metadata mapping file is domain specific. It allows individual domain to customize their domain environment, such as the display of their metadata field, the name of their public library, help url, etc. The metadata mapping currently is a xml file. It needs to be loaded into thalia via the resttest.jsp interface:

• write your domain metadata mapping using a text editor. See as an example.
• goto https://domainname.thalia.mit.edu/resttest.jsp and scrool down to meta data mapping. Copy and paste the mapping xml into the mapping text box, then click on "save mapping" button 

We are working on an UI interface to make this process easier.