Hello,
depending on what exactly you are looking for, the following might help you.
a) If you are looking for a way to trigger metadata extraction, look for the Repository action "extract-metadata" that you can configure in a rule. This is implemented by ContentMetadataExtracter and may also be triggered by custom code.
b) If you are looking for supporting a metadata extraction for a specific type of content, look at implementing the interface MetadataExtracter (via base class AbstractMappingMetadataExtracter) where you can define how data should be extracted.
c) If you are looking for customizing the metadata extraction / metadata mapping for an already supported type of content, look at overriding the properties files in /tomcat/webapps/alfresco/WEB-INF/classes/alfresco/metadata/ which define the mapping for all out-of-the-box metadata extracters. Depending on the type of extracter, it may support far more data than is listed by default - unfortunately, the only reliable way to find out what they support is by looking at the corresponding source files.
Regards
Axel
