Miscellaneous function: ISNULL

ISNULL

This function checks whether a value is unknown

Syntax

ISNULL ( expression )

expression - Expression that is checked.

Return type

boolean - TRUE of the attribute is unknown, FALSE otherwise

Examples

Suppose the following data model.

Person.name	Person.SequenceNumber
“Bob”	654
“Jane”	?

Active Person	Expression	Result	Type
Bob	ISNULL ( Person.SequenceNumber )	FALSE	Boolean
Jane	ISNULL ( Person.SequenceNumber )	TRUE	Boolean

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ISUNKNOWN

This function replaces a value if that value is unknown.

Syntax

ISUNKNOWN ( expression , value )

expression- Expression of which the value has to be returned if that value is known.
value - Value to return if the expression value is unknown.

Return type

any type, equals the expression type

Examples

Suppose the following data model.

Person.name	Person.SequenceNumber
“Bob”	654
“Jane”	?
“Mary”	667
“Rick”	?
“Ron”	?
“Jenny”	765
?	111

Active Person	Expression	Result	Type
Jane - ?	ISUNKNOWN ( Person.SequenceNumber , 999 )	999	Integer
Mary - 667	ISUNKNOWN ( Person.SequenceNumber , 999 )	667	Integer
? - 111	ISUNKNOWN ( Person.Name , "customer" )	"customer"	String

Both parameters of the ISUNKNOWN function must be of the same datatype. If they differ in datatype, you get this validation error in studio:

Could not find function: ISUNKNOWN matching arguments System.Collections.ArrayList

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IFUNKNOWN

An alternative notation of the ISUNKOWN function, which increases readability especially for long expressions. This function replaces a value if that value is unknown.

The IFUNKNOWN function takes precendence over any other binary operator (except for the "NOT" operator).
For example, this means that the expression A.B AND C.D IFUNKNOWN FALSE will be interpreted as A.B AND (C.D IFUNKNOWN FALSE). You can use parentheses to influence this behavior, e.g. by writing (A.B AND C.D) IFUNKNOWN FALSE.
For the "NOT" operator the following expression "X AND NOT B IFUNKNOWN FALSE", can also be read as "X AND ((NOT B) IFUNKNOWN FALSE)"

Syntax

expression IFUNKNOWN value

expression- Expression of which the value has to be returned if that value is known.
value - Value to return if the expression value is unknown.

Return type

any type, equals the expression type

Examples

Suppose the following data model.

Person.name	Person.SequenceNumber	Person.HasDrivingLicense
“Bob”	654	true
“Jane”	?	true
“Mary”	667	false
“Rick”	?	?
“Ron”	?	false
“Jenny”	765	true
?	111	true

Active Person	Expression	Result	Type
Jane - ? - true	Person.SequenceNumber IFUNKNOWN 999	999	Integer
Mary - 667 - false	Person.SequenceNumber IFUNKNOWN 999	667	Integer
? - 111 - true	Person.Name IFUNKNOWN "customer"	"customer"	String
"Rick" - ? - ?	NOT Person.HasDrivingLicense IFUNKOWN false	false	Boolean

Both parameters of the IFUNKNOWN function must be of the same datatype. If they differ in datatype, you get this validation error in studio:

Could not find function: IFUNKNOWN matching arguments System.Collections.ArrayList

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IS A

Use this function to check the type of an instance. The function returns TRUE if the selected instance is of the specified entity.

Syntax

instance IS A entity_name

instance - Instance to check.
entity_name - Name of the entity as string.

Return type

boolean

Examples

Suppose a domain model in which there is a singleton entity Residence that has a multivalued relation hasRooms with Room. Room is the base entity for singleton Kitchen and not singletons Bedroom and Bathroom.

If you want to determine the number of bedrooms is the residence:

COUNT ( COLLECT Room FROM Residence.hasRooms WHERE ( Room IS A “Bedroom” ) )

If you want to determine the number of bathrooms is the residence:

COUNT ( COLLECT Room FROM Residence.hasRooms WHERE ( Room IS A “Bathroom” ) )

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TYPE OF

Use this function to determine the type of an instance. The function returns the name of the entity.

Syntax

TYPE OF base_entity

base_entity - Name of the instance's base entity.

Return type

string

Examples

Suppose a domain model in which there is a singleton entity Residence that has a multivalued relation hasRooms with Room. Room is the base entity for singleton Kitchen and not singletons Bedroom and Bathroom.

for the Kitchen instance the expression ( TYPE OF Room ) = “Kitchen”
for the Bedroom instances the expression ( TYPE OF Room ) = “Bedroom”

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ISACTIVE

Use this function to determine if an instance of a specific type is currently active.

ISACTIVE instances [WHERE condition]

instances - instances to search
condition - optional condition to limit the collection of instances to check

Return type

boolean - TRUE if one of the instances is active, FALSE otherwise

Singletons are always active, so ISACTIVE <singleton> will always return TRUE

Examples

Suppose the following data model.

instance_id	Person.name	Person.Age
Person_1	“Bob”	14
Person_2	“Jane”	25
Person_3	“Mary”	30

Active Person	Expression	Result	Type	Note
None	ISACTIVE Person	FALSE	Boolean
Person_1	ISACTIVE Person	TRUE	Boolean
Person_1	ISACTIVE Person WHERE Person.Age >= 18	FALSE	Boolean
None	ISACTIVE system	TRUE	Boolean
None	Person.Age >= 18	Error		No Person is active
None	( ISACTIVE Person ) AND Person.Age >= 18	FALSE	Boolean	The expression is evaluated left-to-right and fails on ( ISACTIVE Person ) instead of giving an error

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GUID

This function is able to generate a globally unique identifier which can later be used to uniquely mark and recognize a desired element.

The GUIDs are represented as 32 hexadecimal digits, displayed in five groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters.

Syntax

GUID()

Return type

String - the generated GUID

Examples

Expression	Result
GUID()	4a18d6a7-03c1-47f9-b6aa-eae7d746050e
GUID()	91d37298-23ec-4bd4-8523-9c7e7745cb9d

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ISNULL

ISUNKNOWN

IFUNKNOWN

IS A

TYPE OF

ISACTIVE

GUID