1. ‫أكاديمية الحكومة اإللكترونية الفلسطينية‬
The Palestinian eGovernment Academy
www.egovacademy.ps
Tutorial II: Data Integration and Open Information Systems
Session 2
XML DTD’s
Dr. Ismail M. Romi
Palestine Polytechnic University
PalGov © 2011 1

2. About
This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the
Commission of the European Communities, grant agreement 511159-TEMPUS-1-
2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps
Project Consortium:
Birzeit University, Palestine
University of Trento, Italy
(Coordinator )
Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium
Palestine Technical University, Palestine
Université de Savoie, France
Ministry of Telecom and IT, Palestine
University of Namur, Belgium
Ministry of Interior, Palestine
TrueTrust, UK
Ministry of Local Government, Palestine
Coordinator:
Dr. Mustafa Jarrar
Birzeit University, P.O.Box 14- Birzeit, Palestine
Telfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011
2

3. © Copyright Notes
Everyone is encouraged to use this material, or part of it, but should
properly cite the project (logo and website), and the author of that part.
No part of this tutorial may be reproduced or modified in any form or by
any means, without prior written permission from the project, who have
the full copyrights on the material.
Attribution-NonCommercial-ShareAlike
CC-BY-NC-SA
This license lets others remix, tweak, and build upon your work non-
commercially, as long as they credit you and license their new creations
under the identical terms.
PalGov © 2011 3

4. Tutorial Map
Topic h
Intended Learning Objectives
Session 1: XML Basics and Namespaces 3
A: Knowledge and Understanding
Session 2: XML DTD’s 3
2a1: Describe tree and graph data models.
Session 3: XML Schemas 3
2a2: Understand the notation of XML, RDF, RDFS, and OWL.
Session 4: Lab-XML Schemas 3
2a3: Demonstrate knowledge about querying techniques for data
models as SPARQL and XPath. Session 5: RDF and RDFs 3
2a4: Explain the concepts of identity management and Linked data. Session 6: Lab-RDF and RDFs 3
2a5: Demonstrate knowledge about Integration &fusion of Session 7: OWL (Ontology Web Language) 3
heterogeneous data. Session 8: Lab-OWL 3
B: Intellectual Skills Session 9: Lab-RDF Stores -Challenges and Solutions 3
2b1: Represent data using tree and graph data models (XML & Session 10: Lab-SPARQL 3
RDF). Session 11: Lab-Oracle Semantic Technology 3
2b2: Describe data semantics using RDFS and OWL. Session 12_1: The problem of Data Integration 1.5
2b3: Manage and query data represented in RDF, XML, OWL. Session 12_2: Architectural Solutions for the Integration Issues 1.5
2b4: Integrate and fuse heterogeneous data. Session 13_1: Data Schema Integration 1
C: Professional and Practical Skills Session 13_2: GAV and LAV Integration 1
2c1: Using Oracle Semantic Technology and/or Virtuoso to store Session 13_3: Data Integration and Fusion using RDF 1
and query RDF stores. Session 14: Lab-Data Integration and Fusion using RDF 3
D: General and Transferable Skills
2d1: Working with team. Session 15_1: Data Web and Linked Data 1.5
2d2: Presenting and defending ideas. Session 15_2: RDFa 1.5
2d3: Use of creativity and innovation in problem solving.
2d4: Develop communication skills and logical reasoning abilities. Session 16: Lab-RDFa 3
PalGov © 2011 4

5. Session ILO’s:
After completing this session students will be able to:
•Manage data represented in XML.
•Represent data using tree and graph data models.
PalGov © 2011 5

6. Session2: Document Type Definition-DTD
Session Overview:
</Create DTDs>
< Validate an XML document
against a DTD />
<Use DTDs to create XML documents
from multiple files />
PalGov © 2011 6

7. XML Schemas
 A quality control tool.
 Describes the structure of an XML document.
 Ensures that a document fulfills a minimum set of
requirements.
 Serve as away to formalize an application to be
publishable object.
 XML schema is like a program that tells a processor how
to read the document.
PalGov © 2011 7

8. A history of schema Language
1. Document Type Definition – DTD:
– The oldest and most widely supported schema language.
2. The W3C Built XML Schema:
– XML Schemas are themselves XML documents.
3. RELAX NG
4. Schemarton
PalGov © 2011 8

9. Validation Steps
A "Valid" XML document is a "Well Formed" XML document, which also
conforms to the rules of a Document Type Definition.
1. The processor reads the rules and declaration in the schema.
2. Build a specific type of parser (validating parser)
3. The validating parser take an XML instance as input.
4. Produces a validation report.
PalGov © 2011 9

10. Document Type Definition - DTD
 Defines the legal building blocks of an XML document.
 Defines the document structure with a list of legal elements and
attributes.
 DTD's are extensible - meaning they can be extended to meet the
needs of the current task.
 A DTD can be specified within an XML document (internal) or in a
separate file (external).
 Many free DTD's exist on the internet today and can be freely
downloaded.
 DTD's declare a set of allowed elements.
PalGov © 2011 10

11. Document Type Definition - DTD
 DTD's define a content model for each element: This
describes what elements or data can go inside an
element, in what order, in what number, and whether they
are required or optional.
 DTD's declare a set of allowed attributes for each element
with data types and default values.
 DTD's provide mechanisms to manage the model,
providing links to other components.
 The Document Type Declaration
 Internal DTD declaration:
 The DTD declared inside the XML file.
 External DTD declaration:
 The DTD declared in an external file.
PalGov © 2011 11

12. Internal DTD Declaration
<!DOCTYPE root-element [element-declaration ]>
Example:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE note
[
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note> PalGov © 2011 12

13. External DTD Declarations
 You can refer to an external DTD in one of the
following two ways:
– System identifiers
– Public identifiers
PalGov © 2011 13

14. External DTD Declarations using System
Identifiers
<!DOCTYPE root-element SYSTEM “system identifier” [...]>
 System identifier is a file reference, consists of:
– The keyword SYSTEM
– URI reference pointing to the document‘s location.
• A URI can be a file on your local hard drive, a file on your intranet or
network, or even a file available on the Internet:
Examples:
<!DOCTYPE name SYSTEM ―/user/local/dtds/name.dtd‖ [ ]>
<!DOCTYPE name SYSTEM ―http://wiley.com/hr/name.dtd‖ [ ]>
<!DOCTYPE name SYSTEM ―name.dtd‖>
PalGov © 2011 14

15. External DTD Declarations using Public
Identifiers
<!DOCTYPE root-element PUBLIC “public identifier” [...]>
 Public identifiers are used to identify an entry in a catalog.
 A commonly used format is called Formal Public Identifiers (FPIs).
 The syntax for an FPI is defined in the document ISO9070.
 FPI Syntax:
“-//Owner//Class Description//Language//Version”
 Example:
 <!DOCTYPE name PUBLIC ―-//Beginning XML//DTD Name Example//EN‖>
 Recommended list of DOCTYPE at:
http://www.w3.org/QA/2002/04/valid-dtd-list.html
PalGov © 2011 15

16. Sharing Vocabularies
 It is often better to share vocabularies and use DTDs that are widely
accepted.
 Sharing DTDs enables you to more easily integrate with other
companies and XML developers who use the shared vocabularies.
 Many individuals and industries have developed DTDs.
 Examples:
– Chemical Markup Language (CML) DTD
– XHTML, maintains three DTDs (Transitional, Strict, and Frameset).
 You can check many places when trying to find a DTD for a specific
industry.
– http://xml.coverpages.org/.
– http://www.dublincore.org.
PalGov © 2011 16

17. Anatomy of a DTD
 DTDs consist of three basic parts:
1. Element declarations
2. Attribute declarations
3. Entity declarations
 Those declarations must follow DOCTYPE
declaration as follow:
<?xml version 1.0, standalone = “yes”>
<!DOCTYPE root-element [
declarations
declarations
]>
PalGov © 2011 17

18. Element Declarations
 ELEMENT declaration is used to indicate to the parser that
you are about to define an element.
 The declaration can appear only within the context of the
DTD.
 Syntax
<!ELEMENT element-name (content model)>
 Element declarations consist of three basic parts:
– ELEMENT Key word (<!ELEMENT)
– Element name
– Element content model
PalGov © 2011 18

19. Element Declarations…Cont
 An element‘s content model defines the allowable
content within the element.
 An element may contain element children, text, a
combination of children and text, or the element
may be empty.
 Four kinds of content models exist:
– Element content
– Mixed content
– Empty content
– Any content
PalGov © 2011 19

20. Element Content
 Include the allowable elements within
parentheses.
 Example:
<!ELEMENT contact (name, location, phone)>
 Each element that you specify within this
element‘s content model must also have its own
definition within the DTD.
PalGov © 2011 20

21. Element Content…Cont
 The processor needs this information so that it knows how
to handle each element when it is encountered.
 Name in the content model must appear exactly as it will in
the document.
 Ways of specifying the element children:
– Sequences
– Choices
PalGov © 2011 21

22. Element Content - Sequences
 The elements within these documents must appear in a
distinct order.
 If your XML document were missing one of the elements
within the sequence, or if your document contained more
elements, the parser would raise an error.
 If all of the specified elements were included within the
XML document but appeared in another order processor
would raise an error.
 whitespace doesn‘t matter.
PalGov © 2011 22

