[salud] A better example -- comments sought

[[e-mail] (Dale R. Worley)]

The authors are discussing adding a section showing examples of use of
the extension features.  In that section is an example "Subsetting a
private extension URN".  That example is not very realistic (I can say
that because I wrote it myself), so I propose this replacement example:

    The company designated by "alfa.example.com(2013)" wants to define a
    set of URNs that specify the different ring patterns used by a
    "distinctive ring" service to alert for incoming calls that are
    directed to different directory numbers.  These ring patterns are
    composed of groups of ring sounds that have particular patterns of
    lengths.

    The company can create a private <alert-category>,
    "[e-mail]", and within it assign three 'alert'
    URNs that indicate the three different ring patterns used by the
    company's service:

	urn:alert:[e-mail]:long-long
	urn:alert:[e-mail]:short-long-short
	urn:alert:[e-mail]:short-short-long

    Later, the company designated by "bravo.example.com(2013)" wants to
    define an additional 'alert' URN for the ring pattern "short short",
    which it uses to support a fourth directory number for a phone
    instrument.  The company can create a <private-name> to be used with
    the "[e-mail]" <alert-category>:

	urn:alert:[e-mail]:[e-mail]

Comments?

Dale