json & xml by mathura shreedher sridhar. xml introduction xml stands for “extensible markup...

JSON & XML

BYMathura Shreedher Sridhar

Introduction

• XML stands for “Extensible Markup Language”.• XML provides set of rules for encoding

documents.• XML is a general approach to represent all

types of information such as data sets, spread sheets, graphic displays etc.,

• XML provides the basic, common and simple structure or syntax to describe new formats.

Introduction

• XML was designed to describe the data.• XML was not designed to display the data but

HTML is.• XML is software and hardware independent

tool for carrying information.

XML Specifications

• The first version XML 1.0 was initially defined in 1998.

• The current 5th edition of XML 1.0 was published on November 26, 2008.

• The next version XML 1.1 was published on February 4, 2004.

• It’s current 2nd edition was published on August 16, 2006.

History

• XML is derived from SGML (Standard Generalized Markup Language).

• SGML’s utility to www was recognized in the early 1980’s and SGML was included in W3C’s list of activities.

• XML was compiled by a group of 11 members supported by 150-member interest group.

History

• XML working group communicated virtually and the design was accomplished by the combination of email and weekly conferences.

• First working draft of XML was published in 1996.

• XML 1.0 became a W3C recommendation on February 10, 1998.

History

• The other names proposed to XML were MAGMA (Minimal Architecture for Generalized Markup Applications), SLIM (Structured Language for Internet Markup) and MGML (Minimal Generalized Markup Language).

Key Constructs in XML

• Character: XML document is a string of characters. All Unicode characters can appear in XML.

• Processor and Application: The processor otherwise called XML Parser analyzes the markup and passes the structured information to an application.


• Markup and Content: markups begin with “<“ and end with “>” or begin with “&” and end with “;”. In CDATA section the delimiters <![CDATA[ and ]]> are markup. Whitespace before and after outermost element is classified as markup. The text between the markup is classified as content.

• Tag: markup construct that begins with “<“ and ends with “>”.


Tags are of 3 types: - start tag =>Ex:<section> - end tag => Ex: </section> - empty tag => <line-break/>• Elements: A logical document component with

start tag and end tag or empty tag. The text between start tag and end tag is called content. Ex: <author>Joe</author>


• XML Declaration: XML documents may begin by declaring some information about themselves as below<?xml version="1.0" encoding="UTF-8"?>

Additional Info

• XML tags are not predefined. You should define your own tags.

• XML tags can consist of international characters.

• XML is just a piece of information wrapped in tags.

• XML supports data sharing by storing the data in plain text format.

XML document structure

• XML document forms a tree structure that start at root and branches to leaves.

Example:<?xml version="1.0" encoding="UTF-8"?>

<note> <to>Tom</to> <from>Harry</from> <heading>Hi</heading> <body>Hello to Tom!</body></note>

XML document structure

• Root element => note.• 4 child elements => to, from, heading , body.

Entity References

• Some characters like <, > have special meaning in XML. If they are placed inside an XML element the XML parser will throw an error. For example

<message> 5 > 3 </message> will generate an error. To avoid this error replace “>” in XML content with entity reference.

Entity References

• There are 5 pre-defined entity references in XML.

Entity Reference Symbol Description

< < Less than

> > Greater than

& & Ampersand

' ‘ Apostrophe

" “ Quotation mark

XML Syntax Rules

• All elements must have a closing tag.• XML tags are case sensitive.• Tag names cannot contain special characters like

space, !"#$ etc. It cannot start with -,. or numeric digit

• XML elements must be properly nested.• XML documents must have a root element.• XML attribute values must be quoted.• Entity references are properly used.

XML Syntax Rules

• The syntax for writing comments is  .

• Whitespace is not truncated in XML.• XML should contain only properly encoded

Unicode characters• XML document which satisfies all the above

mentioned syntax rules is called “well formed” xml.

XML Namespaces

• XML namespaces helps to avoid naming conflicts.

• Naming conflicts occur when trying to mix XML documents from different XML applications.

• Example follows: Courtesy: http://www.w3schools.com/xml

XML Namespaces

• XML1:This XML carries information about HTML table .

<table> <tr> <td>Apples</td> <td>Bananas</td> </tr>

</table>

XML Namespaces

• XML2: This XML carries information about a table (piece of furniture) <table>

<name>African Coffee Table</name> <width>80</width> <length>120</length>

</table>

• If these 2 XML fragments are mixed together, this will return in naming conflicts.

XML Namespaces

• Solve the name conflict using prefix.<h:table>

<h:tr> <h:td>Apples</h:td> <h:td>Bananas</h:td> </h:tr>

</h:table>

XML Namespaces

<f:table> <f:name>African Coffee Table</f:name> <f:width>80</f:width> <f:length>120</f:length>

</f:table>• Now there will be no conflicts as two table

names are different.

XML Namespaces

• Define namespace using xmlns attribute.• The namespace declaration has the following

syntax. xmlns:prefix="URI".

