The topics included in an FTML map inherit the map's metadata. In the same way, child topics inherit metadata from their parent topics. If a topic inherits metadata that it already had, the topic takes on both values (its own and the inherited one).
In all cases, metadata keys beginning with the prefix ft: is not inherited. This includes the following metadata keys:
ft:titleft:localeft:baseIdft:clusterIdft:openModeft:originUrlft:editorialTypeft:lastEditionft:descriptionft:prettyUrl
Example
A topic has the metadata product=foo and inherits the metadata product=bar from the document. As a result, its new metadata is product=foo,bar.