Rewrite of the overview section of the dev guide

docs/guide.overview.ngdoc

@@ -1,126 +1,153 @@
-@workInProgress
 @ngdoc overview
 @name Developer Guide: Overview
 @description
 
-# What is angular?
-Angular teaches your old browser new tricks. It is what HTML would have been if it had been
-designed for building web applications.
 
-Take a simple example of user input as shown below. If you were using just HTML and JavaScript to
-implement this form, you would need to define listeners, DOM updates, and complex input validators
-in order to update and format the result. In angular you can achieve the effect with zero lines
-of JavaScript code using a declarative approach. Click on the source tab of the example below to
-view the angular implementation of this form.
+* <a href="#H1_1">What Is Angular?</a>
+* <a href="#H1_3">The Angular Philosophy</a>
+* <a href="#H1_2">Anatomy Of An Angular App</a>
+* <a href="#H1_4">Why You Want Angular</a>
+* <a href="#H1_5">Angular's Ancestors</a>
+* <a href="#H1_6">Watch a Presentation About Angular</a>
+
+
+<a name="H1_1"></a>
+# What Is Angular?
+
+The short answer: angular is a new, powerful, client-side technology that makes it much easier for
+you to create dynamic web sites and complex web apps, all without leaving the comfort of your HTML
+/ JavaScript home.
+
+The long answer: it kind of depends on where you're coming from...
+
+* If you're a web designer, you might perceive angular to be a sweet   {@link guide.template
+templating} system, that doesn't get in your way and provides you with lots of nice built-ins that
+make it easier to do what you want to do.
+
+* If you're a web developer, you might be thrilled that angular functions as an excellent web
+framework, one that assists you all the way through the development cycle.
+
+* If you want to go deeper, you can immerse yourself in angular's extensible  HTML {@link
+guide.compiler compiler} that runs in your browser. This compiler teaches your browser new tricks.
+
+So then, angular's not just a templating system, but you can create fantastic templates with it;
+angular's not just a web framework, but it has a very nice one; and angular's not just an
+extensible HTML compiler, but it has one of those too.  Let's put it this way: angular includes
+these parts along with some others; it evolved naturally from earlier occurrences of these forms;
+and thus angular is something far greater than the sum of its parts. It sounds like... it's alive!
+
+## An Intro By Way of Example
+
+Let's say that you are a web designer, and you've spent many thous — erm, hundreds of hours
+designing web sites.  But at this point, the thought of doing DOM updates, writing listeners, and
+writing input validators, all to do something as simple as implementing a form!?  You either don't
+want to go there in the first place or you've been there and the thrill is gone.
+
+You could even be muttering to yourself as you hack another callback, "This is like building my own
+bike from scratch every time I want to ride to the store." But let's say a clever friend, who keeps
+tabs on these sorts of things, told you to check out angular.
+
+So now here you are checking out angular, and here is a simple example. Note that it features only
+the templating aspect of angular, but this should suffice for now to quickly demonstrates how much
+easier life can be with angular:
 
 <doc:example>
- <doc:source>
-  QTY: <input name="qty" value="1" ng:validate="integer:0" ng:required/>
-  *
-  Cost: <input name="cost" value="19.95" ng:validate="number" ng:required/>
-  =
-  {{qty * cost | currency}}
- </doc:source>
- <doc:scenario>
-  it('should show of angular binding', function(){
-    expect(binding('qty * cost')).toEqual('$19.95');
-    input('qty').enter('2');
-    input('cost').enter('5.00');
-    expect(binding('qty * cost')).toEqual('$10.00');
-  });
- </doc:scenario>
+<doc:source>
+ <h2>Bigg Bike Shop</h2>
+ <hr>
+ <b>Invoice:</b>
+ <br/>
+ <br/>
+ <table>
+  <tr><td> </td><td> </td>
+  <tr><td>Quantity</td><td>Cost</td></tr>
+  <tr>
+    <td><input name="qty" value="1" ng:validate="integer:0" ng:required/></td>
+    <td><input name="cost" value="199.95" ng:validate="number" ng:required/></td>
+  </tr>
+ </table>
+ <hr>
+ <b>Total:</b> {{qty * cost | currency}}
+ <hr>
+</doc:source>
+<!--
+<doc:scenario>
+ it('should show of angular binding', function(){
+   expect(binding('qty * cost')).toEqual('$19.95');
+   input('qty').enter('2');
+   input('cost').enter('5.00');
+   expect(binding('qty * cost')).toEqual('$10.00');
+ });
+</doc:scenario>
+-->
 </doc:example>
 
-Angular is to AJAX apps as Ruby on Rails is to round trip apps.
+Go ahead, try out the Live Preview above.  "Well I _declare_! It's a fully functioning form, with
+an instantly updating display, and input validation." Speaking of being declarative, let's walk
+through the example and look at the angular-related lines to see what's going on around here.
 
