It states that a program should not continue to process an XML document if it finds an 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.

For validating XML files xmlvalid is a command-line utility."xmlvalid" ElCel Technology is produced and maintained. .

Against a DTD xmlvalid validates the XML contents For each URL. The DTD is determined by the DOCTYPE declaration within the XML file or may be specified explicitly by using the --dtd option. Against an XML schema xmlvalid does not perform any validation .

Each filename passed on the command line is treated as a URL. If no protocol is present in the URL, it is assumed to refer to a local file. For example 'c:\test.xml' is treated as being equivalent to the URL 'file:///c:\test.xml'. To read from the standard input specify a URL of '-'.

Via a proxy server xmlvalid can be configured to route HTTP network.

On Microsoft Windows platforms, to compensate for the lack of shell file name expansion, xmlvalid automatically expands file names containing wild-card characters ('*' and '?') into a list of matching files. This expansion only occurs when the URL(s) look like file names, i.e. they do not contain a protocol such as "file:".

The xmlvalid message can be translated into your native language.