Chapter 25, Problem 16RE

Explanation of Solution

DTD for Invoice:

<!--Declaring invoice DTD-->

<!DOCTYPE invoice [

<!--Declaring invoice element with three attributes-->

<!ELEMENT invoice (number, address, items)>

<!--Declaring number with text data-->

<!ELEMENT number (#PCDATA)>

<!--Expanding the address element with 6 attributes-->

<!ELEMENT address (name, company, street, city, state, zip)>

<!--Declaring name, company, street, city, state, and zip with text data-->

<!ELEMENT name (#PCDATA)>

<!ELEMENT company (#PCDATA)>

<!ELEMENT street (#PCDATA)>

<!ELEMENT city (#PCDATA)>

<!ELEMENT state (#PCDATA)>

<!ELEMENT zip (#PCDATA)>

<!--Setting condition an invoice may contain multiple items-->

<!ELEMENT items (item*)>

<!--Expanding item element with 2 attributes-->

<!ELEMENT item (product, quantity)>

<!--Expanding product element with 2 attributes-->

<!ELEMENT product (description, price)>

<!--Declaring description, price, quantity with text data-->

<!ELEMENT description (#PCDATA)>

<!ELEMENT price (#PCDATA)>

<!ELEMENT quantity (#PCDATA)>

<!--Closing the invoice DTD-->

]>

Explanation:

• To design the DTD for invoice, first identify the elements for invoice...