23. Element Content - Choices
 Sometimes you needed to allow one element or
another, but not both.
 You would need a choice mechanism of some sort.
 Example:
<!ELEMENT location (address | GPS)>
 This declaration would allow the <location> element to
contain one <address> or one <GPS> element.
 If the <location> element were empty, or if it contained
more than one of these elements, the parser would
raise an error.
PalGov © 2011 23

24. Mixed Content
 The XML Recommendation specifies that any element with
text in its content is a mixed content model element.
 Within mixed content models, text can appear by itself or it
can be interspersed between elements.
 The simplest mixed content model—text only:
<!ELEMENT element-name (#PCDATA)>
 #PCDATA keyword, (Parsed Character DATA):
– indicates that the character data within the content model
should be parsed by the parser.
– Used for text or character data.
PalGov © 2011 24

25. Mixed Content - Cont
 Every time you declare elements within a mixed
content model, they must follow four rules:
– They must use the choice mechanism (the vertical bar |
character) to separate elements.
– The #PCDATA keyword must appear first in the list of
elements.
– There must be no inner content models.
– If there are child elements, the * cardinality indicator
must appear at the end of the model.
PalGov © 2011 25

26. Mixed Content-Example
DTD:
<!ELEMENT description (#PCDATA | em | strong | br)*>
XML Document:
<description>Jeff is a developer and author for Beginning XML <em>4th
edition</em>.<br/>Jeff <strong>loves</strong> XML!</description>
 The text may appear every where, and the em, strong, br can appear
any time.
Note:
em: italic, strong:bold, br: line break
PalGov © 2011 26

27. Empty Content
 Empty element doesn‘t have content.
<!ELEMENT element-name EMPTY>
 The most common used empty element is:
<br/> (line break).
PalGov © 2011 27

28. Element with ANY content
 <!ELEMENT element-name ANY>
 Can contain any combination of parsable data (text, or
elements).
 ANY: a keyword indicates that any elements declared
within the DTD can be used within the content of the
element and that they can be used in any order any
number of times.
PalGov © 2011 28

29. Cardinality
 An element‘s cardinality defines how many times it will
appear within a content model.
 Each element within a content model can have an
indicator following the element name that tells the parser
how many times it will appear.
PalGov © 2011 29

30. Cardinality…Cont
Indicator Description
None when no cardinality indicator is used, it indicates
that the element must appear once and only
once.
? Indicates that the element may appear either
once or not at all
+ Indicates that the element may appear one or
more times
* Indicates that the element may appear zero or
more times
Example:
<!ELEMENT name (first+, middle?, last), Tel*>
PalGov © 2011 30

31. Attribute Declarations
<!ATTLIST element-name attribute-name attribute-type ―attribute-value‖
 DTD example:
<!ATTLIST payment type CDATA ―check‖>
 XML example:
<payment type=―check‖>
PalGov © 2011 31

32. Attribute Types
Type Description
CDATA Indicates that the attribute value is character data
(unparsed).
ID Indicates that the attribute value uniquely identifies the
containing element.
IDREF The value is the id of another element.
IDREFS The value is a list of other ids
ENTITY The value is an entity
ENTITIES The value is a list of entities
NMTOKEN The value is a valid XML name
NMTOKENS The value is a list of valid XML names
Enumerated List The value must be an enumerated value (val1 | val2 | ….)
<!ATTLIST element-name attribute-name attribute-type “attribute-value”
PalGov © 2011 32

33. CDATA
• It specifies that the attribute value is character
data (any text).
• Unparsed content
DTD example:
<!ELEMENT square EMPTY>
<!ATTLIST square width CDATA "0">
XML example:
<square width="100">
</square>
<!ATTLIST element-name attribute-name attribute-type “attribute-value”
PalGov © 2011 33

34. ID, IDREF, and IDREFS
 Attributes of type ID can be used to uniquely identify an
element within an XML document.
 Once you have uniquely identified the element, you can
later use an IDREF to refer to that element.
 Remember several rules when using ID attributes:
– The value of an ID attribute must be unique within the entire
XML document.
– Only one attribute of type ID may be declared per element.
– The attribute value declaration for an ID attribute must be
#IMPLIED or #REQUIRED.
 The value of an IDREF attribute must match the value of some ID within the XML
document.
 To refer to a list of elements:
– Use an IDREFS attribute store with a list of whitespace-separated IDREF values that refer to
an ID attributes defined in the document.
PalGov © 2011 34

35. ENTITY and ENTITIES
• Attributes can also include references to unparsed entities.
• An unparsed entity is an entity reference to an external file
that the processor cannot parse (external images..).
• Instead of actually including the image inside the
document, you use special attributes to refer to the
external resource.
<!ATTLIST element-name attribute-name attribute-type “attribute-value”
PalGov © 2011 35

