ERMine

ERMine is a library to parse text files describing a conceptual Entity Relationship model and create an object representation of this model.

Notation:

Entities

The name of an entity must be written between brackets: [ entity_name ]

Expl:

• [Customer]
• [Date and Time]
• [Country]

Attributes

Attributes must follow the name of the entity

[[ * | PK ] | [ ~ | PPK ]] attribute_name [ sql-type ] [ ? | NULL | ?? | SPARSE] [^ | IMMUTABLE] [ # | MV ] [ % | CALC ] [{% derived_formula %}] [ = | DEFAULT ] [{= default_formula =}]

Expl:

• firstName attribute firstName exists
• firstName varchar(50) attribute firstName is a varchar(50)
• email varchar(120)? attribute email is a varchar(120) and is nullable
• email varchar(120)?? attribute email is a varchar(120) and is sparse
• * customerNr char(10) attribute customerNr is a char(10) and is part of the primary key
• lastName varchar(50)^ attribute lastName is a varchar(50) and is immutable
• address varchar(250) # attribute address is a varchar(250) and must support multiple values
• fullName varchar(250) {% firstName + ' ' + lastName %} attribute fullName is derived and the formula is firstName + ' ' + lastName
• category char(1) {='A'=} attribute category has a default value equal to 'A'

Before the name of the attribute

Primary key is noted with a star (*). An alternative notation is "PK". Partial keys are noted with a tilt (~). An alternative notation is "PPK".

After the name of the attribute

• The sql-type of the attribute must follow the name of the attribute.
• Nullable attributes must postfix the sql-type with an question mark (?). An alternative notation is "NULL".
• Sparse attributes must postfix the sql-type with an question mark (??). An alternative notation is "SPARSE".
• Immutable attributes must postfix the sql-type with a circumflex accent (^). An alternative is the notation "IMMUTABLE"
• Multivalued attributes are noted with a cardinal (#). An alternative is the notation "MV"
• Derivated attributes are noted with a percentage (%). An alternative is the notation "CALC"
  • Formula for implementation of derivated attributes must be specified between the curly braces and percentages symbols ({% ... %})
• An attribute with a default value is noted with a equal (=). An alternative is the notation "DEFAULT"
  • Formula for implementation of default values must be specified between the curly braces and equal symbols ({= ... =})

Domains

<name_of_domain> first_value second_value ... last_value

A domain is a set of valid values for one or more attributes. A domain is defined with between angle brackets (<>) and the list of valid values is enlisted with one value by line. If a value contains many words then it should be written between quotes. At the moment, domains can only be a list of strings.

Expl:

<Weekday>
Monday
Tuesday
Wednesday
'Later in the week'

To specify that an attribute is enforced by a domain you must replace the sql-type by the name of the domain.

Expl:

[Restaurant]
* RestaurantCode varchar(20)
ClosingDay Weekday

In this example the ClosingDay of a restaurant is constrained to be one of the four values defined in the domain Weekday.

Relationships

first_entity_name [ ? | 1 | * | + ] - relationship_name - [ ? | 1 | * | + ] second_entity_name

for unary relationships the name of the first and second entities must be identical.

Ternary (or more) relationships are noted differently

relationship_name first_entity_name [ ? | 1 | * | + ] second_entity_name [ ? | 1 | * | + ] third_entity_name [ ? | 1 | * | + ]

Cardinalities

• ? stands for 0..1
• 1 stands for 1..1
• * stands for 0..*
• + stands for 1..n

Expl:

• [Customer] +-owns-1 [Account] a customer has one or more accounts and each account belongs to exactly one customer
• [City] 1-located-* [Country] a city is located in excatly one country and a country incorporates zero or n cities
• -located- [City]1 [Country]* a city is located in excatly one country and a country incorporates zero or n cities (alternate notation)
• -deal- [Vendor]+ [Customer]+ [Location]1 a deal involves many vendors and customers in a unique location.