ABSTRACT The first service description format for the Web appeared in 2001.The second didn't arrive until 2007. In 2010 there were less than five known service description formats. As of this writing there are more than a dozen. We’re experience a “Cambrian explosion” of service description formats! BONUS: link to Mike's notes on the presentation http://g.mamund.com/follow-v-hold Why all these new formats? Is there something missing that each new type tries to fix? Or are these new formats just repeating the same patterns over and over? This paper 1) explores two main approaches to service description design (describing functionality and describing things), 2) reviews key shortcomings of existing approaches that lead to client applications tightly bound to a single service instance, 3) offers up a new set of measures for useful service description, and 4) introduces an alternative format that supports the key Web principle of follow your nose.

1. Follow Your Nose
vs.
Hold Your Nose
Mike Amundsen
@mamund
@layer7 @CAInc
Observations on the state of service description on the Web

2. The Paper

3. Observations

4. Observations
● The Web
● Service Descriptions
● Something Else

5. The Web

6. The Web

8. The Disney Dog Rule
"I have just met you and I love you!" - Dug

9. The Disney Dog Rule
"HyperText provides a single user-interface to many
large classes of stored information…"
- Berners-Lee / Cailliau, 1990

10. The Disney Dog Rule
"HyperText provides a single user-interface to many
large classes of stored information…"
- Berners-Lee / Cailliau, 1990

11. The Disney Dog Rule
"We propose the implementation of a simple scheme to
incorporate several different servers of
machine-stored information already available."
- Berners-Lee / Cailliau, 1990

12. The Disney Dog Rule
"We propose the implementation of a simple scheme to
incorporate several different servers of
machine-stored information already available."
- Berners-Lee / Cailliau, 1990

13. The Disney Dog Rule
"Squirrel!" - Dug

14. The Disney Dog Rule
"[A] web of nodes in which the user can browse at will."
- Berners-Lee / Cailliau, 1990

15. The Disney Dog Rule
"[A] web of nodes in which the user can browse at will."
- Berners-Lee / Cailliau, 1990

16. The Disney Dog Rule
"[A]bility for humans and crawlers to follow their noses ...
makes for a powerfully simple discovery heuristic"
- Ed Summers, 2008

17. The Disney Dog Rule
"[A]bility for humans and crawlers to follow their noses ...
makes for a powerfully simple discovery heuristic"
- Ed Summers, 2008

18. Linking

19. Linking

20. Linking
"[Links are] necessary to connect the data we have into a
web, a serious, unbounded web in which one can find all
kinds of things." - Tim Berners-Lee, 2006-09

21. Linking
"[Links are] necessary to connect the data we have into a
web, a serious, unbounded web in which one can find all
kinds of things." - Tim Berners-Lee, 2006-09

22. Linking

23. Linking

24. Linking

25. The Web
● I love you
● Squirrel
● Power Law

26. Service Descriptions

27. Interface Description Language (IDL)

28. Legacy IDLs

29. Web IDLs

30. Web IDLs

31. On the Web...
"The interfaces are defined by the data
formats and protocols..."
- Tim Berners-Lee 1998

32. Web IDLs
Rarely support multiple formats and almost
always use only HTTP.

33. On the Web...
"[A] web of nodes rather than a hierarchical
tree is the basic concept behind HyperText."
- Berners-Lee/Cailliau, 1990

34. Web IDLs
Almost all Web IDLs define a hierarchy of
resources (nodes).

35. On the Web...
"[O]ne can go from one concept to
another..."
- Berners-Lee/Cailliau, 1990

36. Web IDLs
Clients are led to accept only the pre-
defined links from just one service.

37. Service Description

38. Service Description

39. The Web

40. But there may be something else...

41. Something Else

42. Something Else

43. Something Else

45. The Solution

46. The Problem

47. Modeling the problem domain

48. The Solution

49. Serendipity
"Web architecture is all about serendipity."
- Stu Charlton, 2007

50. So let's do this...

51. Describe the domain without
specifying format or protocol...

52. Allow clients and servers to
negotiate format and protocols

53. Describe the domain as a set of
nodes, not a hierarchy.

54. Allow clients and servers to
establish their own workflows

55. Describe the domain as
a scale-free network.

56. Encourage clients and servers to
link however they wish.

57. Something Else
● Open formats and protocols (I love you…)
● Nodes, not hierarchies (Squirrel!)
● Open linking for apps (Power Law)

58. Application-Level Profile Semantics

59. Application-Level Profile Semantics

60. Application-Level Profile Semantics

61. Application-Level Profile Semantics
"I have just met you and I love you!" - Dug

62. Application-Level Profile Semantics

63. Application-Level Profile Semantics
"Squirrel!" - Dug

64. Application-Level Profile Semantics

65. Application-Level Profile Semantics
"[Links are] necessary to connect the data we have into a
web, a serious, unbounded web in which one can find all
kinds of things." - Tim Berners-Lee, 2006-09

66. So what does this mean?

67. ALPS Specification Draft

68. If you build it...

69. Conclusions
● The Web is great
● Service Descriptions are not the Web
● ALPS describes problem domains for the Web

70. Let's build Linked Open Apps (LOA)

71. Follow Your Nose
vs.
Hold Your Nose
Mike Amundsen
@mamund
@layer7 @CAInc
Observations on the state of service description on the Web
http://g.mamund.com/follow-v-hold