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Learn more about the collection functions EXISTS, EACH, ALL, COLLECT FROM WHERE, COLLECT FROM NAMED WHERE, COLLECT, UNPACK, LIST, SIZE, UNIQUE, SUBSET OF, UNION, INTERSECTION, DIFFERENCE, SYMMETRIC_DIFFERENCE.

Overview

Function	Description
`EXISTS`	Determines whether an instance of a specified entity exists, optionally meeting certain criteria.
`EACH`	Determines whether all instances of a specified entity meet a certain criteria.
`ALL`	Creates a collection of all instances of a specified entity.
`COLLECT FROM [WHERE]`	Creates a collection of entity or attribute instances (meeting certain criteria).
`COLLECT FROM NAMED [WHERE]`	Version of COLLECT FROM [WHERE] for complex nested selections with an alias.
`UNPACK`	Extracts the value from a single valued collection or list. Is the inverse of the LIST function.
`LIST`	Creates a list based on a value. Is the inverse of the UNPACK function.
`SIZE`	Determines the size of a collection.
`UNIQUE`	Filters duplicate items from a collection resulting from a subexpression in a larger expression.
`SUBSET OF`	Returns `TRUE` if the items in a collection are all present in another collection.
`UNION`	Adds two collections of the same base type to a new collection.
`INTERSECTION`	Determines the intersection of two collections.
`DIFFERENCE`	Determines the difference between 2 collections. Returns

Table of Contents

minLevel	2

SIZE

This function determines the size of a collection.

Syntax

Code Block
SIZE ( collection )

collection - A collection of attribute or entity instances. This can be an expression or a relation attribute for instance.

Return type

integer

Example

Suppose you have a Parent and a Child entity, where Parent has a multivalued relation with Child via the relation Parent.has_Children. With this model the following instances are created:

...

Then:

if Parent_1 is active, SIZE ( Parent.has_Children ) = 3
if Parent_2 is active, SIZE ( Parent.has_Children ) = 1
without an active Parent instance, SIZE ( Parent.has_Children ) results in an error
if Child_1 is active, SIZE ( Child.hobbies ) = 2
if Child_3 is active, SIZE ( Child.hobbies ) = 3
if Child_4 is active, SIZE ( Child.hobbies ) = 1
SIZE ( ? ) = 0

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type	note

COUNT and SIZE are similar except for UNKNOWN: COUNT ( ? ) = UNKNOWN

UNIQUE

The UNIQUE function filters duplicate items from a collection. An expression resulting in a collection, never contains duplicate values. A subexpression however, can contain duplicates.

Syntax

Code Block
UNIQUE ( collection )

collection - A collection of attribute or entity instances.

Examples

Suppose the following model.

...

COLLECT Person.name FROM ALL Person = "Kim”, “Rick”, “Bob” (a result never contains duplicate values)
SIZE ( COLLECT Person.name FROM ALL Person ) = 4 (a subexpression can contain duplicate values)
SIZE ( UNIQUE ( COLLECT Person.name FROM ALL Person ) ) = 3 (the collection holds three unique values)

SUBSET OF

This function returns TRUE if the items in a collection are all present in another collection.

Syntax

Code Block
collection1 SUBSET OF collection2

collection1 - The collection that is tested to be a subset of the second collection.
collection2 - The collection that is tested to hold all the items in the first collection.

Return type

boolean

Examples

('a', 'b', 'c') SUBSET OF ('a', 'b', 'c', 'd') = TRUE
('a', 'b', 'c', 'd') SUBSET OF ('a', 'b', 'c') = FALSE
(Person.hobbies) SUBSET OF ([“Tennis”, “Soccer”, “Music”]) = TRUE if Person.hobbies = “Tennis”, “Soccer”
(Person.hobbies) SUBSET OF ([“Tennis”, “Soccer”, “Music”]) = UNKNOWN if Person.hobbies = ?
(Person.hobbies) SUBSET OF ([“Tennis”, “Soccer”, ?]) = FALSE if Person.hobbies = “Tennis”, “Soccer”
('a', 'b', 'c') SUBSET OF (['a', 'b', 'c']) will result in an error.

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type	note

Values between single quotes are considered value list items. For backwards compatibility reasons, a comma separated sequence of value list items is treated as a collection. That's why there is no need to enclose the values between square brackets. In fact if you do add the square brackets you create a matrix rather than a list.

UNION

Adds two collections of the same base type to a new collection.

Syntax

Code Block
UNION ( collection1 , collection2 )

collection1 - First collection to be added to the new collection.
collection2 - Second collection to be added to the new collection.

Return type

collection

Examples

Suppose you have a Parent and a Child entity, where Parent has a multivalued relation with Child via the relation Parent.has_Children. With this model the following instances are created:

...

