mw98gt

I am just finishing CH 13 of the book, on XML, and I am a little confused with the schemas. How come I am allowed to open an XML file if it doesn't adhere to its schema? It seems all a web browser cares about is properly formatted XML regardless of what elements the schema calls for. My research points to php functions that validate the xml based on a scheme, which is great, but why wouldn't the schema be read on its own when opening a raw XML file? It seems like the browser doesn't even care if the external schema file exists so why even reference it in the XML? In order to validate it I came up with tis code... $xml = new DOMDocument(); $xml -> load('books4.xml'); if (!$xml->schemaValidate('collection.xsd')) { echo "invalid<p/>"; } else { echo "validated<p/>"; } I had to separately point to the schema in this code, it could not even "read" the linked schema in the XML so again why put it in the XML? Or would an expansion of the SimpleXML parser have an ability to extract that info and validate the XML against the XSD? Any clarification would be greatly appreciated!