1. XML
28-Dec-17

2. What is XML? XML stands for EXtensible Markup Language
XML is a markup language much like HTML
More accurately defined as a metalanguage
XML was designed to describe data

3. Historical Development
SGML( Standard Generalized Markup Language)
XML
HTML
MusicXML
. . .
MathML
XHTML
CML
RSS
XBRL
Comp Sci 346
12/28/2017

4. What is XML?
XML tags are not predefined. You define your own tags depending on the application
XML uses a Document Type Definition (DTD) or an XML Schema to describe the data
XML with a DTD or XML Schema is designed to be self- descriptive
XML is a W3C Recommendation

5. Difference Between XML and HTML
XML was designed to carry data.
XML is not a replacement for HTML.
XML and HTML were designed with different goals:
XML was designed to describe data and to focus on what data is.
HTML was designed to display data and to focus on how data looks.
HTML is about displaying information, while XML is about describing information.

6. XML Does Not DO Anything
XML was not designed to DO anything.
XML was created to structure, store and to send information.

7. More XML XML is free and extensible
XML tags are not predefined. You must "invent" your own tags.
The tags used to mark up HTML documents and the structure of HTML documents are predefined.
XML allows the author to define their own tags and their own document structure.
The tags in the example above (like <to> and <from>) are not defined in any XML standard. These tags are "invented" by the author of the XML document.

8. XML is a Complement to HTML
It is important to understand that XML is not a replacement for HTML. In future Web development it is most likely that XML will be used to describe the data, while HTML will be used to format and display the same data.
XML is a cross-platform, software and hardware independent tool for transmitting information.

9. XML Can Separate Data from HTML
With XML, your data is stored outside your HTML.
When HTML is used to display data, the data is stored inside your HTML.
With XML, data can be stored in separate XML files. This way you can concentrate on using HTML for data layout and display, and be sure that changes in the underlying data will not require any changes to your HTML.

10. XML is Used to Exchange Data
With XML, data can be exchanged between incompatible systems.
Computer systems and databases contain data in incompatible formats. One of the most time-consuming challenges for developers has been to exchange data between such systems over the Internet.
Converting the data to XML can greatly reduce this complexity and create data that can be read by many different types of applications.

11. XML Can Be Used to Share Data
Since XML data is stored in plain text format, XML provides a software- and hardware-independent way of sharing data.
This makes it much easier to create data that different applications can work with. It also makes it easier to expand or upgrade a system to new operating systems, servers, applications, and new browsers. 

12. XML Can Be Used to Store Data
With XML, plain text files can be used to store data.
XML can also be used to store data in files or in databases. Applications can be written to store and retrieve information from the store, and generic applications can be used to display the data.

13. Editors XML files can be edited using any text editor:
Windows: Notepad, NotePad++, EditPad Lite, etc
Mac OS: Text Wrangler, BBEdit, TextMate
Linux: Emacs, VIM, Pico, etc.

14. Viewing XML Files in a Web Browser
XML documents can be opened in Internet Explorer or in Firefox.
If there are no syntax errors:
IE and Firefox will display the document’s contents in an expandable/collapsible outline format including all markup tags.

15. Style Sheets & XML
There are two main style sheet languages used with XML:
Cascading Style Sheets (CSS) and Extensible Style Sheets (XSL)
The important benefits to using style sheets are the same as using them with XHTML docs.

16. A sample XML document <?xml version="1.0" encoding=“UTF-8"?>
<customers>
<name>Fred Flintstone</name>
<street>123 Main St.</street>
<city>Lansing</city>
<state>MI</state>
<zip>48901</zip>
<phone> </phone>
</customers>

17. Introduction to XML XML stands for EXtensible Markup Language
XML is a markup language much like HTML
XML was designed to carry data, not to display data
XML tags are not predefined. You must define your own tags
XML is designed to be self-descriptive
XML is a W3C Recommendation

18. XML is Not a Replacement for HTML
It is important to understand that XML is not a replacement for HTML. In most web applications, XML is used to transport data, while HTML is used to format and display the data.

19. With XML You Invent Your Own Tags
The tags used in HTML are predefined. HTML documents can only use tags defined in the HTML standard (like <p>, <h1>, etc.).
XML allows the author to define his/her own tags and his/her own document structure.

20. XML Separates Data from HTML
If you need to display dynamic data in your HTML document, it will take a lot of work to edit the HTML each time the data changes.
With XML, data can be stored in separate XML files. This way you can concentrate on using HTML/CSS for display and layout, and be sure that changes in the underlying data will not require any changes to the HTML.
With a few lines of JavaScript code, you can read an external XML file and update the data content of your web page.

