I want to make a NULL XML file. I have come up with the following:

<?xml version="1.0" encoding="UTF-8"?>
<open>
</open>

Is this considered a NULL XML file? Or is it just an empty file with .xml extension.

CodePudding user response：

Short answer: A "NULL XML file" is neither conventional nor standard terminology but likely refers to a minimal XML document, a single empty element, in a file.

Longer explanation: Your example XML has

1. an XML declaration,
2. an open element,
3. a text node child of the open element consisting of a newline character.

An XML document, which is standard terminology, must have at least a document element – an empty file is not a well-formed XML document.

An XML parsed entity, which also is standard terminology, may minimally be an empty file.

So:

• A file consisting of an empty element, <e/>, is a minimal XML document.

• An empty file is a minimal XML parsed entity.

Given that user-level tools and conversations regarding "XML files" most frequently are about files containing XML documents, someone asking for a "NULL XML file" likely wants a file containing a minimal XML document: <e/>.

_{Thanks to Michael Kay for the helpful suggestion to consider XML parsed entities in addition to XML documents.}