Every municipality has a protocol established to maintain its tax maps and the GIS should exploit this protocol to reduce demand on human resources and, most importantly, error (Rehmann 1999, 2). A simple method is to treat the update like a puzzle. The goal of puzzle protocol is to make updates on hardcopy map sheets and use the separate sheets to piece together the final seamless dataset. Protocol is based on a situation where the GIS dataset is broken up in pieces to reflect the number of map sheets. Thus if there were 100 tax map sheets, there would be 100 separate corresponding digital components. Users, however, will work with one seamless copy. For the purposes of updating, a backup dataset is made for compartmentalizing into "puzzle pieces." At a predetermined interval, the overall parcel dataset would be modified by substituting all of the updated GIS pieces for the older, out-of-date dataset (Rehmann 1999, 2).
Attribute data tends to change more rapidly than parcel boundaries. Therefore, methods should be instituted to maintain attribute records that are used routinely in conjunction with the parcel dataset. Users should have a standard protocol for disengaging and reestablishing the links between attribute databases and the spatial dataset. For a GIS enterprise of any size, this protocol may be more difficult to institute than updating parcel boundaries. The challenge is that multiple departments may be responsible for maintaining specific attribute databases without a clear understanding of the database's relevancy to the GIS.
Individual departments tend to have their own time schedules for updating information based on staffing resources and project demands. Often data entry is last on the list of priorities. While these updates may be performed independently of one another, a coordinated effort is required to make all users aware of the currency of the data. A GIS enterprise may find it necessary to create a "Date Of Last Transaction" field in its attribute databases (Rehmann 1999, 2). The data in this "Date Of Last Transaction" field could be used to delete old records or allow the GIS to distinguish between current and outdated records when performing operations.
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