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Perhaps the primary function in the data storage and retrieval subsystem involves the editing and updating of data. Frequently, the following data editing capabilities are required:

interactive editing of spatial data;
interactive editing of attribute data;
the ability to add, manipulate, modify, and delete both spatial features and attributes (independently or simultaneously) ; and the
ability to edit selected features in a batch processing mode.

Updating involves more than the simple editing of features. Updating implies the resurvey and processing of new information. The updating function is of great importance during any GIS project. The life span of most digital data can range anywhere from 1 to 10 years. Commonly, digital data is valid for 5 to 10 years. The lengthy time span is due to the intensive task of data capture and input. However, often periodic data updates are required. These frequently involve an increased accuracy and/or detail of the data layer. Changes in classification standards and procedures may necessitate such updates. Updates to a forest cover data layer to reflect changes from a forest fire burn or a harvest cut are typical examples.

Many times data updates are required based on the results of a derived GIS product. The generation of a derived product may identify blatant errors or inappropriate classes for a particular layer. When this occurs updating of the data is required. In this situation the GIS operator usually has some previous experience or knowledge of the study area.

Commonly the data update process is a result of a physical change in the geographic landscape. Forest fires are a prime example. With this type of update new features are usually required for the data layer, e.g. burn polygons. As well, existing features are altered, e.g. forest stands that were affected. There is a strong requirement for a historical record keeping capability with this type of update process. Users should be aware of this requirement and design their database organization to accommodate such needs. Depending on the particular GIS, the update process may involve some data manipulation and analysis functions.