string).

Type synonym: ERDName = String

Data type to represent the entities of an ER model. Each entity consists of a name and a list of attributes.

Constructors:

• Entity :: EName -> [Attribute] -> Entity

The name of an entity (a string).

Type synonym: EName = String

Data type to represent attributes of entities of an ER model. Each attribute consists of

• a name
• the domain (i.e., type) of the attribute
• a value specifying the key property of thi attribute (no key, primary key, or unique)
• a flag indicating whether this attribute can contain null values

Constructors:

• Attribute :: AName -> Domain -> Key -> Null -> Attribute

The name of an attribute (a string).

Type synonym: AName = String

Data type to represent key properties of attributes (no key, primary key, or unique).

Constructors:

• NoKey :: Key
• PKey :: Key
• Unique :: Key

Type of the flag of an attribute indicating whether the attribute can contain null values (if the flag has value True).

Type synonym: Null = Bool

Data type the domain of an attribute. If the attribute has a default value, it can be specified as an argument in the domain.

Constructors:

• IntDom :: (Maybe Int) -> Domain
• FloatDom :: (Maybe Float) -> Domain
• CharDom :: (Maybe Char) -> Domain
• StringDom :: (Maybe String) -> Domain
• BoolDom :: (Maybe Bool) -> Domain
• DateDom :: (Maybe CalendarTime) -> Domain
• UserDefined :: String -> (Maybe String) -> Domain
• KeyDom :: String -> Domain

Data type to represent the relationships of an ER model. Each relationship consists of a name and a list of end points (usually with two elements).

Constructors:

• Relationship :: RName -> [REnd] -> Relationship

The name of a relationship (a string).

Type synonym: RName = String

An end point of a relationship which consists of the name of an entity, the name of the role, and a cardinality constraint.

Constructors:

• REnd :: EName -> Role -> Cardinality -> REnd

The name of a role (a string).

Type synonym: Role = String

Cardinality of a relationship w.r.t. some entity. The cardinality is either a fixed number (e.g., (Exactly 1) representing the cardinality (1,1)) or an interval (e.g., (Between 1 (Max 4)) representing the cardinality (1,4), or (Between 0 Infinite) representing the cardinality (0,n)).

Constructors:

• Exactly :: Int -> Cardinality
• Between :: Int -> MaxValue -> Cardinality

The upper bound of a cardinality which is either a finite number or infinite.

Constructors:

• Max :: Int -> MaxValue
• Infinite :: MaxValue

Exported operations: