Introduction to AtomPub Web Services (IPC 2010)

Since 2003, the Atom format has been used as yet another feed format like RSS, but the Atom protocol opens the door to far more uses of Atom as both a means for distribution and publication. Ben Ramsey introduces the Atom format and protocol, explaining how these can form the foundation of any publishing service and serve as a platform for rich Internet applications.

Transcript

1. Ben Ramsey • International PHP Conference • 11 Oct 2010 Introduction to AtomPub Web Services
2. Introduction to AtomPub Web Services • Ben Ramsey Hi, I’m Ben. ‣VP of Engineering at Moontoast ‣Co-founder and organizer emeritus of the Atlanta PHP user group ‣Current organizer of the Nashville PHP user group ‣I blog at benramsey.com ‣I tweet at @ramsey ‣Please rate this presentation: http://joind.in/2185 2
3. Atom & AtomPub?

4. What’s the difference?

5. Introduction to AtomPub Web Services • Ben Ramsey Atom: RFC 4287 5
6. Atom is an XML-based document format that describes lists of related information known as “feeds”. Feeds are composed of a number of items, known as “entries”, each with an extensible set of attached metadata. For example, each entry has a title. The primary use case that Atom addresses is the syndication of Web content such as weblogs and news headlines to Web sites as well as directly to user agents.
   —RFC 4287, §1
7. Atom is an XML language.
8. Introduction to AtomPub Web Services • Ben Ramsey AtomPub: RFC 5023 8
9. The Atom Publishing Protocol is an application-level protocol for publishing and editing Web Resources using HTTP and XML 1.0. The protocol supports the creation of Web Resources and provides facilities for: Collections: Sets of Resources, which can be retrieved in whole or in part.
   Services: Discovery and description of Collections. Editing: Creating, editing, and deleting Resources. The Atom Publishing Protocol is different from many contemporary protocols in that the server is given wide latitude in processing requests from clients.
   —RFC 5023, §1
10. AtomPub is a
    publishing protocol.
11. Introduction to AtomPub Web Services • Ben Ramsey What about RSS? 11
12. Introduction to AtomPub Web Services • Ben Ramsey Content Types 12 ‣RSS allows only for plain text and escaped HTML content types ‣Atom provides for plain text, escaped HTML, XHTML, XML, and Base64-encoded binary data
13. Introduction to AtomPub Web Services • Ben Ramsey Internationalization ‣RSS may have a language set for a feed, but doesn’t have a way to indicate language for items in the feed ‣Atom uses the xml:lang attribute to specify language on a per-element basis ‣Atom uses IRIs, which allow the usage of characters in identifiers outside of ASCII 13
14. Introduction to AtomPub Web Services • Ben Ramsey Modularity ‣RSS vocabulary elements aren’t reusable in other XML vocabularies ‣Atom was designed to allow its vocabulary to be mixed with other XML vocabularies ‣Namespaces! Atom has one; RSS does not 14
15. Introduction to AtomPub Web Services • Ben Ramsey Other Things ‣RSS has no schema; Atom has a RelaxNG schema ‣RSS defines no mechanism for handling relative URIs; Atom uses xml:base ‣Various implementations in RSS leads to interoperability problems ‣No standard protocol for publishing; RSS is read only 15
16. Atom was created to solve the RSS problems.
17. Introduction to AtomPub Web Services • Ben Ramsey Profile of Atom ‣Atom Syndication Format ‣An XML-based web content and metadata syndication format ‣Defined by IETF RFC 4287 ‣Fixes the “problems” of RSS ‣XML namespace: http://www.w3.org/2005/Atom 17
18. Introduction to AtomPub Web Services • Ben Ramsey Profile of AtomPub ‣Atom Publishing Protocol or APP ‣A protocol for publishing and editing web resources using HTTP and XML ‣Defined by IETF RFC 5023 ‣Uses Atom as it’s XML syntax ‣XML namespace: http://www.w3.org/2007/app 18
19. Introduction to AtomPub Web Services • Ben Ramsey Basics of AtomPub ‣Each resource has a unique identifier ‣The resources are well-connected ‣Resources share the same interface ‣There is no state; requests are atomic ‣Follows a resource-oriented architecture 19
20. Introduction to AtomPub Web Services • Ben Ramsey Terminology ‣Entry ‣Feed/Collection ‣Category Document ‣Service Document 20
