It is possible to specify if properties in the repository will be set if the extracted values are not null or if the properties already have a value. By default, PRAGMATIC is used. Generally you will not need to change this. Other values (CAUTIOUS, EAGER, PRUDENT) are described in OverwritePolicy. To use a different policy add a sys:overwritePolicy value to the Map returned from the extractMetadata method of the class extending AbstractMetadataExtractor (described above).
The following table shows which conditions must be met for overwriting the value: