Self-closing tags in XML files

by

See the W3C specs for XML and XHTML:

It depends on the Element Type declaration

An element with no content is said to be empty. The representation of an empty element is either a start-tag immediately followed by an end-tag, or an empty-element tag.

but also

Empty-element tags may be used for any element which has no content, whether or not it is declared using the keyword EMPTY. For interoperability, the empty-element tag SHOULD be used, and SHOULD only be used, for elements which are declared EMPTY.

This means, when your DTD contains something like

<!ELEMENT img EMPTY>

you should use

<img/>

unless you have good reason to use

<img></img>

Note that SHOULD is defined in RFC2119 as

This word, or the adjective “RECOMMENDED”, mean that there
may exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood and
carefully weighed before choosing a different course.

If you are working with XML that does not have a DTD or Schema, you can also influence how the XML is serialized with a predefined libxml constant:

LIBXML_NOEMPTYTAG (integer): Expand empty tags (e.g. <br/> to <br></br>)

But note that this option is currently just available in the functions DOMDocument::save and DOMDocument::saveXML, so you cannot use it with SimpleXml.

More Related Contents:

  1. What characters do I need to escape in XML documents?
  2. How to generate sample XML documents from their DTD or XSD?
  3. XPath query to get nth instance of an element
  4. Can Chrome be made to perform an XSL transform on a local file?
  5. POST XML file using cURL command line
  6. Opening JSF Facelets page shows “This XML file does not appear to have any style information associated with it.”
  7. SVG rounded corner
  8. XSD – how to allow elements in any order any number of times?
  9. Represent space and tab in XML tag?
  10. In XML, is order important?
  11. If double slash (//) is used 2 times in XPath, what does it mean?
  12. How to unescape XML characters with help of XSLT?
  13. Replace dynamic content in XML file
  14. XSL xsl:template match=”/”
  15. Why PowerShell workflow is significantly slower than non-workflow script for XML file analysis
  16. distinct in Xpath?
  17. How can I select an element with multiple classes with Xpath?
  18. How to webscrape secured pages in R (https links) (using readHTMLTable from XML package)?
  19. WiX Installer: using xslt with heat.exe to update attributes
  20. Convert image (jpg) to base64 in Excel VBA?
  21. Unable to install R package in Ubuntu 11.04 [closed]
  22. Ruby XML to JSON Converter?
  23. Can a XML element contain text and child elements at the same time?
  24. How do I use PowerShell to Validate XML files against an XSD?
  25. Using CDATA inside another CDATA
  26. Including an XML file in an XML/XSL file
  27. How to sort XML in LINQ C# by an attribute value? Also MVC
  28. get the namespaces from xml with python ElementTree
  29. targetNamespace and xmlns without prefix, what is the difference?
  30. IIS7 URL Rewrite – Add “www” prefix

Leave a Comment