21. Introduction to AtomPub Web Services • Ben Ramsey Content Types ‣Entry: 
 application/atom+xml;type=entry ‣Feed/Collection:
 application/atom+xml ‣Category Document:
 application/atomcat+xml ‣Service Document:
 application/atomsvc+xml 21
22. Introduction to AtomPub Web Services • Ben Ramsey Designing an AtomPub Service 22
23. Introduction to AtomPub Web Services • Ben Ramsey What will our service do? 23 ‣Expose users ‣Expose content ‣Allow users to manipulate content
24. Step 1:
    Define our URIs
25. Introduction to AtomPub Web Services • Ben Ramsey Users ‣/user ‣/user/{username} ‣For example: /user/ramsey 25
26. Introduction to AtomPub Web Services • Ben Ramsey Content ‣/content ‣/content/{id} ‣For example: /content/1234 26
27. Step 2:
    Define the relationships
28. Introduction to AtomPub Web Services • Ben Ramsey Relationship Building ‣user ⇛ content:
 one to many ‣content ⇛ user:
 one to one 28
29. Step 3:
    Define the interface
30. Methods GET PUT POST DELETE Cut & Paste Copy Paste Over Paste After Cut
31. Introduction to AtomPub Web Services • Ben Ramsey Actions for User Resources ‣Retrieve user collection:
 GET /user ‣Create a new user:
 POST /user ‣Modify an existing user:
 PUT /user/ramsey ‣Delete a user:
 DELETE /user/ramsey 31
32. Introduction to AtomPub Web Services • Ben Ramsey Actions for Content Resources ‣Retrieve content:
 GET /content ‣Create new content:
 POST /content ‣Modify content:
 PUT /content/1234 ‣Remove content:
 DELETE /content/1234 32
33. Introduction to AtomPub Web Services • Ben Ramsey Other Actions ‣Service discovery:
 GET / ‣Retrieve content for a particular user:
 GET /user/ramsey/content 33
34. Introduction to AtomPub Web Services • Ben Ramsey Let’s see it in action 34
35. GET / HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 21 Sep 2009 16:33:45 GMT Content-Type: application/atomsvc+xml
36. <?xml version="1.0" encoding="utf-8"?> <service xmlns="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <workspace> <atom:title>Our Content Store</atom:title> <collection href="user"> <atom:title>Users</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/user"/> </collection> <collection href="content"> <atom:title>Content</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/content"/> </collection> </workspace> </service>
37. GET /user HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 21 Sep 2009 16:34:26 GMT Content-Type: application/atom+xml
38. <?xml version="1.0" encoding="utf-8"?> <feed xmlns="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xml:base="http://atom.example.org/"> <title>Users</title> <updated>2009-09-21T05:21:19Z</updated> <id>tag:example.org,2009-09:user</id> <app:collection href="user"> <title>Users</title> <app:accept>application/atom+xml;type=entry</app:accept> <app:categories href="cat/user"/> </app:collection> <link rel="first" href="user"/> <link rel="last" href="user?p=23"/> <link rel="next" href="user?p=2"/> <entry> ... </entry> </feed>
39. Introduction to AtomPub Web Services • Ben Ramsey Manipulating a User 39
40. GET /user/ramsey HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 21 Sep 2009 16:34:26 GMT Content-Type: application/atom+xml;type=entry
41. <?xml version="1.0" encoding="utf-8"?> <entry xmlns="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <title>ramsey</title> <author> <name>ramsey</name> </author> <link rel="self" href="user/ramsey"/> <link rel="edit" type="application/atom+xml;type=entry" href="user/ramsey"/> <link rel="related" href="user/ramsey/content"/> <id>tag:example.org,2008:user/ramsey</id> <updated>2009-09-21T13:45:00Z</updated> <published>2008-05-23T16:23:34Z</published> <content type="xhtml"> <div class="vcard" xmlns="http://www.w3.org/1999/xhtml"> <a class="fn">Ben Ramsey</a> <span class="tel">123-456-7890</span> </div> </content> </entry>
42. Introduction to AtomPub Web Services • Ben Ramsey Modify the Entry Locally 42
43. <?xml version="1.0" encoding="utf-8"?> <entry xmlns="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <title>ramsey</title> <author> <name>ramsey</name> </author> <link rel="self" href="user/ramsey"/> <link rel="edit" type="application/atom+xml;type=entry" href="user/ramsey"/> <link rel="related" href="user/ramsey/content"/> <id>tag:example.org,2008:user/ramsey</id> <updated>2009-09-22T09:14:58Z</updated> <published>2008-05-23T16:23:34Z</published> <content type="xhtml"> <div class="vcard"> <a class="fn url" href="http://benramsey.com/">Ben Ramsey</a> <span class="org">Moontoast</span> <span class="tel">123-456-7890</span> </div> </content> </entry>
