There are a few more restrictions on XML than on HTML; they make parsing of XML simpler.
Unlike HTML, XML does not allow you to omit tags. This guarantees that parsers know where elements end.
The following example is acceptable HTML, but not XML:
<table> <tr> <td>Dog</td> <td>Cat <td>Mouse </table>
To change this into well-formed XML, you need to add all the missing end tags:
<table> <tr> <td>Dog</td> <td>Cat</td> <td>Mouse</td> </tr> </table>
Empty elements cannot be represented in XML in the same way they are in HTML. An empty element is one that is not used to mark up data, so in HTML, there is no end tag. There are two ways to handle empty elements:
Place a dummy tag immediately after the start tag. For example:
<img href="picture.jpg"></img>
Use a slash character at the end of the initial tag:
<img href="picture.jpg"/>
This tells a parser that the element consists only of one tag.
XML is case-sensitive, which allows it to be used with non-Latin
alphabets. You must ensure that letter case matches in start and
end tags: <MyTag> and </Mytag> belong
to two different elements.
White space within tags in XML is unchanged by parsers.
All XML elements must be properly nested. All child elements must be closed before their parent elements close.
