Subject: [cuss] Extensibility of Packages

From: Alan Johnston <[email-masked]>
Date: Fri, 13 Apr 2012 12:23:57 -0500

At IETF-83, there was discussion about how to handle extensions to
existing packages.

In particular, the concern was raised that if a new content or
encoding is defined for an existing package, this could cause UUI
failures to result.

The proposed solution was to not allow new content or encodings to be
defined for existing packages.  Instead, a new package would be
defined which would support the new content or encoding.

Here is some proposed new text.

The current text in draft-ietf-cuss-sip-uui-05 says:

OLD:

New "package" values MUST describe the new application which is
utilizing the UUI data and provide some use case examples.  The
default "content" value and other allowed contents MUST be defined or
referenced in another document for the package.

We propose the text say:

NEW:

New "purpose" values MUST describe the new application which is
utilizing the UUI data and provide some use case examples.  The
default "content" value and "encoding" value MUST be defined or
referenced in another document for the package.  Additional allowed
content and encodings MAY also be defined or referenced.

OLD:

New "encoding" values MUST reference a common encoding scheme or
define the exact new encoding scheme.

NEW:

New "encoding" values MUST reference a common encoding scheme or
define the exact new encoding scheme.  A previously defined UUI
encoding value can be used in a new package.  In this case, the usage
of the encoding is defined by that package.  New UUI encodings cannot
be added to existing packages - instead, a new package would need to
be defined.

OLD:

New "content" values MUST describe the content of the UUI data and
give some example use cases.  The default "encoding" and other allowed
encoding methods must be defined for this new content.  Note that a
content value can be used by multiple UUI packages.  In this case, the
semantics and usage of the content is defined by the package.

NEW:

New "content" values MUST describe the content of the UUI data and
give some example use cases.  A previously defined UUI content value
can be used in a new package.  In this case, the semantics and usage
of the content is defined by that package. New UUI content types
cannot be added to existing packages - instead, a new package would
need to be defined.

We would like to revise the draft in the next few days, so please send
any suggestions or corrections to the this proposed text to the list
as soon as possible.

- Alan -

---

From: "DRAGE, Keith (Keith)" <[email-masked]>
Date: Sat, 14 Apr 2012 02:29:17 +0200

The text is fine, however,

I cannot remember which section these appear in, but I would like to either put them, or repeat them, in a new section labeled "extensibility" or some such.

I'd also like to capture that extension can either be by defining a new replacement package, or by using the old one and a new one together. In the latter case, old implementations would default to using only the old package and could also indicate that using the feature tags.

Keith

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of
> Alan Johnston
> Sent: 13 April 2012 18:24
> To: [email-masked]
> Subject: [cuss] Extensibility of Packages
> 
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