Re: [Guidelines] Proposed update to section 4.5 (now 5.5), Design ating Optional Behaviors

Attached is updated edit for 5.5, Designating Optional behaviors. I  
also plan to add an informative reference for the MTOM assertion  
since it is discussed in the example.

To highlight the changes of the good practices and how they relate to  
what we have, I list them here:
(1)

---

"Good practice a: Limit use of Optional Assertions

Assertion Authors should not use optional assertions for behaviors  
that must be present in compatible policy expressions."

---

Good practice a is newly called out but reflects what was stated in  
the original text. This is not included in the Microsoft/IBM list of  
best practices.

(2)
---
"Good practice b: Indicate use of  an Optional Assertion
When a given behavior may be optional, it must be possible for both  
message participants to determine that the assertion is selected by  
both parties, either out of band or as reflected by the message  
content."

---
Good practice b is a revision of what was previously listed as a good  
practice 10, but now is more closely aligned with the text in the  
section. The original wording was
"Optional Assertion Authors should explicitly state how the behavior  
that is enabled by the assertion would be engaged when they are  
designing their assertion, whether by specific headers or some other  
means. See also ."

(3)
---
"Good practice c:  Consider entire message exchange pattern when  
specifying Assertions that may be optional	
Assertion Authors should associate optional assertions with the  
appropriate endpoint and use the smallest possible granularity to  
limit the degree to which optionality applies."

---

Good practice c is newly called out but reflects what was stated in  
the original text. It is similar to  G16 but highlights the special  
concern for optional.

Unless I hear comment I will update the document Monday. Thanks for  
your earlier helpful comments Prasad.

regards, Frederick

Frederick Hirsch
Nokia