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SIZE

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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:

 

Parent instance	Child instance	Child.name	Child.hobbies
Parent_1	Child_1	“Kim”	“Reading”, “Dancing”
Parent_1	Child_2	“Rick”	“Tennis”, “Dancing”
Parent_1	Child_3	“Bob”	“Painting”, “Basketball”, “Reading”
Parent_2	Child_4	“Mary”	“Football”

 

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

 

UI Text Box
type note
COUNT and SIZE are similar except for UNKNOWN: COUNT ( ? ) = UNKNOWN

 

UNIQUE

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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.

 

Person instance	Person.name
Person_1	“Kim”
Person_2	“Rick”
Person_3	“Bob”
Person_4	“Rick”

 

• 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)

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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.

 

Teacher instance	Child instance	Child.name	Child.hobbies
Teacher_1	Child_1	“Kim”	“Reading”, “Dancing”
Teacher_1	Child_2	“Rick”	“Tennis”, “Dancing”
Teacher_1	Child_3	“Bob”	“Painting”, “Basketball”, “Reading”
Teacher_2	Child_1	“Kim”	“Reading”, “Dancing”
Teacher_2	Child_3	“Bob”	“Painting”, “Basketball”, “Reading”
Teacher_2	Child_4	“Mary”	“Football”

 

• 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

This function returns a collection containing all the items from collection1 that are not present in collection 2.

Syntax

Code Block
DIFFERENCE ( collection1 , collection2 )

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

Return type

• collection

Examples

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

SYMMETRIC_DIFFERENCE

This function determines the symmetric difference between two collections. It returns a collection with the elements of the provided collections which are in either one of the collections, but not in both.

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

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.