Using XML with Legacy Business Applications

Nillable Elements

Schema language offers a feature that allows you to identify an Element as being nillable, that is, capable of representing a null value. This is the same as saying that a column in a table in a relational database can be null. With this feature you can create an instance document with an Element that is empty but that has an attribute of xsi:nill with a boolean value of true. Strictly speaking, as far as the schema language syntax goes this is not the same as saying that the Element is empty or that it is absent. However, what your application chooses to do with such Elements is probably up to you. I've not seen this feature used yet. However, I will be surprised if I don't find some clever monkey using it before I retire from ...