The SQL repository query system lets you create a query against a parent item descriptor that returns items of a child item descriptor. For example, a repository might define the following item descriptors and properties:

Given these inheritance relationships, you can create the following queries against items of type products, although products does not contain the queried properties — waterproofRating, size, and channelCount:

products whose waterproofRating is 'JIS-4'
products whose channelCount = 7
products whose waterproofRating is 'JIS-4' OR whose size > 7