Syntropy - Type View

Basic Notation

Associations

Association multiplicity adornments
Symbol	Name	Placement	Restrictions	Comment
(none)	Single	Destination	Exclusive with Multiple and Optional	Constrains multiplicity of the dest. to be exactly one. Navigating the association yields an object of the destination type
	Multiple	Destination	Exclusive with Single and Optional	Constrains multiplicity of the destination to be zero or more. Navigating the association yields a collection of objects of the destination type
	Optional	Destination	Exclusive with Single and Multiple	Constrains multiplicity of the destination to be zero or one. Navigating the association yields an object of the destination type or nil
[m..n]	Range	Destination	Used only with Multiple	Constrains multiplicity of the destination to be in range m to n
[m]	Range	Destination	Used only with Multiple	Constrains multiplicity of the destination to equal m
[m+]	Range	Destination	Used only with Multiple	Constrains multiplicity of the destination to be in range m to infinity

Ordering adornments on multiple associations
Symbol	Name	Placement	Comment
(none)	Set	Destination	Destination collection is unordered, with no duplicates
[bag]	Bag	Destination	Destination collection is unordered, but with duplicates allowed
[seq]	Sequence	Destination	Destination collection is ordered
[...]	Sorted	Destination	Destination collection is sorted according to some predicate. A rigorous predicate has the form: [a, b: Type; expression] where a comes before b if the expression is true

Other adornments
Symbol	Name	Placement	Restrictions	Comment
	Qualifier	Source	Normally replaces a multiple	Defines a function, q, that selects from a multiple association using a parameter of type T. The destination can still be multiple, indicating that the parameter selects more than one object. If the function is not total over T, the destination should be optional
	Aggregation	Source	(none)	Fixes source membership of an association for the life-time of the destination. The life-time of the destination is contained within the life-time of the source. If the source is destroyed, the destination is destroyed
/	Derived	Anywhere on line, going across it	(none)	This association is logically derivable from others. Normally accompanied by a derivation expression
	Visible	Destination	Implementation model only	The association is definitely navigable from the source to the destination
?	Undefined	Destination	No other adornments allowed	The association from source to destination is not fully defined
X	Blocked	Destination	No other adornments allowed	The association is not navigable from source to destination

Constraints between associations
Constraints between associations are shown by drawing a dashed or faint arrow
Constraint	Meaning
	The membership of the destination association at the tail of the arrow is a subset of the membership of the destination association at the head of the arrow. The linked associations must have a common source
	Equivalent to subset of but used when the association at the tail of the arrow identifies a single object
	The association at the tail of the arrow is redefining the inherited association at the head

Special invariants
These special invariants appear in type boxes to constrain the values of properties
Invariant	Meaning
abstract	There can be no objects that conform to this type without also conforming to a sub-type of this type
const property	The value of this property is fixed throughout the life-time of each object conforming to this type
optional property	This property can take the value nil
sync	This type provides the non-exclusive contract with clients, and so guarantees not to raise wrongState exceptions, but may block callers (Implementation model only)
unique property	The value of this property will be different for every object in the model conforming to this type
value	This type is a value type, and so can have no navigable associations coming from it

Specification models

Implementation models

Synchronising types have another heading, Sync:, where expressions controlling the availability of operations are listed. A synchronising expression has the general form: