You may specify that a listof property is designated as one which can reference external documents. The command causes buttons to be presented at the bottom of the listof property: an Open button, a Browse Externally button, and a Browse Internally button. You may use these buttons to browse and select external documents, or type in external hyperlinks, or browse the internal Files table of the encyclopedia’s database, or open an external or internally referenced document.

System Architect enforces the following restrictions on URLS property: It may not be Key.