48
DTD: Regular Expressions
<!ELEMENT name  
                     (firstName, lastName))
<name>
    <firstName>  . . . . . </firstName>
    <lastName>  . . . . . </lastName>
</name>
<!ELEMENT name  (firstName?, lastName))
DTD
XML
<!ELEMENT person   (name, phone*))
sequence
optional
<!ELEMENT person   (name, (phone|email)))
Kleene star
alternation
<person>
    <name>  . . . . . </name>
    <phone>  . . . . . </phone>
    <phone>  . . . . . </phone>
    <phone>  . . . . . </phone>
    . . . . . .
</person>