Tag Syntax
Superficially, XML tags look like HTML tags. Start-tags begin with
< and end-tags begin with
</. Both of these are followed
by the name of the element and are closed by >. However, unlike HTML tags, you are
allowed to make up new XML tags as you go along. To describe a
person, use <person> and
</person> tags. To describe
a calendar, use <calendar>
and </calendar> tags. The
names of the tags generally reflect the type of content inside the
element, not how that content will be formatted.
Empty elements
There’s also a special syntax for empty elements,
elements that have no content. Such an element can be represented
by a single empty-element tag that begins
with < but ends with
/>. For instance, in
XHTML, an XMLized reformulation of standard HTML,
the line-break and horizontal-rule elements are written as
<br /> and <hr /> instead of <br> and <hr>. These are exactly equivalent
to <br></br> and
<hr></hr>, however.
Which form you use for empty elements is completely up to you.
However, what you cannot do in XML and XHTML (unlike HTML) is use
only the start-tag—for instance <br> or <hr>—without using the matching
end-tag. That would be a well-formedness error.
Case-sensitivity
XML, unlike HTML, is case-sensitive. <Person> is not the same as
<PERSON> or <person>. If you open an element
with a <person> tag, you
can’t close it with a </PERSON> tag. You’re free to use
upper- or lowercase or both as you choose. You just have to be
consistent within any one element.
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