A recent conversation with Rob Lefferts, Microsoft GM of Office Extensibility (I bet some think he is in charge of extending office space) moved me to think just how extensible the overall Office suite is right now.
In this context, Office is the complete collection of the desktop applications (Word, Excel, etc.), the servers (Exchange, SharePoint, etc.), and includes new offerings such as Sway. As such, it’s a pretty broad canvas for which Microsoft has to provide the necessary APIs and tool sets to allow developers to work their magic.