anchor.diff:    There is nothing specifically "Angular" about services. Angular itself has no definition of a "service". 
     There is no service base class, no place to register a "service".
     
  -  Yet services are fundamental to any Angular application. Our components are big consumers of service.
  +  Yet services are fundamental to any Angular application. Our components are big consumers of services.
   
     We prefer our component classes lean. Our components don't fetch data from the server, 
  -  they don't validate user input, they don't log directly to console. They delegate such task to services.
  +  they don't validate user input, they don't log directly to the console. They delegate such tasks to services.
     
     A component's job is to enable the user experience and nothing more. It mediates between the view (rendered by the template)
  -  and the application logic (which often includes some notion of a "model").  
  -  A good component presents properties and methods for data binding. 
  -  It delegates everything non-trivial to services.
  +  and the application logic (which often includes some notion of a "model").  A good component presents
  +  properties and methods for data binding. It delegates everything non-trivial to services.
   
     Angular doesn't *enforce* these principles. 
  -  It won't complain if write a "kitchen sink" component with 3000 lines.
  +  It won't complain if we write a "kitchen sink" component with 3000 lines.
     
     Angular does help us *follow* these principles ... by making it easy to factor our
     application logic into services and make those services available to components through *dependency injection*.
  
positive.code:   ## Data Binding
    Without a framework, we would be responsible for pushing data values into the HTML controls and turning user responses
    into actions and value updates. Writing such push/pull logic by hand is tedious, error-prone and a nightmare to
    read as the experienced jQuery programmer can attest  
  figure
    img(src="/resources/images/devguide/architecture/databinding.png" alt="Data Binding" style="width:220px; float:left; margin-left:-40px;margin-right:20px" )
  :marked
  
negative.code:   this `currency` pipe expression,
  <div style="margin-left:40px">
  code-example(language="javascript" linenumbers=".").
    price | currency:'USD':true
  </div>
  :marked
    >displays a price of "42.33" as `$42.33`.
  