36. Enumerated Attribute Types
• Used to restrict attribute values
• An enumerated list allows you to specify a list of allowable
values.
• Each value must be a valid XML name
• Example:
DTD:
<!ATTLIST phone kind (Home | Work | Cell | Fax) #IMPLIED>
XML:
<phone kind=―Cell‖ > Valid
<phone kind=―cell‖ > Invalid
<!ATTLIST element-name attribute-name attribute-type “attribute-value”
PalGov © 2011 36

37. Attribute Value Declarations
 Within each attribute declaration you must specify how
the value will appear in the document.
 The XML Recommendation allows you to specify that the
attribute:
Value Description
#DEFAULT The attribute has a default value
#REQUIRED The attribute value must be included in the element
#IMPLIED The attribute does not have to be included
#FIXED The attribute value is fixed
<!ATTLIST element-name attribute-name attribute-type “attribute-value”
PalGov © 2011 37

38. Specifying Multiple Attributes
 Declaring each attribute:
<!ATTLIST contacts version CDATA #FIXED ―1.0‖>
<!ATTLIST contacts source CDATA #IMPLIED>
 Using one declaration:
<!ATTLIST contacts version CDATA #FIXED ―1.0‖
source CDATA #IMPLIED>
PalGov © 2011 38

39. Entities
• Place holder in XML
• Types:
– Built-in entities
– Character entities
– General entities
– Parameter entities
PalGov © 2011 39

40. Built-in Entities
• &amp; The & character
• &lt; The < character
• &gt; The > character
• &apos; The ‗ character
• &quot; The ― character
PalGov © 2011 40

41. References to Built-in Entities
 To use an entity, you must include an entity
reference within the document.
 An entity reference refers to an entity that
represents a character, some text, or even an
external file.
 A reference to a built-in entity takes the following
form:
&entity-name;
 Example:
<CheckAvg> Avg &lt; ―85‖ </CheckAvg>
PalGov © 2011 41

42. Character Entities
• Used for characters that are difficult to type.
• Not found on the keyboard.
&#unicode-value;
• Example:
&#169; === character c
• Using Hexadecimal values:
• Example: you must include a lowercase x
&#x00A9; === character c before the value, so that the
XML parser knows how it
should handle the reference.
PalGov © 2011 42

43. General Entities ( Internal Entities)
 Variables used to define shortcuts to standard text
or special characters.
 General entities must be declared within the DTD
before they can be used within the XML
document.
 Declaration:
– <!ENTITY entity-name ―value‖>
 Example:
DTD – <!ENTITY address ―Palestine, Hebron, POBox 198‖>
XML– <ppu-address> &address; </ppu-address>
PalGov © 2011 43

44. External Entities
• Entity whose replacement text exists in another file.
• Useful for:
– Importing content that is shared by many documents.
– Importing content that is changed frequently.
– Breaking the document into multiple physical parts.
• External entities must be declared in order to enable the
parser find the replacement text.
PalGov © 2011 44

45. External Entities…Cont
• Declaration:
– <!ENTITY entity-name SYSTEM ―Physical location‖>
• Example:
– <!ENTITY countries System ―d://countries.xml‖>
PalGov © 2011 45

46. Unparsed Entities
• Holds content that should not be parsed
because it contains something other than
text or xml.
• Useful for:
– Importing graphics, sound files.
– None character data.
• Declaration:
<!ENTITY entity-name SYSTEM ―physical location‖ NDATA file-format>
PalGov © 2011 46

47. Unparsed Entities…Cont
• Example:
DTD
<!ENTITY pic1 SYSTEM ―c://pic.git‖ NDATA GIF>
XML
<picture> &pic1; </picture>
PalGov © 2011 47

48. DTD Limitations
• Differences between DTD syntax and XML syntax.
• Poor support for XML namespaces
• Poor data typing.
• Limited content model descriptions.
PalGov © 2011 48

49. Summary
• By using DTDs, you can easily validate your XML
documents against a defined vocabulary of
elements and attributes. This reduces the amount
of code needed within your application.
• An XML parser can be used to check whether the
contents of an XML document are valid according
to the declarations within a DTD.
PalGov © 2011 49

50. Refrences
• Hunter, H, Rafter, J., Fawcett, J., Vlist, E., Ayers, D., Duckett, J., Watt,
A., McKinnon,L., (2007), "Beginning XML", 4th Ed.,Wiley Publishing
Inc: Indiana, USA.
• Ray, E., (2003), "Learning XML", 2nd Ed., O‘Rreilly Media Inc.: USA.
• Amiano, M., D'Cruz, C., Ethier, K., Thomas, M., (2006), XML:
Problem - Design – Solution", Wiley Publishing Inc: Indiana, USA.
• http://www.w3.org
• http://www.w3schools.com
• http://www.xml.com
• http://www.xml.org
PalGov © 2011 50

51. <e-Gov> Thank you </e-Gov>
PalGov © 2011 51