21. XML Simplifies Data Transport
One of the most time-consuming challenges for developers is to exchange data between incompatible systems over the Internet.
Exchanging data as XML greatly reduces this complexity, since the data can be read by different incompatible applications.

22. HTML and XML, I XML stands for eXtensible Markup Language
HTML is used to mark up text so it can be displayed to users
XML is used to mark up data so it can be processed by computers
HTML describes both structure (e.g. <p>, <h2>, <em>) and appearance (e.g. <br>, <font>, <i>)
XML describes only content, or “meaning”
In XML, you make up your own tags
HTML uses a fixed, unchangeable set of tags

23. Difference between XML and HTML
XML was designed to carry data, not displaying data
XML is not a replacement for HTML.
Different goals:
XML was designed to describe data and to focus on what data is. HTML was designed to display data and to focus on how data looks.
HTML is about displaying information, XML is about describing information.
XML Introdution

24. An example of XML <?xml version="1.0"?> <products>
<product id="PRO001">
<name>Coca Cola</name>
<price>5000</price>
</product>
<product id="PRO002">
<name>Pepsi</name>
<price>4500</price>
<product id="PRO003">
<name>Number One</name>
<price>5500</price>
</products>
XML Introdution

25. HTML and XML, II
HTML and XML look similar, because they are both SGML languages (SGML = Standard Generalized Markup Language)
Both HTML and XML use elements enclosed in tags (e.g. <body>This is an element</body>)
Both use tag attributes (e.g., <font face="Verdana" size="+1" color="red">)
Both use entities (<, >, &, ", &apos;)
More precisely,
HTML is defined in SGML
XML is a (very small) subset of SGML

26. HTML and XML, III HTML is for humans XML is for computers
HTML describes web pages
You don’t want to see error messages about the web pages you visit
Browsers ignore and/or correct as many HTML errors as they can, so HTML is often sloppy
XML is for computers
XML describes data
The rules are strict and errors are not allowed
In this way, XML is like a programming language
Current versions of most browsers can display XML
However, browser support of XML is spotty at best

27. SGML(ISO 8879) Standard Generalized Markup Language
The international standard for defining descriptions of structure and content in text documents
Interchangeable: device-independent, system-independent
Tags are not predefined
Using DTD to validate the structure of the document
Large, powerful, and very complex
Heavily used in industrial and commercial for over a decade
XML Introdution

28. HTML(RFC 1866) HyperText Markup Language
A small SGML application used on web (a DTD and a set of processing conventions)
Can only use a predefined set of tags
XML Introdution

29. What Is XML? eXtensible Markup Language A simplified version of SGML
Maintains the most useful parts of SGML
Designed so that SGML can be delivered over the Web
XHTML -- a reformulation of HTML 4 in XML 1.0
XML Introdution

30. XML Syntax All XML elements must have a closing tag
XML tags are case sensitive
All XML elements must be properly nested
All XML documents must have a root tag
Attribute values must always be quoted
With XML, white space is preserved
With XML, a new line is always stored as LF
XML Introdution

31. XML-related technologies
DTD (Document Type Definition) and XML Schemas are used to define legal XML tags and their attributes for particular purposes
CSS (Cascading Style Sheets) describe how to display HTML or XML in a browser
XSLT (eXtensible Stylesheet Language Transformations) and XPath are used to translate from one form of XML to another
DOM (Document Object Model), SAX (Simple API for XML, and JAXP (Java API for XML Processing) are all APIs for XML parsing

32. Example XML document <?xml version="1.0"?> <weatherReport>
<date>7/14/97</date>
<city>North Place</city>, <state>NX</state>
<country>USA</country>
High Temp: <high scale="F">103</high>
Low Temp: <low scale="F">70</low>
Morning: <morning>Partly cloudy, Hazy</morning>
Afternoon: <afternoon>Sunny & hot</afternoon>
Evening: <evening>Clear and Cooler</evening>
</weatherReport>

33. The Basic Rules XML is case sensitive
<Message>This is incorrect</message>
<message>This is correct</message>

34. The Basic Rules Empty Element All start tags must have end tags
<composer>Mozart
<composer>Mozart</composer>
Empty Element
<BR></BR>
<BR/>
<img align=“center” src=“logo.gif”/>
<composer name=“Mozart”></composer>
<composer name=“Mozart”/>

35. The Basic Rules Elements must be properly nested
<b><i>This is incorrect nesting</b></i>
<b><i>This is correct nesting</i></b>

