Representing Null vs. EmptyString in XML

[James (archive)]

In certain applications, it is necessary to distinguish between an emptyString vs. a null value. What is the appropriate way to make this distinction in XML?

<elementName></elementName>
looks like a zero-length string (emptyString) but will evaluate to null.

The data element in question may have its own datatype (string, title, name, etc.) but also need to hold an emptyString value.

 

[Richard Tobin]

In certain applications, it is necessary to distinguish between an emptyString vs. a null value. What is the appropriate way to make this distinction in XML?

There isn't a way to do this defined in plain XML, but you can make up your own way of doing it. A natural way is to use an attribute, and if you're using XML Schema then it provides one: xsi:nil="true" (where xsi is bound to the schema instance namespace). Nothing stops you from using this even when you're not using XML Schema, though you will have to interpret it yourself in the application.

-- Richard