XML Namespaces• Ex: <root>

<h:table xmlns:h="http://www.w3.org/TR/html4/"> <h:tr> <h:td>Apples</h:td> <h:td>Bananas</h:td> </h:tr></h:table>

<f:table xmlns:f="http://www.w3schools.com/furniture"> <f:name>African Coffee Table</f:name> <f:width>80</f:width> <f:length>120</f:length></f:table>

</root>

Valid XML documents

• A valid XML document must be well formed.• A valid XML document must conform to a

document type.• A document type or document definition or

document schema is the set of rules that defines legal elements and attributes for XML documents.

Valid XML documents

• There are different types of document definitions:- Document Type Definition (DTD)

- XML Schema

XML DTD

• A valid XML document is a “well formed” document that conforms to the rules of DTD.

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE note SYSTEM "Note.dtd"><note><to>Tom</to><from>Harry</from><heading>Hi</heading><body>Hi to Tom!</body></note>

XML DTD

• The DOCTYPE declaration in the above code contains reference to external dtd file. The dtd file can give the structure of the XML document like this.

<!DOCTYPE note[<!ELEMENT note (to,from,heading,body)><!ELEMENT to (#PCDATA)><!ELEMENT from (#PCDATA)><!ELEMENT heading (#PCDATA)><!ELEMENT body (#PCDATA)>]>

XML DTD

• The “!DOCTYPE note” defines that the root of the xml document is note.

• Root element “note” contains 4 child elements : to, from, heading and body.

• 4 child elements are of type “#PCDATA”.• #PCDATA means parseable text data.

XML Schema

• XML schema is XML-based grammar declaration and gives the structure of an XML document.

• An XML document that follows the syntax rules and validated against XML Schema is “Well Formed” and “Valid”.

XML Schema Example

<xs:schema version=“1.0” xmlns:xs=http://www.w3.org/2001/XMLSchema><xs:complexType name=“customer”><xs:sequence><xs:element name=“email” type=“xs:string” minOccurs=“0”/><xs:element name=“phoneNumber” type=“xs:string”minOccurs=“0”/>

http://www.w3.org/2001/XMLSchema

XML Schema Example

</xs:sequence><xs:attribute name=“first_name” type=“xs:string”/><xs:attribute name=“last_name” type=“xs:string”/></xs:complexType></xs:schema>

XML Schema Elements and Attributes

• schema – root element of every XML Schema. Contains attributes such as schema version.

• xmlns – xml namespace. Each element in the schema has default prefix xs which is associated with xmlns.

• element – xml schema element.• type – an element can be of any simple type

such as string, long, double.


• minOccurs, maxOccurs – Define the minimum and maximum occurrence of a type. This value may be a positive integer or term unbounded to indicate there is no maximum number of occurences.

• complexType – complexType can contain elements, subelements and attributes. A complexType can contain another complexType.


• sequence – An element may include other elements called child elements. The sequence element specifies that child element must appear in sequence.

• attribute – a complexType can have one or more attributes.

• choice – Used to indicate only one set of elements can be present in the containing element.

XML Parser

• XML Parser is a software library or package that provides interface methods to the client to work with XML documents.

• XML Parser checks the “well formed”ness of XML document.

• XML Parser validates the XML document using XML schema or DTD.

XML Parser

In this presentation 2 general parsers will be discussed:• DOM Parser• SAX Parser

DOM Parser

• DOM stands for Document Object Model• DOM Parser consists of DOM document object

which contains all the information about XML document.

• DOM Parser provides tree structure of an object

DOM Parser

<?xml version="1.0"?> <?xml-stylesheet type="text/css" href=“test.css"?>  <!DOCTYPE shapes SYSTEM “shapes.dtd"> <shapes> …… <square color=“BLUE”> <length> 20 </length> </square> …… </shapes>

DOM Parser

DOM Parser

• DOM Parser creates an internal structure like the above in memory which is DOM document object.

• Information about the XML document can be retrieved by invoking methods on this document object.

• DOM Parsers store the document object in memory.

SAX Parser

• SAX stands for Simple API for XML.• SAX is an event based sequential access parser

API.• The SAX event includes: XML Text nodes, XML

Elements Starts and Ends, XML Processing instructions and XML Comments.

• The user defines a number of callback methods that will be called when events occur during parsing

SAX Parser

• SAX is the fastest XML parsing method and is suitable for handling large documents that could not be read into memory all at once.

How XML can be used?

• Separate data from HTML using XML. Store data in XML file and use HTML only to display data. Any change in the data will not affect HTML file.

• Use XML for data transport between different systems over internet. XML data can be read by different incompatible applications.

• XML is plain text. Hence it is easy to store in software and hardware independent way.

Applications of XML

• Several document formats have been developed using XML. Eg: RSS, Atom, SOAP and XHTML.

• XML-based formats have become the default of many office productivity tools such as MS-Office, OpenOffice.org.

• XML has been employed as the base language of many communication protocols such as XMPP.

Applications of XML

• Configuration files for Microsoft .Net framework was done using XML.

• Apple has an implementation of a registry (property list files) based on XML.

• XML has been used as common interchange format in internet.