36. The Basic Rules
XML declaration must be the first statement
<?xml version="1.0" encoding="ISO " stAandalone="yes"?>

37. The Basic Rules <root> <child>
Every document must contain a root element
<root>
<child>
<subchild>.....</subchild>
</child>
</root>

38. The Basic Rules <note date="12/11/2007">
Attribute values must be quoted with inverted commas
<note date="12/11/2007">
<to>Ani</to>
<from>John</from>
</note>

39. The Basic Rules Certain characters are reserved for parsing
<message>if salary < 1000 then</message>

40. Predefined entities < less than > greater than & &
&ampersand
&apos; '
apostrophe
"
"
quotation mark

41. XML Building blocks--Prolog
The part of an XML document that precedes the XML data
Includes
A declaration: version [, encoding, standalone]
An optional DTD (Document Type Definition )
Example
<?xml version=“1.0” encoding=“UTF-8” standalone=“yes”?>
XML Introdution

42. Tags Tags are used to specify a name for a given piece of information.
A tag consists of opening and closing angular brackets (<>) that enclose the name of the tag.
Example
<EMP_NAME>Nick Shaw</EMP_NAME>
XML Introdution

43. Elements Elements are represented using tags.
An XML document must always have a root element.
General format:
<element> … </element>
Empty element:
<empty-Element />
Example
<Authorname>John Smith</Authorname>
XML Introdution

44. XML Elements are Extensible
XML documents can be extended to carry more information
XML Elements have Relationships
Elements are related as parents and children
Elements have Content
Elements can have different content types: element content, mixed content, simple content, or empty content and attributes
XML elements must follow the naming rules
XML Introdution

45. Content
Content refers to the information represented by the elements of an XML document.
Character or data content
Element content
Combination or mixed content
Example
<BOOKNAME>The Painted House</BOOKNAME>
XML Introdution

46. Attributes Located in the start tag of elements
Provide additional information about elements
Often provide information that is not a part of data
Must be enclosed in quotes
Should I use an element or an attribute?
metadata (data about data) should be stored as attributes, and that data itself should be stored as elements
XML Introdution

47. Entities An entity is a name that is associated with a block of data..
Internal Entities: < , >…
General Entities
General entities are declared in Document Type Definitions (DTD)
Example
<! ENTITY nyt "The Times of India.">
For more information, please visit &nyt; Thank you!
Parameter Entities
Are only declared and used in DTDs
<!ENTITY % bool ("yes | no")>
<ATTLIST membership (%bool;)>
XML Introdution

48. Overall structure
An XML document may start with one or more processing instructions (PIs) or directives:
<?xml version="1.0"?> <?xml-stylesheet type="text/css" href="ss.css"?>
Following the directives, there must be exactly one root element containing all the rest of the XML:
<weatherReport> </weatherReport>

49. XML building blocks
Aside from the directives, an XML document is built from:
elements: high in <high scale="F">103</high>
tags, in pairs: <high scale="F">103</high>
attributes: <high scale="F">103</high>
entities: <afternoon>Sunny & hot</afternoon>
character data, which may be:
parsed (processed as XML)--this is the default
unparsed (all characters stand for themselves)

50. Elements and attributes
Attributes and elements are somewhat interchangeable
Example using just elements:
<name> <first>David</first> <last>Matuszek</last> </name>
Example using attributes:
<name first="David" last="Matuszek"></name>
You will find that elements are easier to use in your programs--this is a good reason to prefer them
Attributes often contain metadata, such as unique IDs
Generally speaking, browsers display only elements (values enclosed by tags), not tags and attributes

51. Well-formed XML
Every element must have both a start tag and an end tag, e.g. <name> ... </name>
But empty elements can be abbreviated: <break />.
XML tags are case sensitive
XML tags may not begin with the letters xml, in any combination of cases
Elements must be properly nested, e.g. not <b><i>bold and italic</b></i>
Every XML document must have one and only one root element
The values of attributes must be enclosed in single or double quotes, e.g. <time unit="days">
Character data cannot contain < or &

52. Entities Five special characters must be written as entities:
& for & (almost always necessary)
< for < (almost always necessary)
> for > (not usually necessary)
" for " (necessary inside double quotes)
&apos; for ' (necessary inside single quotes)
These entities can be used even in places where they are not absolutely required
These are the only predefined entities in XML

53. XML declaration
The XML declaration looks like this: <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
The XML declaration is not required by browsers, but is required by most XML processors (so include it!)
If present, the XML declaration must be first--not even whitespace should precede it
Note that the brackets are <? and ?>
version="1.0" is required (this is the only version so far)
encoding can be "UTF-8" (ASCII) or "UTF-16" (Unicode), or something else, or it can be omitted
standalone tells whether there is a separate DTD

54. XML Encoding
XML documents can contain international characters, like Norwegian æøå, or French êèé.
To avoid errors, you should specify the encoding used, or save your XML files as UTF-8.
Unicode is an industry standard for character encoding of text documents. It defines (nearly) every possible international character by a name and a number.
Unicode has two variants: UTF-8 and UTF-16.
UTF = Universal character set Transformation Format.

