Slide 1
INTRODUCTION TO XML Underlying Technologies XML Is the
GlueProgram the WebXMLBrowse the WebHTMLTCP/IPConnect the
WebTechnologyInnovationConnectivityPresentationConnecting
ApplicationsFTP, E-mail, GopherWeb PagesWeb ServicesIntroducing
XMLXML = Extensible Markup LanguageIn information technology,
extensible describes something, such as a program, programming
language, or protocol, that is designed so that users or developers
can expand or add to its capabilitiesBecause XML is extensible, it
can be used to create a wide variety of document types.XML enables
document authors to create entirely new markup languages for
describing specific types of data, including mathematical formulas,
chemical molecular structures, music, recipes, etc.
Markup is a text-based notation for describing data Some
XML-based markup languages include XHTML ,MathML (for mathematics),
VoiceXML (for speech), SMIL (the Synchronous Multimedia Integration
Languagefor multimedia presentations), CML (Chemical Markup
Languagefor chemistry) and XBRL (Extensible Business Reporting
Languagefor financial data exchange
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5
6
7 Welcome to XML!
8
Line numbers are not part of XML document. We include them for
clarity.Document begins with declaration that specifies XML version
1.0Element message is child element of root element myMessage XML
documents contain text that represents content (i.e. data) such as
welcome to xml !!It contains element that specify the documents
structure , such as mymessageXML documents delimit elements with
start tags and end tags Start tag the element name in angle
brackets End tag consists of the element name preceded by a forward
slash (/) Every XML document must have exactly one root element
that contains all the other elements such as mymessageVIEWING AND
MODIFIFYING XML documents XML documents are highly portable.
Viewing or modifying an XML documentwhich typically ends with the
.xml filename extensiondoes not require special software. Any text
editor that supports ASCII/Unicode characters can open XML
documents for viewing and editing. One important characteristic of
XML is that it is both human readable and machine
readable.Processing XML documentsProcessing an XML document
requires a software program called an XML parser (or an XML
processor)Parsers check an XML documents syntax and enable software
programs to process marked-up dataXML syntax requires: a single
root element , a start tag, and an end tag for each element
properly nested tags (i.e. the end tag for a nested element must
appear before the end tag of the enclosing element)
XML is case sensitive .A document that conforms to this syntax
is a well-formed XML document and is syntactically correct.Parser
is built in IE7 and FF2Validating XML DocumentsAn XML document
optionally can reference a document that defines that XML documents
structure. This document is either a Document Type Definition (DTD)
or a schema.When an XML document references a DTD or schema, some
parsers (called validating parsers) can read the DTD/schema and
check that the XML document follows the structure that the
DTD/schema defines. If the XML document conforms to the DTD/schema
(i.e., the document has the appropriate structure), the XML
document is valid. Parsers that cannot check for document
conformity against DTDs/schemas are non-validating parsers. If an
XML parser (validating or non-validating) can process an XML
document successfully, that XML document is well formed (i.e., it
is syntactically correct). By definition, a valid XML document also
is well-formed.
Elements title, date, author, summary and content are child
elements of article.1 2 3 4 5 6 7 8 Simple XML9 10 September 19,
200111 12 13 Tem14 Nieto15 16 17 XML is pretty easy.18 19 Once you
have mastered XHTML, XML is easily20 learned. You must remember
that XML is not for21 displaying information but for managing
information.22 23 24 Optional XML declaration.Element article is
the root element.IE713We begin with the optional XML declaration on
line 1. Value version indicates the XML version to which the
document conforms. The current XML standard is version 1.0.Blank
lines (line 2), white spaces and indentation help improve
readability Comments (lines 3-4) begin with , can be placed
anywherePlacing any characters including white spaces before the
XML declaration is an errorLine2(1-4) is the XML prologlines(6-24)
are the root element XML element and attribute names can be of any
length and may contain letters, digits, underscores, hyphens and
periods. However, XML names must begin with either a letter or an
underscore.Using either a space or a tab in an XML element or
attribute name is an error using xml in any combination of
uppercase or lower case letter at the beginning is error
Parent(container)/ child relationship (all children at the same
nesting level are siblings)
Viewing an xml DocumentNote that the XML document is simply a
text file does not contain formatting information for the article.
This is because XML is a technology only for structuring data.
Formatting and displaying data from an XML document are application
specific issues. For example, when Internet Explorer 7 loads an XML
document, IE7s parser msxml (Microsoft XML Core Services) parses
and displays the document data .the firefox has a similar
capability .Each browser has a built-in style sheet to format the
data
Firefox18Notice the minus sign () and plus sign (+). IE7 places
these symbols next to all container elements. A minus sign
indicates that IE7 is displaying that container elements child
elements. Clicking the minus sign next to an element causes IE7 to
hide that container elements children and replaces the minus sign
with a plus sign. Clicking the plus sign next to an element causes
IE7 to display that container elements children and replaces the
plus sign with a minus sign.
The same can be found in FF2
Document Type DefinitionsA DTD enables an XML parser to verify
whether an XML document is valid (i.e., its elements contain the
proper attributes, are in the proper sequence, etc.)..XML Markup
for a Business letter
Jane Doe Box 12345 15 Any Ave. Othertown Otherstate 67890
555-4321
This xml document references a DTD John Doe 123 Main St. Anytown
Anystate 12345 555-1234
Dear Sir:
It is our privilege to inform you about our new database managed
with XML. This new system allows you to reduce the load on your
inventory list server by having the client machine perform the work
of sorting and filtering the data.
Please visit our website for availability and pricing.
Sincerely, Ms. Jane Doe
: root element line(7-43)
Root element letter contains child elements contact, salutation,
paragraph, closing and signature. ....
