Systems and methods are provided for receiving, at a computing system, an expression in a formula language to generate a user interface to be displayed, where the expression includes data to be retrieved. The computing system may determine whether a first portion of the data for the expression has been retrieved from at least one data source when the user interface is to be generated based on a signal received by the computing system from the at least one data source. When the first portion of the data is available, the user interface may be output. When the signal is received by the computing system that the first portion of the data for the expression is not available, the computing system outputs the user interface without the first portion of the data and revises the user interface to include the first portion of the data when the first portion of data becomes available.