anchor.diff:    
     The `HeroDetailComponent` is a *different* component than the `HeroListComponent` we've been reviewing.
     The `HeroDetailComponent` (code not shown) presents facts about a particular hero, the
  -  hero that the user selects from the list presented by the the `HeroListComponent`.
  -  The `HeroDetailComponent` is a **child** of the the `HeroListComponent`.
  +  hero that the user selects from the list presented by the `HeroListComponent`.
  +  The `HeroDetailComponent` is a **child** of the `HeroListComponent`.
   
   figure
     img(src="/resources/images/devguide/architecture/component-tree.png" alt="Metadata" align="left" style="width:300px; margin-left:-40px;margin-right:10px" )
  
positive.code:   Some modules are libraries of other modules.
    
    Angular itself ships as a collection of library modules called "barrels". 
    Each Angular library is actually a public facade over several logically related private modules.
    
    The `angular2/core` library is the primary Angular library module from which we get most of what we need.
    <br clear="all">
  
negative.code:   It modifies the behavior of an existing element (typically an `<input>`) 
    by setting its display value property and responding to change events.
    
    Angular ships with a few other directives that either alter the layout structure 
    (e.g. [ngSwitch](template-syntax.html#ngSwitch))
    or modify aspects of DOM elements and components 
    (e.g. [ngStyle](template-syntax.html#ngStyle) and [ngClass](template-syntax.html#ngClass)).
  