Changes to .7

[Aaron Hansen <ahansen@tridium.com>]

If you are an implementor and can't wait for .8 to be published, here 
are the important changes to .7 that we've made so far.

- Prototypes replaced by contracts, which are more like interfaces.
- Contracts are immutable.
- "proto" attribute is now "is".
- The "is" attribute is a list of uri's.
- Eliminate the resolution attribute on reals.
- Add displayVal attribute to all objects.
- Verbs have been replaced with operations.  The element is "op" and
  it has "in" and "out" attributes whose values are uri's.
- Inputs and outputs to operations that are void must return some type
  of object representing void/null.  Currently I use <obj null="true"/>
- Contract and operation in/out reads are implicitly verbose and
  infinitely deep.  I'm not sure if this is a spec item or a Tridium
  implementation detail.
- The only request option is verbose, the http query parameter is "v".
  - Non verbose attributes (always visible if not at default value)
    - name
    - val
    - displayVal
    - href
    - null
  - Verbose
    - <op> elements (in/out incl)
    - is
    - of
    - unit
    - displayName
    - icon
    - max
    - min
    - precision
    - range
    - writable
- The following are the subscription contracts:

<obj name="subscriptions" is="obix:Subscriptions">
  <op name="make" in="obix:Subscription" out="obix:Subscription"/>
</obj>

<obj href="obix:Subscription">
  <reltime name="lease"/>
  <op name="add"     in="obix:SubscriptionHrefs" 
out="obix:SubscriptionValues"/>
  <op name="remove"  in="obix:SubscriptionHrefs"/>
  <op name="poll"    out="obix:SubscriptionValues"/>
  <op name="refresh" out="obix:SubscriptionValues"/>
  <op name="delete"/>
</obj>

<obj href="obix:SubscriptionHrefs">
  <list name="hrefs" of="obix:Uri"/>
</obj>

<obj href="obix:SubscriptionValues">
  <list name="values" of="obix:Obj"/>
</obj>

Best,
Aaron Hansen
Tridium, Inc.