Introduction

• JSON stands for JavaScript Object Notation.• JSON is a text-based open standard format or

syntax used for storing and exchanging data.• It is primarily used to transmit data between

server and web application.• It is designed to be easier to use alternative to

XML.

Introduction

• JSON is derived from Javascript language. No extra software is needed to work with JSON in Javascript.

• It is language independent and can be implemented with most of the modern programming languages.

• JSON transmits objects in the form of attribute:value pairs.

• JSON is currently described by 2 competing standards RFC 7159 and ECMA – 404.

Introduction

• The internet media type for JSON is application/json.

• The JSON file extension is .json .

History

• The term JSON was coined by Douglas Crockford at his company State Software Inc founded in 2001 along with 5 of his colleagues.

• The JSON.org website was launched in 2002.• Yahoo started using JSON at it’s web services in

2005.• In 2006, Google started JSON in it’s Gdata web

protocol.

JSON specification

• JSON has no version number.• Since JSON is very stable, no revisions to the

JSON grammar are anticipated.

Basic Data types

• Number – signed number both integer and floating point. Does not allow NaN.

• String – sequence of zero or more Unicode characters enclosed with in double quotes.

• Boolean – true or false values.

Basic Data types

• Object – name/value pairs. Object are delimited with curly braces, commas are used to separate each name/value pair and with in each pair “:” separates name or key from value.

• Null – an empty value, using the word null.• Array – Ordered list of zero or more values.

Use [] notation with comma to separate elements.

Additional Info

• JSON supports four whitespace characters: the space, horizontal tab, line feed and carriage return.

• JSON ignores whitespace around syntactic elements

• JSON does not provide or allow any comment syntax.

• JSON does not support native data types such as Date, Error, Regular Expression and Function.

JSON representation example

Example Courtesy: http://en.wikipedia.org/wiki/JSON

var person = {“firstName”:”John”,“lastName”:”Smith”,“isAlive”:true,“age”:25,“height”:167.6,


“address”:{“streetAddress”:”21 XYZ Street”, “city”:”New York”,“state”:”NY”,“postalCode”:”10021-0031”

},


“phoneNumbers”:[{“type”:”home”,“number”:”222-222-2222”},{“type”:”office”,“number”:”333-333-3333”}],


“children”:[],“spouse”:null

}

JSON Methods

• JSON.parse()• JSON.stringify()

JSON.parse(text)

• parse() method converts the string information passed to it as an object.

• Demo courtesy: http://www.w3schools.com/json/

http://www.w3schools.com/json/

JSON.stringify(object)

• stringify() converts JSON object into string.• Demo courtesy:



Using Javascript in JSON

• Javascript function eval() is used to parse JSON data.

• Older browsers without the support for JSON.parse() use eval() function.

• eval() does the same job as JSON.parse().

JSON Schema

• JSON schema specifies the structure of JSON data for validation, documentation, and interaction control.

• It provides contract for JSON data required by any application.

• JSON schema is JSON based and is built on similar principles as XML Schema Definition (XSD).

JSON Schema Example

Example Courtesy: http://en.wikipedia.org/wiki/JSON{

“$schema”: “http://json-schema.org/draft-03/schema#”“name”:”Product”“type”: “object”“Properties”:{

“id”:{

JSON Schema Example

“type”:”number”“description”:”Product identifier”“required”:true

},“name”:{

“type”: “string”“description”: “Name of the product”“required”: true

}}

JSON Schema Example

Below data can be validated with the above schema.

{id:1,Name:”Foo”

}

Applications of JSON

• JSON-RPC an RPC protocol built on JSON.• JSON is used in AJAX(client side web

development technique).• It is used to transmit data between server and

web application.

JSON in NoSQL DBs

• JSON is used in NoSQL DBs such as Elastic search, CouchDB, RavenDB, MarkLogic Server, JasDB, RaptorDB, EJDB, SDB, Riak, Scalien, Pincaster, RaptorDB, InfoGrid, ArangoDB and VaultDB.

• JSON’s name/value type of storage made it possible to be used as a storage format in NoSQL DBs.

Comparison between JSON & XMLXML JSON

Simplicity XML is a text-based format. JSON is a text-based format.

Self-describing XML data format is self-describing.

JSON data format is self-describing.

Extensibility XML supports both primitive data formats like number, string and complex data formats like class.

JSON supports only primitive data formats like number, string.

Interoperability XML’s support of complex data type like classes make it less interoperable.

JSON’s strict support of only primitive data type make it more interoperable.

Openness XML follows open standard JSON is open. It is simple and not subject to standardization struggles

Comparison between JSON & XMLXML JSON

Internationalization XML uses unicode characters.

JSON uses unicode characters.

Parser DOM, SAX parsers are used to parse XML

Parsed by a standard JavaScript function

Why JSON is gaining attention?

JSON is faster and easier than XML:With XML• First, fetch an XML document• Then, use XML DOM parser and loop through the

document• Retrieve values and store in a variableWith JSON• Fetch a JSON string• JSON.Parse the JSON string and start using the object

Questions ?

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