XML documents should have an XML declaration on the first line,
although this is not strictly needed
<?xml version="1.0" encoding="US-ASCII" standalone="yes"?>
<person>
<personal_name>Tom</personal_name>
<family_name>Gedeon</family_name>
<phone_number>51052</phone_number>
</person>
XML documents should be well formed (conform to XML syntax rules):
- Start tags matching end tags,
- Elements not overlapping,
- Tags are case sensitive
(<p> is different from <P>!)
- XML documents must have a root element, and
- XML attribute values must always be quoted
XML documents should be valid (conform to some
semantic
rules).