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XML (2)

XML (2). DTD Sungchul Hong. <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE simple [ <!ELEMENT DOCUMENT (#PCDATA)> <!ATTLIST DOCUMENT trackNum CDATA #REQUIRED secLevel (unclassified|classified) "unclassified"> <!ENTITY Description "This is a very simple

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XML (2)

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  1. XML (2) DTD Sungchul Hong

  2. <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE simple [ <!ELEMENT DOCUMENT (#PCDATA)> <!ATTLIST DOCUMENT trackNum CDATA #REQUIRED secLevel (unclassified|classified) "unclassified"> <!ENTITY Description "This is a very simple sample document."> ]> <DOCUMENT trackNum="1234">This is an entity inside an element:&Description; </DOCUMENT>

  3. Document Type Definition • A DTD is used to validate an XML document. • Only one DTD per document • Document type declaration • <!DOCTYPE name […]> • XML documents • Well formed documents • Document must comply with the XML specification. • Valid documents • A valid document is a document that has a DTD and follows the rule laid out in that DTD.

  4. Document Type Declarations • <! DOCTYPE JU:LunchMenu SYSTEM http://catering.com/menus/lunch/Menu.DTD> • <!DOCTYPE JU:LunchMenu PUBLIC “/lunch/Menu.DTD”>

  5. Internal DTD Subset • A DTD can be declared internal to the XML document • Internal subsets are parsed before external subsets • Internal declarations that match external declarations will override the corresponding declarations.

  6. <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE simple [ <!ELEMENT DOCUMENT (TITLE,AUTHOR+,SUMMARY*,NOTE?)> <!ATTLIST DOCUMENT trackNum CDATA #REQUIRED secLevel (unclassified|classified) "unclassified"> <!ELEMENT TITLE (#PCDATA)> <!ELEMENT AUTHOR (#PCDATA)> <!ELEMENT SUMMARY (#PCDATA)> <!ENTITY Description "This is a very simple sample document."> ]> <DOCUMENT trackNum="1234"> <TITLE>Sample Document</TITLE> <AUTHOR>Simon St.Laurent</AUTHOR> <SUMMARY>This is an entity inside an element:&Description; </SUMMARY></DOCUMENT>

  7. External DTD Subset • The Document Type Declaration will now provide a URL and either a system or public identifier • Provides more flexibility than internal DTD subsets • <! DOCTYPE JU:LunchMenu SYSTEM http://catering.com/menus/lunch/Menu.DTD> • <!DOCTYPE JU:LunchMenu PUBLIC “/lunch/Menu.DTD”>

  8. <?xml version="1.0" standalone="no""UTF-8"?> <!DOCTYPE SIMPLE SYSTEM "http://127.0.0.1/simple.dtd"> <SIMPLE> <DOCUMENT trackNum="1234"> <TITLE>Sample Document</TITLE> <AUTHOR><FIRSTNAME>Simon</FIRSTNAME> <LASTNAME>St.Laurent</LASTNAME> <COMPANY>XML Mania</COMPANY> </AUTHOR> <SUMMARY>This is an entity inside an element:&Description; </SUMMARY> </DOCUMENT> </SIMPLE>

  9. Elements • <!ELEMENT name data> • <!ELEMENT DOCUMENT (TITLE,AUTHOR+,SUMMARY*,NOTE?)> • Declares what elements are legal, what order they should appear in and the number of elements • Data can be one of five types: Empty, Elements-only, Characters-only, any and mixed.

  10. Elements • Empty: the corresponding element cannot contain either text or other elements • <!ELEMENT price EMPTY> • Element-only: the corresponding element can only contain other elements, no text. • <!ELEMENT person (name, address, tel)> • Characters-only: The corresponding element can contain only text • <!ELEMENT bookinfo (#PCDATA) > • Any: the corresponding element can include any of previous three types • <!ELEMENT other ANY> • Mixed: the corresponding element must have both elements and text • <!ELEMENT mixedup (e1, e2) (#PCDATA)>

  11. Elements Syntax • Content model • ( ): substructure • , : strict ordering • | : choice • ?: optional • *: zero or more of a particular item can appear. • +: The plus-sign (+) denotes that one or more of a particular item can appear.

  12. Example <!ELEMENT DOCUMENT (TITLE,AUTHOR+,SUMMARY*,NOTE?)> <!ELEMENT User (Name, Email | Phone))> <!ELEMENT Blah (A, (B?, C)*, D+, (E|F)>

  13. Attributes Syntax • A DTD defines attributes with the <!ATTLIST …> declaration. • <!ATTLIST element attribute CDATA #required> • #REQUIRED-the attribute must appear with this element. • #IMLIED- the attribute may appear with this element. • #FIXED default value – the attribute must always have the default value. If it does not appear explicitly, it is assumed. • Default value – the attribute may appear with the default or can have another value.

  14. Attribute Types • CDATA – Character data. Used if an attribute value is only plain text. • <!ATTLIST Order order_num CDATA #REQUIRED> • <order order_num = “123abc”> … </order>

  15. Attribute Types • ID – unique name within a document used to uniquely identify an element. • <!ATTLIST Order order_num ID #REQUIRED> • <Order order_num = “123abc”> .. </order> • <order order_num = “456def”> …</order>

  16. Attribute Types • IDREF- A reference to an element with an ID, allowing for links to b created within documents. • <!ATTLIST Order order_num ID #REQUIRED> • <!ATTLIST ClosedOrder order_ref IDREF #REQUIRED> • <Order order_num = “123abc”>… </Order> • <ClosedOrder order_ref = “123abc”/>

  17. Attribute Types • IDREFS – Series of references to elements with corresponding Ids • <!ELEMENT ClosedOrders EMPTY> • <!ATTLIST Order order_num ID #REQUIRED> • <!ATTLIST ClosedOrders order_ref IDREFS #REQUIRED> • <Order order_num = “123abc”>… </Order> • <Order order_num = “456def”>… </Order> • <ClosedOrders order_ref = “123abc 456def”/>

  18. Enumerated Values • Enumerated values are defined with not type definition. • A parenthetical sequence of legal values is given instead • Do not use quotation marks and remember the values are case sensitive • <!ATTLIST JU:Dessert type (regular | lowfat | sugar-free) #REQUIRED> • <JU:Dessert type = “lowfat”>Cheescake</JU:Dessert>

  19. NOTATION • NOTATION- Identify the format of external data items that we wish to use with our XML document • <!NOTATION gif SYSTM “imageviewer.exe”>

  20. Entities • Entities allow you t declare content and reference it anytime you need it within a document • Entities are like an alias to some content • Predefined entities &lt, &gt, &amp, &apos, &quote

  21. <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE simple [ <!ELEMENT DOCUMENT (#PCDATA)> <!ATTLIST DOCUMENT trackNum CDATA #REQUIRED secLevel (unclassified|classified) "unclassified"> <!ENTITY Description "This is a very simple sample document."> ]> <DOCUMENT trackNum="1234">This is an entity inside an element:&Description; </DOCUMENT>

  22. Problems With DTD • DTD use a non-XML syntax. • There is no way to type information like numbers • DTDs do not allow merging of documents • XML Schema

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