[Xml1-wire-devel] Tagging scenarios

[Sean K. <ke...@ad...>]

Folks:

To try to focus my thoughts on requirements, I'm trying
to come up with some actual scenarios where tagging
information is useful.  Here are a few basic ones
... what do you think?

Application: DS2406's arranged on a small bus in a
digital video server used to toggle control points in
diagnostic mode.

Software control needs to determine what DS2406 to
toggle based on what control point it's connected to.
It looks up in its storage that I/O board A's TP3 is
controlled by switch 12.00.01.1a.30.11.5f.  It
instructs the busmaster to match and toggle the switch.

The mapping here is from object-to-device.

Application: DS18S20's in long bus on arranged
throughout a building.

Software control performs an alarming device search,
and one DS18S20 appears.  It maps the device ID
10.00.00.5f.a3.20.6c to the thermometer in office
number 5 on level 3, and takes appropriate action.

The mapping here is from device-to-object.

In both cases, the tagging ties a device to a rather
unique object; a board identifier and test point in one
case, a room number and floor number in another.

Defining the metadata for these kinds of bindings won't
be easy since they're so application-specific.  I'm
almost tempted to say that tagging schema should be
completely generic instead.  Consider:

<!-- A bus consists of zero or more devices -->
<!ELEMENT bus (device*)>

<!-- A device has an ID and a maps to an object -->
<!ELEMENT device (id, object)>

<!-- A device has an attribute that indicates its type.
     This is redundant since the ID has the family code
     which also indicates the type. -->
<!ATTLIST device type (switch | thermometer | memory | serialNum |
dualSwitch) #REQUIRED)>

<!-- A device ID, the syntax is 8 hexadecimal numbers -->
<!ELEMENT id (#PCDATA)>

<!-- A serialized Java object, encoded in base-64 -->
<!ELEMENT object (#PCDATA)>

Giving documents that look like this:

<bus>
  <device type="switch">
    <id>12.00.01.1a.30.11.5f</id>
    <object>6ejoa*1had...</object>
  </device>
  <device type="switch">
    <id>12.00.01.29.35.08.cd</id>
    <object>koi=ijfe12...</object>
  </device>
  ...

In the alarming temperature case, mapping the device ID
to a serialized Java object is particularly powerful
because the object can be the thing responsible for
taking action on adjusting the temperature in that
particular room.  No other knowledge is needed in
tagging software.

But this doesn't solve the reverse mapping problem in
the first scenario.

Thoughts?

--Sean