55. XML Encoding
UTF-8 uses a single byte (8-bits) to represent commonly used characters and two (or three) bytes for the rest.
UTF-16 uses two bytes (16 bits) for most characters, and three bytes for the rest.
UTF-8 Web Standard
UTF-8 is the standard character encoding on the web.
UTF-8 is the default character encoding for HTML-5, CSS, JavaScript, PHP, SQL, and XML.

56. Processing instructions
PIs (Processing Instructions) may occur anywhere in the XML document (but usually first)
A PI is a command to the program processing the XML document to handle it in a certain way
XML documents are typically processed by more than one program
Programs that do not recognize a given PI should just ignore it
General format of a PI: <?target instructions?>
Example: <?xml-stylesheet type="text/css" href="mySheet.css"?>

57. Comments <!-- This is a comment in both HTML and XML -->
Comments can be put anywhere in an XML document
Comments are useful for:
Explaining the structure of an XML document
Commenting out parts of the XML during development and testing
Comments are not elements and do not have an end tag
The blanks after <!-- and before --> are optional
The character sequence -- cannot occur in the comment
The closing bracket must be -->
Comments are not displayed by browsers, but can be seen by anyone who looks at the source code

58. CDATA By default, all text inside an XML document is parsed
You can force text to be treated as unparsed character data by enclosing it in <![CDATA[ ]]>
Any characters, even & and <, can occur inside a CDATA
Whitespace inside a CDATA is (usually) preserved
The only real restriction is that the character sequence ]]> cannot occur inside a CDATA
CDATA is useful when your text has a lot of illegal characters (for example, if your XML document contains some HTML text)

59. Names in XML
Names (as used for tags and attributes) must begin with a letter or underscore, and can consist of:
Letters, both Roman (English) and foreign
Digits, both Roman and foreign
. (dot)
- (hyphen)
_ (underscore)
: (colon) should be used only for namespaces
Combining characters and extenders (not used in English)

60. Namespaces
Recall that DTDs are used to define the tags that can be used in an XML document
An XML document may reference more than one DTD
Namespaces are a way to specify which DTD defines a given tag
XML, like Java, uses qualified names
This helps to avoid collisions between names
Java: myObject.myVariable
XML: myDTD:myTag
Note that XML uses a colon (:) rather than a dot (.)

61. Review of XML rules Start with <?xml version="1"?>
XML is case sensitive
You must have exactly one root element that encloses all the rest of the XML
Every element must have a closing tag
Elements must be properly nested
Attribute values must be enclosed in double or single quotation marks
There are only five predeclared entities

62. Another well-structured example
<novel> <foreword> <paragraph> This is the great American novel </paragraph> </foreword> <chapter number="1"> <paragraph>It was a dark and stormy night </paragraph> <paragraph>Suddenly, a shot rang out! </paragraph> </chapter> </novel>

63. Valid XML You can make up your own XML tags and attributes, but...
...any program that uses the XML must know what to expect!
A DTD (Document Type Definition) defines what tags are legal and where they can occur in the XML
An XML document does not require a DTD
XML is well-structured if it follows the rules given earlier
In addition, XML is valid if it declares a DTD and conforms to that DTD
A DTD can be included in the XML, but is typically a separate document
Errors in XML documents will stop XML programs
Some alternatives to DTDs are XML Schemas and RELAX NG

64. Viewing XML
XML is designed to be processed by computer programs, not to be displayed to humans
Nevertheless, almost all current browsers can display XML documents
They don’t all display it the same way
They may not display it at all if it has errors
For best results, update your browsers to the newest available versions
Remember: HTML is designed to be viewed, XML is designed to be used

65. Displaying your XML Files with CSS
With CSS (Cascading Style Sheets) you can add display information to an XML document.
<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/css" href="cd_catalog.css"?> <CATALOG>   <CD>     <TITLE>Empire Burlesque</TITLE>     <ARTIST>Bob Dylan</ARTIST>     <COUNTRY>USA</COUNTRY>     <COMPANY>Columbia</COMPANY>     <PRICE>10.90</PRICE>     <YEAR>1985</YEAR>   </CD>
</CATALOG>

