II.10 The Long Work-Area-2 Option

From time to time, GSS adds new output fields to a function’s WA2. For example, in 2011, the WA2s of several functions were enhanced to include fields for the 2010 census tract and block. In general, when new output fields are added to a Geosupport work area, GSS utilizes existing filler space in the work area for those fields, if available. In that way, the basic layout of the work area remains the same, and existing users of that function who do not need to make use of the new items are not compelled to modify their applications.

If there is not enough filler space available in a function’s WA2 to accommodate new fields, GSS introduces a ‘long WA2 option’ for that function, as described below. This approach enables new data items to be made available to applications that need them, without affecting existing applications that do not need them. The MSW functions that currently have the long WA2 option are Functions 1, 1E, 1A, BL and 3. The COW functions that currently have the long WA2 option are functions 1A and BL. The long WA2 option may be implemented for other functions in the future.

When issuing a two‑work‑area call to a function that has the long WA2 option, the application has the option to use either the ‘regular WA2’ (the work area layout that had already been in existence before the long WA2 option was introduced for that function), or the ‘long WA2’.  The application informs Geosupport that the long WA2 is being used by inserting an ‘L’ in a WA1 input field called the Long Work Area 2 Flag. When the long WA2 option is specified, it is the application’s responsibility to pass a WA2 of the proper length to the Geosupport driver.  If the application passes a blank in the Long WA2 Flag, the regular WA2 is used. Both the regular and long WA2s are documented in Appendix 2.

The MSW Function 3 exemplifies the role of the long WA2 option. MSW Function 3’s regular WA2 is 200 bytes long, almost all of which was long ago allocated to specific fields, leaving little filler space available for new fields. At some point in the past, the necessity to add new fields for which no space was available in Function 3's regular WA2 impelled the introduction of the long WA2 option for Function 3. Function 3’s long WA2 is 300 bytes long, and consists of the same 200 bytes of information that are returned in the regular WA2, followed by 100 additional bytes containing fields for several additional items that the regular WA2 was not designed to include, as well as ample filler space for future enhancements. Applications that existed prior to the introduction of the long WA2 option for Function 3, and that have no need of any of the fields returned in the last 100 bytes of the long WA2, are able to continue running properly without modification using the regular WA2.