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5.1. Avalible expression elements
#
This operator indicates usage of field name, ex. "#userName"
static text
Static text in expression, ex. 'hello'
+
This operator concats two subexpressions, ex. "#userName + '(' + #userLogin + ')'"
[ and ]
use it when you want to get one of fields of corresponding entity (see ModelDefinitionOverview-belongsTo), ex. "#product['name']"