Contains elements that define a master for the document. A master is a shape on a stencil that you use repeatedly to create drawings. When you drag a shape from a stencil onto the drawing page, the shape becomes an instance of that master, and a local copy of the master is included in the document.
The MatchByName attribute determines how Microsoft Visio decides if a document master is already present when an instance of a master is dropped on the drawing page. It allows changes made to a document master to apply to new instances of the master, even if the instances are dragged from a stand-alone stencil file.