 They can be used to represent tables, for example, where each table is given a particular EntityClass near the front of the Item, and each column is given a different Attribute.The Items of the table each start with a particular EntityClass, then therehe are one or more normal primitives representing an 'entity' (like a key) then there is a particular Attribute corresponding to a column, and finally some normal primitives representing the value of that Attribute.This simple pattern can be extended at any time to allow nested tables inside any Attribute, or nested Attributes inside other Attributes, or multi-valued Attributes and much more.