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. e e Iltl"i'-",) UVU....:l!.4 Functional Specification for the Planning Model The general user interface design objectives will be to provide a reasonable level of error checking, without restricting the user's freedom, to detect errors as early as possible and to provide understandable error messages in plain English whenever errors are detected. l Documenting or "Commenting" Scenarios It is important for users to be able to save the work they have invested in specifying a scenario, to reuse a scenario at a later time and to share it with other users. This implies that a user must be able to build up a library of scenarios over time and determine which is the appropriate one for a particular purpose. Accordingly, users need to be able to give names to scenarios and to append comments to scenarios explaining in prose what the scenarios assume or address. Difference Files The functional requirement that users be able to save and exchange scenarios implies the ability to capture the differences between any scenario and the Baseline. This ability has been referred to as an abstract entity called a "difference file. " The primary use of the difference file is to enable efficient storage of the specification of a scenario and to enable it to be regenerated automatically by other users wishing to verify scenario results. A secondary use of the difference file will be to provide a human-readable form of documentation of the components of a scenario's definition. A related functional requirement for the user interface is to provide feedback to the user during the process of specifying a scenario. The user should be able to display a list the specifications included in the new scenario up to that point, in order to have confirmation of the work already completed. Support for Running the Model and Generating Output Before a model run is initiated, there are two categories of instructions or specifications which the user will be able to give, which are conceptually distinct from the set of assumptions which define a scenario. The first comprises the specification of time-dependent data and initial conditions to be used in the model run. The second comprises the specification of the output to be generated by the model run. It remains to be determined whether either or both of these specifications should be incorporated into the definition of a named "scenario" for purposes of the difference file, or whether these specifications should be saved separately in a manner which would allow their convenient application to different "scenarios." Time Interval Specification The Baseline will include time-series data for inflows, runoff forecasts and agricultural demands, all of which reflect historical climatological and hydrologic conditions for a 39-year period of record. It is important to understand that all three types of data reflect the occurrence of the same "dry" and "wet" years, so that the substitution of alternative data sets for only one or another class of data would represent a mixture of hypothetical and historical conditions. It is planned to provide support to users in selecting any whole-year sub-interval within the 39-year period of record. Model years will correspond to "water years," I.e. October through September. Initial conditions of reservoir storage and groundwater return flows in- transit are also logically required as part of the specification of a time interval. By default, the initial values for these parameters for any year will be the values generated in the Baseline run for the end of the preceding year. Users will be able optionally to specify alternative reservoir 21 ,."^ ,-u..,~,_.. 4" ;-!L;,,;.,-~1