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Learn more about the functions ISNULL, ISUNKNOWN, IFUNKNOWN, IS A, TYPE OF, ISACTIVE, GUID.
Overview
| Function | Description |
|---|---|
ISNULL | Checks whether a value is unknown. |
ISUNKNOWN | Replaces a value if that value is unknown. |
IFUNKNOWN | Alternative notation of the ISUNKNOWN function, which increases readability especially for long expressions. |
IS A | Checks the entity type of an instance. |
TYPE OF | Determines the entity type of an instance. |
ISACTIVE | Determines if an instance of a specific entity type is currently active. |
GUID | Generates a globally unique identifier which can later be used to uniquely mark and recognize a desired element. |
Functions
Checks whether a value is unknown. Syntax Return type Examples Suppose the following data model.
ISNULL
ISNULL ( expression )
Input
expression - Expression that is checked.boolean - TRUE of the attribute is unknown, FALSE otherwisePerson.name Person.SequenceNumber “Bob” 654 “Jane” ? Active Person Expression Result Type Bob ISNULL ( Person.SequenceNumber ) FALSE boolean Jane ISNULL ( Person.SequenceNumber ) TRUE boolean
Replaces a value if that value is unknown. Syntax Return type Examples Suppose the following data model. Both parameters of the
ISUNKNOWN
ISUNKNOWN ( expression , value )
Inputs
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.any type, equals the expression typePerson.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 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
Alternative notation of the ISUNKNOWN function, which increases readability especially for long expressions. This function replaces a value if that value is unknown. The IFUNKNOWN function takes precedence 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 Inputs 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. Both parameters of the
IFUNKNOWN
expression IFUNKNOWN value
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 IFUNKNOWN false false Boolean IFUNKNOWN function must be of the same datatype. If they differ in datatype, you get this validation error:Could not find function: IFUNKNOWN matching arguments System.Collections.ArrayList
Checks the entity type of an instance. The function returns TRUE if the selected instance is of the specified entity. Syntax Return type Examples Suppose a domain model in which there is a singleton entity If you want to determine the number of bedrooms is the residence: If you want to determine the number of bathrooms is the residence:
IS A
instance IS A entity_name
Inputs
instance - Instance to check.entity_name - Name of the entity as string.BooleanResidence that has a multivalued relation hasRooms with Room. Room is the base entity for singleton Kitchen and not singletons Bedroom and Bathroom.COUNT ( COLLECT Room FROM Residence.hasRooms WHERE ( Room IS A “Bedroom” ) )COUNT ( COLLECT Room FROM Residence.hasRooms WHERE ( Room IS A “Bathroom” ) )
Determines the entity type of an instance. The function returns the name of the entity. Syntax Input Return type Examples Suppose a domain model in which there is a singleton entity
TYPE OF
TYPE OF base_entity
base_entity - Name of the instance's base entity.stringResidence 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”
Determines if an instance of a specific entity type is currently active. Inputs Return type boolean - TRUE if one of the instances is active, FALSE otherwise Singletons are always active, so Examples Suppose the following data model.
ISACTIVE
ISACTIVE instances [WHERE condition]
ISACTIVE <singleton> will always return TRUE 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
Generates 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 Return type String - the generated GUID Examples
GUID
GUID()
Expression Result GUID() 4a18d6a7-03c1-47f9-b6aa-eae7d746050e GUID() 91d37298-23ec-4bd4-8523-9c7e7745cb9d
Overview
Content Tools
3 Comments
Ronald Peterson
What is the best use of the GUID function? Should I make an attribute userset with the result?
Unknown User (m.schadd)
Ronald Peterson Well that depends. The trueth maintenance mechanism will not create a new guid unless something else in the expression changes (e.g., system.currentPage + GUID(), which is discouraged). So as long as your session is alive, the guid stays the same. In case that you send the guid to an external service, the external service can store and use the guid. In case you want to store the guid value in an aggregate, then you might want to make it user-set. As only user-set values are stored in an aggregate, you would get a new guid when reading the aggregate. In case this is not desired, you should make the attribute user set first (using the Service call type: AQ_Instance_Update). This is similar to the consideration when using NOW or TODAY.
Pieter Lubbers
Can you confirm that the ISACTIVE function works the same as a reusable expression? That is: without context.
I tried the following function (in a repeat box on a container) without success:
COLLECT A FROM ALL A WHERE( ISACTIVE( B ) AND A.isTrue)
The error states: ALIAS must be specified for each/exists/isactive expressions when the from type is not of entity time.
I recall that the following reusable expression doesn't work with the same error:
{RE} = A.isTRUE
COLLECT A FROM ALL A WHERE( A.Number = COLLECT B FROM ALL B WHERE( {RE} AND B.Number = A.Number)
Or more simply:
{RE} = ISACTIVE(A) → Works
{RE} = ISACTIVE(A) AND TRUE → Error