You may want to make a copy of an item descriptor without doing any dynamic typing of that item descriptor. If so, you can use the copy-from attribute. This creates a copy of the specified item descriptor, to which you can add additional properties. This is a way to share property definitions between different item descriptors, or perhaps to add additional properties to an existing item descriptor definition. Because these item descriptors share the same tables (and thus the same data), it might be unwise to use both old and new item descriptors. Instead, it might be better to use the super-type attribute and sub-type-property attribute if you want to use both.