Companion

The property the element declares stands where the modifier found it, and what something else works out from that write is left where it is.

Every property the element's write landed on stands where the modifier found it: the one the element declares, and every other its setter writes with it. The default.

The element undertakes nothing about the property: it installs content the next content replaces, it leaves the property to a derivation that answers afresh as it goes, or it writes onto a collaborator the component may have replaced since.