this presentation covers 1. declaring elements 2. control characters 3. dtd attributes and entities

2. 1. Declaring elements
• XML document has number of elements.
• The first node of XML document is called
the root node.
Syntax: <!ELEMENT element-type category>
Ex: <!ELEMENT name(fname, lname)*>

3. Control characters
• Item*
• (item1,item2,item3)
• Item
• (item1,item2)
• (item1/item2)
• Item+
• Item?
• Appears zero or more times.
• Separates items in a sequence.
• Appears exactly once.
• Closes a group of items.
• Only one may appear.
• Appears at least once.
• Appears once or not at all.
Ex: <!ELEMENT recipe(name, ingredients+ ,cooking+ serves?, instruction*)>

4. 2. DTD attributes
• Attributes are additional information
associated with an element type.
• ATTLIST is used to identify attributes for
elements.
• Syntax: <!ATTLIST element-name attribute-
name attribute-type default-value>
<element attribute-name=“attribute-value”>

5. • Ex:
<?xml version=“1.0”>
<!DOCTYPE image[
<!ELEMENT image EMPTY>
<!ATTLIST image height CDATA #REQUIRED>
<!ATTLIST image width CDATA #REQUIRED>
]>
<image height=“32” width=“32”>

6. 3. DTD entities
• It is a symbolic representation of information.
• Mark up elements that contains complex data
are often referred as entities.
• Entities are variables used to define shortcuts
to text and special characters.
• They are internal and external.

7. 1. Internal entity
• Refers to data that an XML processor has to
parse.
• Syntax: <!ENTITY name “entity value”>
Ex:
<?xml version=“1.0”>
<!DOCTYPE letter[
<!ENTITY hbd “happy birth day”>
]>
<letter> &hbd;</letter>

8. 2. External entity
• Used for creating a common reference
that can be shared between multiple
documents.
• There are two types: private and public
• Syntax:
<!ENTITY name SYSTEM “URL/URI”>
<!ENTITY name PUBLIC “publicID” “URI”>