UNION ( Parent[Parent_1].has_Children , Parent[Parent_2].Has_Children ) results in a collection of all Child instances
UNION ( Parent[Parent_1].has_Children.name , Parent[Parent_2].Has_Children.name ) = “Kim”, “Rick”, “Bob”, “Mary”
if Child_2 is active, UNION ( Child.hobbies , “Reading” ) = “Tennis”, “Dancing”, “Reading”
UNION ( Child[Child_1].hobbies , Child[Child_2].hobbies ) = “Reading”, “Dancing”, “Tennis”

INTERSECTION

This function determines the intersection of two collections. It returns a collection containing the items that are present in both specified collections.

Syntax

Code Block
INTERSECTION ( collection1 , collection2 )

collection1, collection2 - Collections to be intersected. These collections must be of the same base type.

Return type

collection

Examples

Suppose the following model. Entity Teacher has a multivalued relation with entity Child via the relation Teacher.teaches_Children.

...

INTERSECTION ( Teacher[Teacher_1].teaches_Children , Teacher[Teacher_2].teaches_Children ) results in a collection of Child instances Child_1 and Child_3
INTERSECTION ( Teacher[Teacher_1].teaches_Children.name , Teacher[Teacher_2].teaches_Children.name ) = “Kim”, “Bob”
INTERSECTION ( Child[Child_1].hobbies , Child[Child_3].hobbies ) = “Reading”
INTERSECTION ( Child[Child_2].hobbies , Child[Child_3].hobbies ) results in an empty list

DIFFERENCE

...

a collection containing all the items from collection1 that are not present in

...

Syntax

Code Block
DIFFERENCE ( collection1 , collection2 )

...

collection2

...

.

...

Return type

collection

Examples

...

DIFFERENCE ( 1 , 1 ) results in an empty list

SYMMETRIC_DIFFERENCE

...

Determines the symmetric difference between two collections.

...

Returns a collection with the elements of the provided collections which are in either one of the collections, but not in both.

A note on collections and duplicates.

...

Syntax

Code Block
SYMMETRIC_DIFFERENCE ( collection1 , collection2 )

collection1, collection2 - Collections to be intersected. These collections must be of the same base type.

Return type

collection

Examples

SYMMETRIC_DIFFERENCE ( [ "a", "b", "c"] , [ "c", "d", "e" ] ) = [ "a", "b", "d", "e" ]
SYMMETRIC_DIFFERENCE ( [ "nv" , "bv" ] , [ "NV" ] ) = [ "bv" ]
SYMMETRIC_DIFFERENCE ( 1 , 1 ) results in an empty list

Functions

Include Page

	Collection function EXISTS
	Collection function EXISTS

Include Page

	Collection function EACH
	Collection function EACH

Include Page

	Collection function ALL
	Collection function ALL

Include Page

	Collection function COLLECT FROM WHERE
	Collection function COLLECT FROM WHERE

Include Page

	Collection function COLLECT FROM NAMED WHERE
	Collection function COLLECT FROM NAMED WHERE

Include Page

	Collection function UNPACK
	Collection function UNPACK

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	Collection function LIST
	Collection function LIST

Include Page

	Collection function SIZE
	Collection function SIZE

Include Page

	Collection function UNIQUE
	Collection function UNIQUE

Include Page

	Collection function SUBSET OF
	Collection function SUBSET OF

Include Page

	Collection function UNION
	Collection function UNION

Include Page

	Collection function INTERSECTION
	Collection function INTERSECTION

Include Page

	Collection function DIFFERENCE
	Collection function DIFFERENCE

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	Collection function SYMMETRIC_DIFFERENCE
	Collection function SYMMETRIC_DIFFERENCE

Include Page

	A note on collections and duplicates
	A note on collections and duplicates

Collections vs. lists

UNIQUE, SUBSET, UNION and INTERSECTION return a collection of data, i.e. double entries are removed. However, COLLECT statements, + and - return a list of data. You have to be aware of this when using the SIZE or UNPACK function.

Example

Statuses = ["a","b","c","d","a","b","c","d"].

Result

The expression "SIZE ( COLLECT Status FROM {Statuses} )" will result in 8. Note that duplicates are not removed.

The expression "SIZE ( UNIQUE ( COLLECT Status FROM {Statuses} ) )" will result in 4, as the unique filters the duplicates.

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type	warning

When the expression is completely evaluated, all duplicates are filtered as well. Using COLLECT Status FROM {Statuses} as a default expression on an attribute, will result in 4 elements.

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Key

Overview

SIZE

UNIQUE

SUBSET OF

UNION

INTERSECTION

DIFFERENCE

Functions

Collections vs. lists