A basic relation contains two entities and a line showing the relation between them.
Example: Declaring Object Relations
@startuml
'Example: Declaring Object Relations
'Declare two objects.
object Object01
object Object02
'Create a relation between the two object.
Object01 - Object02
@enduml
Parts of Relations
Relations are comprised of three parts. Label is the only optional part.
entity - the object for which a relation can be described in an object diagram, must have two
connection - visual description of the relation between entities
label - textual description of the relation between entities
Entities
The connected entities can be objects, fields, map tables, cells, or packages. Objects, map tables, and packages are defined by their name. Fields and cells are defined by the parent object name followed by two colons (::) and the field or cell text.
object
field
map table
cell
package
Example: Relation Entities
@startuml
'Example: Relation Entities
'Create two objects with fields.
object Object01 {
Field01
}
object Object02 {
Field02
}
'Create a map table with two cells.
map MyMapTable {
Cell01 => Cell02
}
'Create a relation between the two objects.
Object01 - Object02
'Create a relation between the second object and a cell in the map table.
Object02 - MyMapTable::Cell01
@enduml
Labels
This text describes the relation between the connected entities. You can format labels with creole syntax for emphasis and markup language for color and emphasis. You can define colors with a standard color name or hex code. Labels are not required.
Example: Relation Labels
@startuml
'Example: Relation Labels
'Create three objects.
object Object01
object Object02
object Object03
'Create a relation between the first two objects.
'Use a label to explain that relation.
'Use creole to emphasize the text.
Object01 - Object02 : **Relation** //Text//
'Create a relation between the second two objects.
'Use a label to explain that relation.
'Use markup to add color and emphasis to the text.
Object02 - Object03 : <color #561D5E><b>Relation</b> <i>Text</i></color>
@enduml
Connections
The connection is the line between the entities. It can carry a lot of information. The only required portion of the connection is the dash (-) between the entities.
arrowhead - determines the shape of the arrow head, one may be on each end of the connection
line_type - determines the type of line between the entities
line_orientation - determines the direction of the second entity in relation to the first entity
line_color - determines the color of the line making the connection
line_thickness - determines the thickness of the line between the entities
Arrowheads
The connection can have an arrowhead on both ends. It must touch the dash that defines the connection.
Note: The following example will be shown with two dashes in the code to provide better aesthetics for the example image. See line orientation for further explanation.
Line_orientation determines the placement of an entity in relation to the connected entity. There are two options, default and relative directions.
Default
By default a single dash in the connection draws the relationship horizontally. Two dashes draws the relationship vertically. These are read left to right and then drawn from left to right and top to bottom.
Example: Line Orientation Default
@startuml
'Example: Line Orientation Default
'Create Five Objects
object Center
object Right
object Left
object Up
object Down
'Create relationships that point in all four directions.
'Use the default method.
Center - Right
Left - Center
Center -- Down
Up -- Center
@enduml
Relative Directions
Relative directions are defined by always using two dashes for the connection and writing the relative direction between the dashes. These are read from left to write and then drawn in the relative direction.
Example: Line Orientation Relative Directions
@startuml
'Example: Line Orientation Relative Directions
'Create Five Objects
object Center
object Right
object Left
object Up
object Down
'Creat relationships that point in all four directions.
'Use relative directions.
Center -right- Right
Center -left- Left
Center -down- Down
Center -up- Up
@enduml
Line Types
The line_type can change the connecting line to dashed or dotted. Line_type is placed inside of square brackets inside of the connecting dashes. Line_type, line_color and line_thickness can be placed in any order inside of the square brackets they are separated by commas.
Example: Line Types
@startuml
'Example: Relation Line Types
'Create three objects.
object Object01
object Object02
object Object03
'Create a relation between the first two objects.
'Make the connection dashed.
Object01 -[dashed] Object02
'Create a relation between the first two objects.
'Make the connection dotted.
Object02 -[dotted]- Object03
@enduml
Line Colors
The line_color changes the connecting line's color. Line_color is placed inside of square brackets inside of the connecting dashes with a hash symbol (#) before the color. You can define colors with a standard color name or hex code. Line_type, line_color and line_thickness can be placed in any order inside of the square brackets they are separated by commas.
Example: Line Colors
@startuml
'Example: Relation Line Colors
'Create three objects.
object Object01
object Object02
object Object03
'Create a relation between the first two objects.
'Make the connection dashed.
Object01 -[#009EA1] Object02
'Create a relation between the first two objects.
'Make the connection dotted.
Object02 -[#darkcyan]- Object03
@enduml
Line Thickness
The line_thickness changes the connecting line's width. Line_thickness is placed inside of square brackets inside of the connecting dashes. Line_type, line_color and line_thickness can be placed in any order inside of the square brackets they are separated by commas.
Example: Line Thickness
@startuml
'Example: Relation Line Thickness
'Create three objects.
object Object01
object Object02
object Object03
'Create a relation between the first two objects.
'Make the connection dashed.
Object01 -[thickness=4] Object02
'Create a relation between the first two objects.
'Make the connection dotted.
Object02 -[thickness=8]- Object03
@enduml
Association objects can be used to show many to one relations. The association object is a diamond.
Example: Association Objects
@startuml
'Example: Association Objects
'Create three objects.
object Object01
object Object02
object Object03
'Create an association object.
diamond Association01
'Create a relations between the first two objects and the association object.
Object01 --> Association01
Object02 --> Association01
'Create a relation between the association object and the third object.
Association01 --> Object03
@enduml
