Google Data Protocol Guy Mark Lifshitz. Motivation Google’s Mission: – Organize the world’s...

Google Data Protocol

Guy Mark Lifshitz

Motivation

• Google’s Mission:– Organize the world’s information– Make information universally accessible– Provide tools to access your information

• Avoid limitations on contexts:– Not limited to Google– Not limited to browsers

Foundation

• REST

• AtomPub • JSON• RSS

REST “Representational state transfer”

• Simple• Lightweight• Scalable• Maps well to representing and exposing data

• 1. Client sends a request to server• 2. Server process the request • 3. Server returns a response

AtomPub“Atom Publishing Protocol”

(RFC 5023)

AtomPub

• Originally created for blogs• Feed based• Feeds are found at a specific URI• An Atom Reader looks for entries in a feed

AtomPub

• Create

• Retrieve

• Update

• Delete

AtomPub

• Create– PUT

• Retrieve – GET

• Update– GET, modify feed, PUT

• Delete– DELETE

Calendar Atom Feed<?xml version="1.0" encoding="utf-8"?>

<id>http://www.google.com/calendar/feeds/default/settings</id>

<generator uri="http://www.google.com/calendar">Google Calendar</generator>

<title type="text">Coach's's personal settings</title>

<openSearch:startIndex>1</openSearch:startIndex>

<name>Coach</name>

<email>user@gmail.com</email>

</author>

<entry>

<id>http://www.google.com/calendar/feeds/default/settings/...</id>

<gCal:settingsProperty name="alternateCalendar" value="0"/>

</entry>

</feed>

<name>Coach</name>

</author>

<entry>

</entry>

</feed>

<name>Coach</name>

</author>

<entry>

</entry>

</feed>

<name>Coach</name>

</author>

<entry>

</entry>

</feed>

<name>Coach</name>

</author>

<entry>

</entry>

</feed>

<name>Coach</name>

</author>

<entry>

</entry>

</feed>

<name>Coach</name>

</author>

<entry>

</entry>

</feed>

JSON“JavaScript Object notation”

• Properties– Lightweight data interchange format– Widespread use among web developers– Easy to read and write– Can parse JSON using any language– JSON structures map directly to data structures

used in most programming languages• Within the Google Data Protocol, JSON objects

simply mirror the Atom representation.

JSON vs. XML• "firstName": "John",• "lastName": "Smith",• "age": 25,• "address": {• "streetAddress": "21 2nd Street",

"city": "New York",• "state": "NY",• "postalCode": "10021“• }, • "phoneNumbers": [• { "type": "home“, "number": "212 555-1234"},• { "type": "fax", "number": "646 555-4567" } • ],• "newSubscription": false,• "companyName": null

JSON vs. XML<Person firstName="John" lastName="Smith">

<streetAddress>21 2nd Street</streetAddress> <city>New York</city><state>NY</state> <postalCode>10021</postalCode>

</address> <phoneNumber type="home">555 1234</phoneNumber><phoneNumber type="fax">646 555-4567</phoneNumber><newSubscription>false</newSubscription> <companyName />

</Person>

Additional Features

• Authentication• Queries• Concurrency • Common Elements • Batch Processing

Authentication

• ClientLogin– Desktop applications– Uses text input in application

myService.setUserCredentials("jo@gmail.com", "mypassword");

• AuthSub– 3rd party websites – Directs you to Google’s website.

• Add query to the URL

• Basic:http://www.google.com/calendar/feeds/default/private/full

• Events before February 11th 2010, ordered by datehttp://www.google.com/calendar/feeds/default/private/full

?start-max=2010-02-11&orderby=starttime

• Use the API to build queries

CalendarQuery myQuery = new CalendarQuery(feedUrl);

myQuery.setMinimumStartTime(DateTime.parseDateTime("2006-03-16T00:00:00"));

myQuery.setMaximumStartTime(DateTime.parseDateTime("2006-03-24T23:59:59"));

CalendarEventFeed resultFeed = myService.query(myQuery, Feed.class);

Additional Features

• Authentication• Queries• Concurrency • Common Elements – “Kines”

• Batch Processing

Additional Features

Libraries

• Java• .NET• PHP• Python• JavaScript• Obj-C

API Library

• http://code.google.com/apis/gdata/

Examplepublic class CalendarTest {

public static void main(String[] args) { CalendarService myService = new CalendarService("exampleCo-exampleApp-1.0");myService.setUserCredentials("root@gmail.com", "pa$$word");

URL feedUrl = new URL("http://www.google.com/calendar/feeds/default/allcalendars/full");