66. CATALOG { background-color: #ffffff; width: 100%; } CD display: block; margin-bottom: 30pt; margin-left: 0;

67. TITLE {
color: #FF0000;
font-size: 20pt; }
ARTIST
color: #0000FF;

68. COUNTRY,PRICE,YEAR,COMPANY{
display: block;
color: #000000;
margin-left: 20pt; }

69. Easily Processed Why Is XML Important? Plain Text Easy to edit
Platform independent
Data Identification
Tell you what kind of data you have
Can be used in different ways by different applications
Easily Processed
Vendor-neutral standard
XML Introdution

70. Inherently style-free XSL---Extensible Stylesheet Language
Why Is XML Important?
Stylability
Inherently style-free
XSL---Extensible Stylesheet Language
Different XSL formats can then be used to display the same data in different ways
Inline Reusability
Can be composed from separate entities
Modularize your documents
XML Introdution

71. Linkability -- XLink and XPointer Simple unidirectional hyperlinks
Why is XML important?
Linkability -- XLink and XPointer
Simple unidirectional hyperlinks
Two-way links
Multiple-target links
“Expanding” links
Hierarchical
Faster to access
Easier to rearrange
XML Introdution

72. XML Application1—Separate data
XML can Separate Data from HTML
Store data in separate XML files
Using HTML for layout and display
Using Data Islands
Data Islands can be bound to HTML elements
Benefits:
Changes in the underlying data will not require any changes to your HTML
XML Introdution

73. XML Application2—Exchange data
XML is used to Exchange Data
Text format
Software-independent, hardware-independent
Exchange data between incompatible systems, given that they agree on the same tag definition.
Can be read by many different types of applications
Benefits:
Reduce the complexity of interpreting data
Easier to expand and upgrade a system
XML Introdution

74. XML Application3—Store Data
XML can be used to Store Data
Plain text file
Store data in files or databases
Application can be written to store and retrieve information from the store
Other clients and applications can access your XML files as data sources
Benefits:
Accessible to more applications
XML Introdution

75. XML Application4—Create new language
XML can be used to Create new Languages
WML (Wireless Markup Language) used to markup Internet applications for handheld devices like mobile phones (WAP)
MusicXML used to publishing musical scores
RSS.
MathML.
XML Introdution

76. Overview XML and Structured Data
Pre-XML representation of data:
XML representation of the same data:
“PO-1234”,”CUST001”,”X9876”,”5”,”14.98”
<PURCHASE_ORDER>
<PO_NUM> PO-1234 </PO_NUM>
<CUST_ID> CUST001 </CUST_ID>
<ITEM_NUM> X9876 </ITEM_NUM>
<QUANTITY> 5 </QUANTITY>
<PRICE> </PRICE>
</PURCHASE_ORDER>

77. Overview Benefits of XML
Open W3C standard
Representation of data across heterogeneous environments
Cross platform
Allows for high degree of interoperability
Strict rules
Syntax
Structure
Case sensitive

78. Overview Who Uses XML? Submissions by Technologies using XML Microsoft
IBM
Hewlett-Packard
Fujitsu Laboratories
Sun Microsystems
Netscape (AOL), and others…
Technologies using XML
SOAP, ebXML, BizTalk, WebSphere, many others…

79. Syntax and Structure Components of an XML Document
Elements
Each element has a beginning and ending tag
<TAG_NAME>...</TAG_NAME>
Elements can be empty (<TAG_NAME />)
Attributes
Describes an element; e.g. data type, data range, etc.
Can only appear on beginning tag
Processing instructions
Encoding specification (Unicode by default)
Namespace declaration
Schema declaration

80. Syntax and Structure Components of an XML Document
<?xml version=“1.0” ?>
<?xml-stylesheet type="text/xsl” href=“template.xsl"?>
<ROOT>
<ELEMENT1><SUBELEMENT1 /><SUBELEMENT2 /></ELEMENT1>
<ELEMENT2> </ELEMENT2>
<ELEMENT3 type=‘string’> </ELEMENT3>
<ELEMENT4 type=‘integer’ value=‘9.3’> </ELEMENT4>
</ROOT>
Elements with Attributes
Elements
Prologue (processing instructions)

81. Syntax and Structure Rules For Well-Formed XML
There must be one, and only one, root element
Sub-elements must be properly nested
A tag must end within the tag in which it was started
Attributes are optional
Defined by an optional schema
Attribute values must be enclosed in “” or ‘’
Processing instructions are optional
XML is case-sensitive
<tag> and <TAG> are not the same type of element

82. Comp Sci 346
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83. Comp Sci 346
12/28/2017