Page History
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 |
Table of Contents minLevel 2
...
bgColor | white |
---|
ISNULL
This function checks whether a value is unknown
Syntax
Code Block |
---|
ISNULL ( expression ) |
- expression - Expression that is checked.
Return type
- boolean - TRUE of the attribute is unknown, FALSE otherwise
Examples
Suppose the following data model.
...
bgColor | white |
---|
ISUNKNOWN
This function replaces a value if that value is unknown.
Syntax
Code Block |
---|
ISUNKNOWN ( expression , value ) |
- expression- Expression of which the value has to be returned if that value is known.
- value - Value to return if the attribute value is unknown.
Return type
- any type, equals the attribute type
Examples
Suppose the following data model.
...
UI Text Box | ||
---|---|---|
| ||
Both parameters of the
|
...
bgColor | white |
---|
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
Code Block |
---|
expression IFUNKNOWN value |
expression- Expression of which the value has to be returned if that value is known.
value - Value to return if the attribute value is unknown.
Return type
any type, equals the attribute type
Examples
Suppose the following data model.
...
UI Text Box | ||
---|---|---|
| ||
Both parameters of the
|
...
bgColor | white |
---|
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
Code Block |
---|
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” ) )
...
bgColor | white |
---|
TYPE OF
Use this function to determine the type of an instance. The function returns the name of the entity.
Syntax
Code Block |
---|
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”
...
bgColor | white |
---|
ISACTIVE
Use this function to determine if an instance of a specific type is currently active.
Code Block |
---|
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
UI Text Box type note Singletons are always active, so
ISACTIVE
<singleton> will always returnTRUE
Examples
Suppose the following data model.
...
bgColor | white |
---|
GUID
...
a globally unique identifier which can later be used to uniquely mark and recognize a desired element. |
...
Functions
Include Page Miscellaneous function ISNULL Miscellaneous function ISNULL
Include Page Miscellaneous function ISUNKNOWN Miscellaneous function ISUNKNOWN
Include Page Miscellaneous function IFUNKNOWN Miscellaneous function IFUNKNOWN
Include Page Miscellaneous function IS A Miscellaneous function IS A
Include Page Miscellaneous function TYPE OF Miscellaneous function TYPE OF
Include Page Miscellaneous function ISACTIVE Miscellaneous function ISACTIVE
Include Page Miscellaneous function GUID Miscellaneous function GUID
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
Code Block |
---|
GUID() |
Return type
String - the generated GUID
Examples
...