CalendarFeed resultFeed = myService.getFeed(feedUrl, CalendarFeed.class);

System.out.println("Your calendars:");System.out.println();

for (int i = 0; i < resultFeed.getEntries().size(); i++) {CalendarEntry entry = resultFeed.getEntries().get(i); System.out.println("\t" + entry.getTitle().getPlainText());

Request

• GET PUT DELETEE HEAD POST– All Methods– POST not safe or idempotent

• Intermediaries can be added in between– Proxies and Gateways– Can add performance

Protocol

• Client Server• Stateless– Requests are independent (don’t know what other

interactions are doing)

• Layered – HTTP intermdiaries can be added without

changing behaviour

• Cacheable

• Architectural Style• Architecture of the web• HTTP (protocol)• Request Response. • Client requests from server, and server

responds.

Extends• Atom 1.0 • RSS 2.0 • Atom Publishing Protocol (APP).• Google Data protocol extends those standards in

various ways, using the extension mechanisms built into the standards.

• Feeds conform to either the Atom or RSS syndication formats.

• The publishing model conforms to the Atom Publishing Protocol.

AtomPub

• “Atom Publishing Protocol” (RFC 5023)

• Web syndication is an effective and popular method for providing and aggregating content.

• It also lets you send data to Google and update data that Google maintains.

Benefits

• Efficiency– Caches

• Scalability– Large set of origin servers

• Performance to user– Partial rendering of html and such.

Calendar Feed<feed xmlns="http://www.w3.org/2005/Atom" xmlns:openSearch="http://a9.com/-/spec/opensearch/1.1/" xmlns:gCal="http://schemas.google.com/gCal/2005" xmlns:gd="http://schemas.google.com/g/2005" gd:etag="W/"Ck8FQ3Y4cCp7I2A9WxVVEkU.""> <id>http://www.google.com/calendar/feeds/default/settings</id> <updated>2009-03-05T10:46:25.244Z</updated> <title type="text">Coach's's personal settings</title> <link rel="http://schemas.google.com/g/2005#feed" type="application/atom+xml" href="http://www.google.com/calendar/feeds/default/settings"/> <link rel="self" type="application/atom+xml" href="http://www.google.com/calendar/feeds/default/settings"/> <author> <name>Coach</name> <email>user@gmail.com</email> </author> <generator version="1.0" uri="http://www.google.com/calendar">Google Calendar</generator> <openSearch:startIndex>1</openSearch:startIndex> <entry> <id>http://www.google.com/calendar/feeds/default/settings/alternateCalendar</id> <updated>2009-03-05T10:46:25.245Z</updated> <link rel="self" type="application/atom+xml" href="http://www.google.com/calendar/feeds/default/settings/alternateCalendar"/> <gCal:settingsProperty name="alternateCalendar" value="0"/> </entry> <entry> <id>http://www.google.com/calendar/feeds/default/settings/country</id> <updated>2009-03-05T10:46:25.245Z</updated> <link rel="self" type="application/atom+xml" href="http://www.google.com/calendar/feeds/default/settings/country"/> <gCal:settingsProperty name="country" value="EH"/> </entry></feed>

Calendar Feed

<entry>

<id>http://www.google.com/calendar/feeds/default/settings/alternateCalendar</id>

<gCal:settingsProperty name="alternateCalendar” value="0"/>

</entry>

Atom Feeds <?xml version="1.0" encoding="utf-8"?>

<feed xmlns="http://www.w3.org/2005/Atom"><title>Example Feed</title><subtitle>A subtitle.</subtitle><link href="http://example.org/feed/" rel="self" /><link href="http://example.org/" /><id>urn:uuid:60a76c80-d399-11d9-b91C-0003939e0af6</id><updated>2003-1213T18:30:02Z</updated> <author>

<name>John Doe</name><email>johndoe@example.com</email>

</author> <entry>

<title>Atom-Powered Robots Run Amok</title><link href="http://example.org/2003/12/13/atom03" /> <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id> <updated>2003-12-13T18:30:02Z</updated> <summary>Some text.</summary>

</entry> </feed>

Atom Feeds<?xml version="1.0" encoding="utf-8"?>

</author> <entry>

</entry> </feed>

</author> <entry>

</entry> </feed>

</author> <entry>

</entry> </feed>

</author> <entry>

</entry> </feed>

</author> <entry>

</entry> </feed>

</author> <entry>

</entry> </feed>

Google Data Protocol Guy Mark Lifshitz. Motivation Google’s Mission: – Organize the world’s...

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