General

• I ensured all of our classes have the "Plc" prefix, as I did encounter situations in which very generic type names had collisions and I had to use the fully qualified class name (including the package name). The "Plc" prefix reduces this risk.
• This model is now simplified as it currently doesn't support reading of multi-values. There are multiple options to add Multi-Values, but I haven't decided on which option I like best:
  • Rename PlcRequest/ResponseItem to PlcSingleValueRequest/ResponseItem and add a Multi-Value counterpart, wich handles the multi-value.
  • Add a PlcMultiValueRequest/ResponseItem, which simply references multiple PlcRequest/ResponseItem objects and provides a "get(index)" method.
  • Add a getNumValues() (Not insisting on this name) method and give each of the accessors an "index" property (eventually additionally a no-args version which defaults to index 0) (I think I prefer this one but didn't want to blow up the class-diagram too much).

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PlcField (Aka Address)

• I Renamed Address to PlcQueryPlcField
• I still think there is no immediate need to define any fields or methods in this interface as I haven't seen any common ground yet. Even if we are currently adding "TYPE" information to most queriesfields, in Modbus the type is directly tied to the address you are reading. So If you are reading a "Register" or a "Coil", the datatype is fixed.

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• I removed the "getLister" method as I haven't seen any protocol or use-case where this actually made sense.

• I changed the "parseAddress" to "prepareQueryprepareField" as it sort of correlates to the "prepareStatement" of JDBC ... and some times I could imagine, that more work is involved than simple parsing of a string (For Beckhoff ADS and EtherNet/IP this method could actively connect to the corresponding resource so in future read operations only the connection-id has to be provided)

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