A method displays a user interface (UI) that includes a flow diagram having a plurality of nodes, receives user specification of a validation rule for a first node of the plurality of nodes in the flow diagram, and determines that an intermediate data set violates the validation rule. In response to determining that the first intermediate data set violates the validation rule, the method identifies errors corresponding to rows in the intermediate data set, and displays an error resolution UI that provides information about the errors. The error resolution UI includes a data flow trace region providing lineage of the errors in the flow. When a user selects an error in the data flow trace region, the data flow trace region is updated to provide the lineage of the selected error, including an updated graphic depiction for the respective error at each visually represented node.