The W3C XML specification states that a program should not continue to process an XML document if it finds a validation error. The reason is that XML software should be easy to write, and that all XML documents should be compatible. With HTML it was possible to create documents with lots of errors (like when you forget an end tag). One of the main reasons that HTML browsers are so big and incompatible, is that they have their own ways to figure out what a document should look like when they encounter an HTML error. With XML this should not be possible.
However, when creating an XML document, errors are very easily introduced. When working with large projects or many files, the probability that errors will occur is even greater. Determining that your project is error free can be time consuming and even frustrating. For this reason <oXygen/> provides functions that enable easy error identification and rapid error location.
XML with correct syntax is Well Formed XML.
A Well Formed XML document is a document that conforms to the XML syntax rules.
All XML elements must have a closing tag.
XML tags are case sensitive.
All XML elements must be properly nested.
All XML documents must have a root element.
Attribute values must always be quoted.
With XML, white space is preserved.
If you select menu Ctrl+Shift+W) or click the toolbar button <oXygen/> checks your current document for any deviation from these rules. If any error is found the result is returned to the Message Panel. Each error is one record in the Result List and is accompanied by an error message. Clicking the record will open the document containing the error and highlight the approximate location.
+ -> (Example 4.1. Check XML Form Error Message
In our example we will use the case where an end tag is missing from a Docbook listitem element. In this case running Check XML Form will return the following error.
F The element type "listitem" must be terminated by the matching end-tag "</listitem>".
To resolve the error, click in the result list record which will locate and highlight the errors approximate position. Review the "listitem" elements, identify which is missing an end tag and insert </listitem>.
Also the files contained in the current project and selected with the mouse in the Project view can be checked for well-formedness with one action available on the popup menu of the Project view :