Shredding

The previous discussion concentrated primarily on the composition from relational data to XML data. In the case of shredded XML, we must first solve the opposite problem: How do we take XML data and represent it in a relational database? Stated another way, How do we encode an XML document as a set of relational entities, relations, and attributes?

The issues involved for shredding are very similar to the issues for update for any composed mapping technique, which is not surprising, given that shredding an XML document is essentially an update operation that adds a new instance of the document to the store. Thus it is also not surprising that the same basic approaches that work for composed mapping techniques work for shredding as well—so long as they preserve the ability to update. In this section we explore a few additional issues that are unique to shredding.