Element with attribute ( type = ) (sender)
NotesCase sensitive not
Attribute name Attribute value Jane DoeElement with data between
elements tags
letter.dtd 26
To reference the DTD file we use :
referenceRoot nameExternal file Name & locationWe have :
ELEMENTEMPTYATTLIST#RQUIREDCDATA#FIXED#IMPLIED#PCDATAELEMENT
element type declaration defines the rules for element letter. In
this case, letter contains one or more contact elements, one
salutation element, one or more paragraph elements, one closing
element and one signature element,in that sequence. The plus sign
(+) occurrence indicator specifies that the DTD allows one or more
occurrences of an element. asterisk (*), which indicates an
optional element that can occur any number of times (zero or
more)the question mark (?), which indicates an optional element
that can occur at most once (zero or one occurrence) If an element
does not have an occurrence indicator, the DTD allows exactly one
occurrence.The contact element definition (line 7) specifies that
element contact contains child elements name, address1, address2,
city, state, zip, phone and flag in that order. The DTD requires
exactly one occurrence of each element.ATTLISTelement type
declaration to define an attribute (i.e., type) for the contact
element.
KEYWORD #IMPLIEDspecifies that if the parser finds a contact
element without a type attribute, the parser can choose an
arbitrary value for the attribute or ignore the attribute and the
document will be valid.KEYWORD #REQUIREDspecifies that the
attribute must be present in the element, and keywordKEYWORD
#FIXED
specifies that the attribute (if present) must have the given
fixed value. For example,
indicates that attribute zip must have the value 01757 for the
document to be valid
KEYWORD# DEFAULT The attribute has a default valueCDATA
CDATA specifies that attribute type contains character data
(i.e.,a string) which indicates that the parser will not process
the data, but will pass the data to the application without
modification.
#PCDATA
specifies that the element can contain parsed character data
(i.e., text). Parsable character data should not contain markup
characters, such as less than () and ampersand (&). The
document author should replace any markup character with its
corresponding entity (i.e., or &).
Appendix A contains special characterEntity
ReferencesCharacter
Tove Jani Reminder Don't forget me this weekend
This XML document has a reference to a DTD:
Tove Jani Reminder Don't forget me this weekend!
A Reference to a DTD
A DTD File
Using xml Schema XML Schema is an XML-based alternative to
DTD.An XML schema describes the structure of an XML document.The
XML Schema language is also referred to as XML Schema Definition
(XSD).
An XML SCHEMA The purpose of an XML Schema is to define the
legal building blocks of an XML document, just like a DTD.An XML
Schema:defines elements that can appear in a documentdefines
attributes that can appear in a documentdefines which elements are
child elementsdefines the order of child elements
What is an XML Schema?
defines the number of child elementsdefines whether an element
is empty or can include textdefines data types for elements and
attributesdefines default and fixed values for elements and
attributes
We think that very soon XML Schemas will be used in most Web
applications as a replacement for DTDs. Here are some reasons:XML
Schemas are extensible to future additionsXML Schemas are richer
and more powerful than DTDsXML Schemas are written in XMLXML
Schemas support data typesXML Schemas support namespacesXML Schemas
are much more powerful than DTDs.
XML Schemas are the Successors of DTDs
Tove Jani Reminder Don't forget me this weekend!
A Simple XML Document
An XML Schema
Tove Jani Reminder Don't forget me this weekend!
A Reference to an XML Schema
The element is the root element of every XML Schema:
......
The Element
The element may contain some attributes. A schema declaration
often looks something like this:
......
xmlns:xs=http://www.w3.org/2001/XMLSchema
indicates that the elements and data types used in the schema
come from the "http://www.w3.org/2001/XMLSchema" namespace. It also
specifies that the elements and data types that come from the
"http://www.w3.org/2001/XMLSchema" namespace should be prefixed
with xs:
targetNamespace=http://www.w3schools.com
indicates that the elements defined by this schema (note, to,
from, heading, body.) come from the "http://www.w3schools.com"
namespace.
xmlns=http://www.w3schools.com
indicates that the default namespace is
"http://www.w3schools.com".
elementFormDefault="qualified
indicates that any elements used by the XML instance document
which were declared in this schema must be namespace qualified.
Referencing a Schema in an XML Document
Example
noNamespaceSchemaLocation attribute is very similar to the
schemaLocation attribute, in that it allows you to specify the
location of a Schema for use with your document. However, since a
Schema is not required to have a targetNamespace, this attribute
can be used for Schema that do not have a namespace
xsi:noNamespaceSchemaLocation
This is family.xsd file in the same folder with xml file
Xml file :Example
No target spaceRoot element This is note.xsd file in the same
folder with xml file:
......
Example Xml file
Root elementTarget name space Hello From XML This is an XML
document! We can use also UTF-16 or ISO-8859-1
Character Encodings: The structures that make up an XML Schema
are called components, and every XML Schema is essentially a set of
components which outline the constraints placed on the content of
an XML document.
Documents which contain XML elements and attributes are XML
instance documents, and Schema can constrain those instancesThe
Components of XML SchemaSimple elements A simple element is an XML
element that can contain only text. It cannot contain any other
elements or attributes.However, the "only text" restriction is
quite misleading. The text can be of many different types. It can
be one of the types included in the XML Schema definition (boolean,
string, date, etc.), or it can be a custom type that you can define
yourself.You can also add restrictions (facets) to a data type in
order to limit its content, or you can require the data to match a
specific pattern.
A Simple Element
The syntax for defining a simple element is:
where xxx is the name of the element and yyy is the data type of
the element. XML Schema has a lot of built-in data types. The most
common types
are:xs:stringxs:decimalxs:integerxs:booleanxs:datexs:time
Defining a Simple Element
Here are some XML elements:Refsnes361970-03-27And here are the
corresponding simple element definitions:
