5. The computer readable storage medium of claim 2 , further comprising executable instructions to create a placeholder for an offset and a placeholder for a date constant or a date variable for each time period added by the user in the workspace.
2. The computer readable storage medium of claim 1 , wherein the expression components are selected from the list comprising: data model objects; aggregations; functions; operators; Boolean operators; time periods; integer constants; floating point constants; string constants; Boolean constants; and date constants.