Distribution and Publication with Atom Web Services (ZendCon 2008)

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 Distribution and Publication With Atom Web Services

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Hi, I’m Ben Ramsey. 2

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 3 Software Architect Organizer of Atlanta PHP user group Co-author of php|architect’s Zend PHP 5 Certiﬁcation Study Guide HTTP pedant and advocate of RESTful web applications

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Distribution 4

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services To deliver or pass out something 5

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Publication 6

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services To issue something for distribution 7

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 8 Distribution Publication

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 9 Content Store Web Service Clients

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 10 Content Store Web Service Clients

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Over a network, we’ll use HTTP for distribution and publication. 11

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Constrained interface Client-server Stateless Cacheable Layered 12

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services HTTP is RESTful. 13

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services What is REST? 14

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services “REST strictly refers to a collection of network architecture principles which outline how resources are defined and addressed.” — Wikipedia 15

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ What is REST? Representational State Transfer Not an architecture or a standard for developing web services Not a particular format or pattern It is a set of design principles 16

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Principles of REST Application state and functionality abstracted into resources Resources are uniquely addressable Resources share a uniform interface for transfer of state: Constrained set of operations Constrained set of content types 17

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Principles of REST A protocol that is: Client-server Stateless Cacheable Layered 18

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services A resource-oriented architecture is RESTful. 19

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Resource-oriented architecture Resources Their names (addresses) Their representations The links between them 20

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services “A resource can be anything that has identity. Familiar examples include an electronic document, an image, a service (e.g., ‘today’s weather report for Los Angeles’), and a collection of other resources. Not all resources are network ‘retrievable’; e.g., human beings, corporations, and bound books in a library can also be considered resources.” — RFC 2396 21

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ ROA basics Each resource knows how to do three simple things: 1. Represent itself to the client 2. Transition from one state to the next 3. Destroy itself Additionally, the ROA provides a means to create a resource 22

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ ROA properties Resources are addressable Resources have no state Resources are connected Resources share the same interface 23

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services This is REST in a nutshell. 24

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services What is Atom? 25

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services “The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (short AtomPub or APP) is a simple HTTP-based protocol for creating and updating web resources.” — Wikipedia 26

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Atom is both a format and a protocol. 27

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ The Atom format An XML-based web content and metadata syndication format Defined by RFC 4287 Developed as an open alternative to the “frozen” RSS 2.0 format XML namespace: http://www.w3.org/2005/Atom 28

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ The Atom Publishing Protocol An application-level protocol for publishing and editing web resources using HTTP and XML Defined by RFC 5023 Also called “AtomPub” or “APP” XML namespace: http://www.w3.org/2007/app 29

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ A common format Widespread adoption means increased interoperability between disparate systems Applications now have a common language and publishing protocol, leveraging HTTP as a vehicle Supported by a diverse and wide-reaching community through libraries for consuming and creating Atom services 30

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Principles of Atom Resource-oriented Discovery of resource relationships Categorization of resources Provides service auto-discovery Support for all content types Content can be published 31

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom is resource-oriented Think of an Atom web service as a catalog of resources that you want to expose Each piece of content in your system is a resource Each resource has a unique identifier The resources have no state They are cacheable They are connected They share the same interface: HTTP verbs 32

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom exposes relationships Atom documents are connected through links Links can have defined relationships: alternate related self enclosure via 33

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom categorizes resources Atom documents may belong to multiple categories Categories belong to namespaces Categories are very flexible; up to implementor to decide how to use them APP category documents expose categories, optionally defining limitations 34

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom provides auto-discovery APP service documents expose the collections of an Atom web service Service documents provide flexible workspaces for the implementor to define May define endpoints for publication of resources, acceptable content types, and categories 35

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom delivers content Collection documents (feeds) deliver lists of resources Collection documents can be paginated to allow paging through content Entry documents deliver individual resources, describing relationships with other resources and providing links to follow to more content 36

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom publishes content Individual entries may be published to an Atom web service to add or update content Atom allows for the deletion or removal of content entries Atom is flexible enough to allow for whole collection documents to be published, perhaps creating or updating many resources at one time 37

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Distribution with Atom 38

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Atom terminology Entry Feed Collection Category Document Service Document 39

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Entry Represents an individual piece of content (post, article, page, image, video, document, etc.) Entries can be related to other entries or feeds This resource represents a specific resource (i.e. http://example.org/posts/1234) Content type: application/atom+xml;type=entry 40

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 41

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Feed Represents a collection of Atom entries Feeds can be related to other feeds or entries This resource represents a specific collection of resources (i.e. http:// example.org/posts) Atom collections are feeds Content type: application/atom+xml;type=feed 42

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 43

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Category Categories provide metadata to describe an Atom entry; Atom itself doesn’t define usage of categories Category documents describe the categories that are allowed in collections Content type: application/atomcat+xml 44

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 45

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Service A service discovery document that describes the locations and capabilities of collections Usually the entry point of the Atom web service Content type: application/atomsvc+xml 46

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services 47

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Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Distribution and Publication With Atom Web Services Publication with Atom 48

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Creating resources Client “discovers” the resource through which the Atom service accepts POST requests to create resources (defined by app:collection) Client sends resource in POST request: POST /archives HTTP/1.1 Client receives a 201 Created response in the event of a success 49

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Modifying resources Client requests a representation of the resource: GET /archives/1234 HTTP/1.1 Client modifies the resource and tells the service to update it: PUT /archives/1234 HTTP/1.1 Service responds with a 200 OK status to indicate success Client uses “edit” relation for this logic 50

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Removing resources Client sends a DELETE request to the sevice: DELETE /archives/1234 HTTP/1.1 Service responds with a 204 No Content status code to indicate success 51

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Authentication Atom does not provide or recommend an auth mechanism Early favorite of the Atom community was WSSE Consider the use of OAuth Send authentication info through HTTP headers on each request requiring authenticated access 52

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Encryption Atom does not provide for encryption Use SSL for all sensitive communication Atom Entry and Feed Documents can contain XML Digital Signatures Can be encrypted using XML Encryption 53

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Extending Atom Atom is XML; as such, it may be extended using other vocabularies (namespaces) Use other namespaces to convey other information e.g. OpenSearch e.g. Dublin Core 54

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Parsing Atom DOM, XMLReader, XMLWriter, SimpleXML Zend_Feed, PEAR::XML_Feed_Parser, phpatomlib Apache Abdera 55

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ Out-of-box Atom clients Fude - http://www.witha.jp/eXeries/software/ Atomic (Firefox plugin) - https://addons.mozilla.org/en-US/firefox/addon/3188 APP Test Client - http://bitworking.org/projects/apptestclient/ 56

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Distribution and Publication With Atom Web Services Ben Ramsey ■ ZendCon ■ 16 Sep 2008 ■ For more information... http://tools.ietf.org/html/rfc4287 http://tools.ietf.org/html/rfc5023 http://atomenabled.org/ My blog: http://benramsey.com/ 57