44. PUT /user/ramsey HTTP/1.1 Host: atom.example.org Content-Type: application/atom+xml;type=entry {body here} HTTP/1.x 200 OK Date: Mon, 22 Sep 2009 09:14:59 GMT Content-Type: application/atom+xml;type=entry
45. Introduction to AtomPub Web Services • Ben Ramsey Add Some Content 45
46. Introduction to AtomPub Web Services • Ben Ramsey First, a Few Notes 46 ‣You need authentication! ‣Perhaps you need encryption ‣You definitely need validation ‣And I’m not going to tell you how
47. That’s out of scope.
48. :-)
49. But I’ll show you the basics.
50. <?xml version="1.0" encoding="utf-8"?> <service xmlns="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <workspace> <atom:title>Our Content Store</atom:title> <collection href="user"> <atom:title>Users</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/user"/> </collection> <collection href="content"> <atom:title>Content</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/content"/> </collection> </workspace> </service>
51. Introduction to AtomPub Web Services • Ben Ramsey Get the Categories 51
52. GET /cat/content HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 22 Sep 2009 09:39:26 GMT Content-Type: application/atomcat+xml
53. <?xml version="1.0"?> <app:categories xmlns:app="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" fixed="yes" scheme="http://atom.example.com/cat/content"> <atom:category term="audio"/> <atom:category term="video"/> <atom:category term="game"/> </app:categories>
54. Introduction to AtomPub Web Services • Ben Ramsey Create the Entry Document Locally 54
55. <?xml version="1.0" encoding="utf-8"?> <entry xmlns="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <title>Perfect</title> <author> <name>Mark Phelps</name> </author> <id>tag:example.org,2009:content/perfect</id> <published>2009-09-22T20:12:08Z</published> <category term="audio" scheme="http://atom.example.com/cat/content"/> <content type="application/mp4"> TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWF IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGl ... </content> </entry>
56. POST /content HTTP/1.1 Host: atom.example.org Content-Type: application/atom+xml;type=entry {body here} HTTP/1.x 202 Accepted Date: Mon, 22 Sep 2009 09:14:59 GMT {body contains status indicator}
57. Introduction to AtomPub Web Services • Ben Ramsey Authentication? ‣Atom doesn’t specify a preference ‣WSSE Username Token ‣OAuth ‣Basic authentication ‣Digest authentication ‣??? 57
58. Did I miss anything?
59. Oh, yeah.
    Where’s the PHP code?
60. Introduction to AtomPub Web Services • Ben Ramsey AtomPub in PHP ‣DOM for reading/writing ‣SimpleXML for reading ‣XMLReader for reading ‣XMLWriter for writing ‣String concatenation for writing ‣I recommend XMLReader/XMLWriter; they’re the fastest at parsing and generating XML 60
61. Introduction to AtomPub Web Services • Ben Ramsey Wrapping Up ‣You can extend Atom with other XML vocabularies (Dublin Core, etc.) ‣XML Digital Signature or XML Encryption may be used, or encrypt as a bag of bits ‣Use your preferred authentication method ‣Use HTTP in a RESTful fashion ‣Use DOM or XMLReader/XMLWriter to parse Atom documents 61
62. Introduction to AtomPub Web Services • Ben Ramsey Questions? ‣I blog at benramsey.com ‣I tweet at @ramsey ‣Please rate this presentation: http://joind.in/2185 ‣Read the Atom specifications:
 RFC 4287
 RFC 5023 ‣My company is Moontoast 62
63. Introduction to AtomPub Web Services Copyright © Ben Ramsey. Some rights reserved. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. For uses not covered under this license, please contact the author.
64. Introduction to AtomPub Web Services • Ben Ramsey Photo Credits 64 ‣Molecule display, by Christian Guthier ‣Atom, by jayneandd ‣Atomium - detail, by Constantin Barbu ‣Simplicity, by Subterranean Tourist Board ‣STEREO's Extreme UltraViolet Imager (EUVI), by NASA ‣Quantum Universe, by Gaurav ‣Fullerene Nanogears, by NASA ‣Little Atom, by Marrio ‣That Atom, by Albert O’Conner ‣Bokeh Spiral, by Eric Wüstenhagen ‣Chambered Nautilus Shell - detail, by Jitze Couperus