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Data Flow Architecture (What is Data Flow Architecture? (Whole system as…

- - - - Simple division on sub-system
      - Sub-system can be stand-alone
    - - No interactive interface
      - No concurrency & low throughput
      - High latency
  - - - Similar:
        
        Independent modules
        
        Data connectors
      - Difference:
        
        Connectors are stream oriented
        
        Concurrent processing
    - - Data Source
      - Data Sink
      - Filter
        
        Independent data stream transformer:
        
        Reads data from input data stream
        
        Process data and write to output stream
        
        Does not wait for batched data as a whole
        
        Does not even have to know identity of i/o streams
        
        Classification
        
        Active Filter:
        
        pulls in data and push out the transformed data (pull/push)
        
        works with a passive pipe that provides read/write mechanisms for pulling and pushing.
        
        Example: UNIX pipe.
        
        Passive Filter:
        
        Lets connected pipe to push data in and pull data out.
        
        The filter must provide read/write mechanisms in this case.
      - Pipe
        
        Data conduit:
        
        Moves data from one filter to another
        
        Two types: character or byte streams
    - - Push only:
        
        A data source may push data in a downstream
        
        A filter may push data in a downstream
      - Pull only:
        
        A data sink may pull data from an upstream
        
        Filter may pull data from an upstream
      - Push/Pull:
        
        A filter may pull data from an upstream and push transformed data in a downstream.
    - - Advantages:
        
        High concurrency
        
        Reusability is easy – plug and play.
        
        Modifiability: Low due to coupling between filters
        
        Simplicity: Clear
        
        Flexibility: High, very modular design
        
        Lower latency
      - Disadvantages:
        
        Not suitable for dynamic interactions
        
        Data standards (ASCII, XML?)
        
        Overhead of data transformation among filters such as parsing is repeated in two consecutive filters
        
        Difficult to configure a P&F system dynamically.
        
        Error handling issue
  - - - Suitable for embedded System
      - Composed of:
        
        Sub-systems
        
        Connectors
      - Two types of sub-systems:
        
        executor processor unit
        
        controller unit
      - System depends on: Control Variables
    - - Controlled variable: target controlled variable
        
        E.g., Speed in a cruise control system
        
        E.g., Temperature in an auto H/A system.
      - Input variable: measured input data
      - Manipulated variable: can be adjusted by the controller
        
        E.g., motor rotation speed, etc.
    - - Embedded software system involving continuing actions
      - Needs to maintain an output data at a stable level.
      - The system has a set point which is the goal the system will reach and stay at that level
    - - Benefit
        
        Better for situations where no precise formula for deciding the manipulated variable
        
        Can be completely embedded
      - Limitations
        
        Requires more sensors to monitor system states