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--- tanszek:oktatas:techcomm:dtd [2024/10/07 17:46] – [Example: An album has at least one title, followed by at least one **track title** and **duration**:] knehez
+++ tanszek:oktatas:techcomm:dtd [2024/10/07 17:57] (current) – [Complex DTD Example for a Hypothetical Mail Processing System] knehez
@@ Line 105: / Line 105: @@
 </CD>
 </sxh>
+----
 ==== Example: An album has at least one title, followed by at least one **track title** and **duration**: ====
@@ Line 130: / Line 130: @@
 </sxh>
----
+----
 ==== Example: A library may contain **books** (zero or more)====
@@ Line 158: / Line 158: @@
 </sxh>
+===== Defining Attributes in DTD =====
+If a class has an attribute such as "number of students," it can be specified as follows:
+<sxh>
+<!ELEMENT class (student *) >
+<!ATTLIST class number CDATA #REQUIRED>
+</sxh>
+Attributes can be:
+- **#IMPLIED**: not mandatory
+- **#REQUIRED**: mandatory
+- **#FIXED**: fixed value
+=== Specifying a Default Attribute Value ==
+Example:
+<sxh>
+<!ATTLIST paymentType type CDATA "bankTransfer">
+</sxh
+The XML could look like this:
+<sxh>
+<paymentType/> or <paymentType type="bankTransfer">
+</sxh>
+=== Enumerated Values ===
+**Syntax**:
+<sxh>
+<!ATTLIST element-name attribute-name (eval | eval | ..) default-value>
+</sxh>
+**DTD Example**:
+<sxh>
+<!ATTLIST payment type (check | cash) "cash">
+</sxh>
+**XML Example**:
+<sxh xml>
+<payment type="check"/> or <payment type="cash"/>
+</sxh>
+==== Complex DTD Example for a Hypothetical Mail Processing System ====
+**Task**: Provide an XML example that satisfies the following DTD:
+<sxh>
+<!ELEMENT mails (email*, postcard*)>
+<!ELEMENT email (address, sender, message?, attachment?)>
+<!ELEMENT postcard (address, sender?, message?)>
+<!ELEMENT address (name, postalcode, city, country)>
+<!ATTLIST address nick CDATA #IMPLIED>
+<!ATTLIST sender nick CDATA #IMPLIED>
+<!ATTLIST attachment type CDATA #REQUIRED>
+<!ATTLIST postcard scanimage CDATA #IMPLIED>
+<!ATTLIST sender name CDATA #REQUIRED>
+</sxh>
+=== A Possible XML for the given DTD ===
+<sxh xml>
+<mails>
+    <email>
+        <address nick="Alice">alice@usa.com</address>
+        <sender nick="Bob">bob@jp.com</sender>
+        <message>Hash code</message>
+        <attachment type="text/doc"></attachment>
+    </email>
+    <postcard scanimage="kep.jpg">
+       <address>
+         <name>John Doe</name>
+         <postalcode>1234</postalcode>
+         <city>Miskolc</city>
+         <country>Hungary</country>
+       </address>
+       <sender name="Bob Cat" />
+       <message>Happy Name Day</message>
+    </postcard>
+</mails>
+</sxh>
+This provides an example of how attributes, including mandatory, optional, and default values, can be defined in a DTD and represented in an XML document.