-# Angular frees you from:
- * **Registering callbacks:** Registering callbacks clutters your code, and it makes it hard to see
-   the forest from the trees. Removing common boilerplate code such as callbacks is advantageous
-   because it leaves the JavaScript with a more succinct version of your code, better describing
-   what your application does.
- * **Manipulating HTML DOM programatically:** Manipulating HTML DOM is a cornerstone of AJAX
-   applications, but it is very cumbersome and error-prone. By declaratively describing how the UI
-   should change as your application state changes, you are freed from low level DOM manipulation
-   activities. Most applications written with angular never have to programatically manipulate
-   the DOM.
- * **Marshaling data to and from the UI:** CRUD operations make up the majority of most AJAX
-   applications. The flow of marshaling data from the server to an internal object to a HTML form,
-   validating the form, displaying validation errors, returning to an internal model and then back
-   to the server creates a lot of boilerplate code. angular eliminates almost all of this
-   boilerplate. leaving code that is richer and describes the overall flow of the application
-   rather than implementation details.
- * **Writing tons of initialization code just to get started:** Typically you need to write a lot
-   of plumbing and initialization code just to get a basic "Hello World" AJAX app working. With
-   angular you can bootstrap your app easily using services, which are auto-injected into your
-   application in a GUICE-like dependency-injection style. This allows you to get started
-   developing features quickly. As a bonus, you get full control over the initialization process
-   in automated tests.
+In line __2__ of the example, we let the browswer know about the angular namespace:
+
+       2 <html xmlns:ng="http://angularjs.org">
+
+This ensures angular runs nicely in all major browsers.
+
+In line __3__ we do two angular setup tasks inside a `<script>` tag:
+
+1. We pull in `angular.js`.
+2. The angular {@link angular.directive.ng:autobind ng:autobind} directive tells angular to {@link
+guide.compiler compile} and manage the whole HTML document.
+
+       3 <script src="file:///Users/krculp/angular.js/build/angular.min.js" ng:autobind></script>
+
+Lines __14__ and __15__ set up one side of angular's very cool two-way data binding, as well as
+demonstrate some easy input validation:
+
+       14 Quantity: <input name="qty" value="1" ng:validate="integer:0" ng:required/>
+       15 Cost: <input name="cost" value="199.95" ng:validate="number" ng:required/>
+
+These input widgets look normal enough, but consider these points:
+
+* Remember the `ng:autobind` directive from line 3?  When this page loaded, angular bound the names
+of the input widgets (`qty` and `cost`) to variables of the same name.  Think of those variables as
+the "Model" part of the Model-View-Controller design pattern.
+* Note the angular directives, {@link angular.widget.@ng:validate ng:validate} and {@link
+ngular.widget.@ng:required ng:required}. You may have noticed that when you enter invalid data or
+leave the the input fields blank, the borders turn a plainly irritated red color, and the display
+value disappears.  These `ng:` directives make it easier to implement field validators than coding
+them in JavaScript, no?  Yes.
+
+And finally, the mysterious line #__19__:
+
+       19 Total: {{qty * cost | currency}}
+
+What's with the curly braces?  Those curly braces are your friend.  This notation, `{{ _expression_
+}}`, is a bit of built-in angular {@link angular.markup markup}, a shortcut that you use to display
+data. The expression within curly braces gets transformed by the angular compiler into an angular
+directive ({@link angular.directive.ng:bind ng:bind}).  The expression itself can be a combination
+of both an expression and a {@link angular.filter filter}: `{{ expression | filter }}`.
+
+In our example above, we're saying, "Bind the data we got from the input widgets to the display,
+multiply them together, and format the resulting number into something that looks like money."
 
 
-# angular is/has:
- * **An HTML Compiler:** angular is an HTML compiler in the browser. It allows you to give meaning
-   to any HTML element, attribute, or text and create new primitives as building blocks for your
-   application.
- * **Declarative:** Declarative means that you describe what the page looks like rather than
-   instructing how to draw the page. HTML is great at declaring static documents. Angular extends
-   the declarative nature of HTML beyond static documents to define dynamic applications.
- * **Declarative Templates:** In angular, you write HTML to declare the view and UI templates for
-   your application. You can express many common application constructs without using any
-   JavaScript at all.
- * **Bidirectional Data Binding:** Allows your application to have a single source of truth
-   (your model), where the HTML is a projection of the internal state of your application, which
-   you can provide to the user in a declarative way.
- * **Built-in Services:** angular provides many standard AJAX operations to get you going quickly,
-   and dependency-injection allows you to swap them out as needed. Common services include:
-   Dependency Inject, History Management, URL Router, AJAX/XHR requests, and data caching,
-   to name a few.
- * **Very testable:** Testing difficulty is dramatically affected by the way you structure your
-   code. With angular, testability is baked in.
+<a name="H1_3"></a>
+# The Angular Philosophy
 
-# angular is NOT a:
- * **Library:** You don't call its functions.
- * **Framework:** It does not call your functions.
- * **DOM Manipulation Library:** It does not provide a way to manipulate DOM, but does provide
-   primitives to create UI projections of your data.
- * **Widget Library:** There are lots of existing widget libraries that you can integrate with
-   angular.
+Angular is built around the belief that declarative code is better than imperative when it comes to
+building UIs and wiring software components together, while imperative code is clearly the way to
+go for expressing business logic.
 
-
-
-# Not just another templating system
-
-At the highest level, angular looks like a just another templating system, but there are few
-important reasons why angular is different and makes it a very good fit for application
-development.
-
-Angular:
- * **Uses HTML/CSS syntax:** This makes it easy to read and can be edited with existing HTML/CSS
-   authoring tools.
- * **Extends HTML vocabulary:** Angular allows you to create new HTML tags, which expand into
-   dynamic UI components.
- * **Executes in the browser:** Removes the round trip to the server for many operations and
-   creates instant feedback for users.
- * **Bidirectional data binding:** The model is the single source of truth. Programmatic changes
-   to the model are automatically reflected in the view. Any changes by the user to the view are
-   automatically reflected in the model.
- * **Services:** These allow for a reusable way of injecting dependencies into an application.
- * **MVC:** Clean separation between model-view-controller, which aids in understanding,
-   maintenance, and testing of large systems.
-
-
-# The angular philosophy
-
-Angular is built around the belief that declarative code is preferred over imperative when it
-comes to building UIs and connecting the pieces together.
-
-As an example, if you wanted to add a new label to your application, you could do so by simply
-adding text to the HTML template, saving the code, and refreshing your browser:
+Not to put too fine a point on it, but if you wanted to add a new label to your application, you
+could do it by simply adding text to the HTML template, saving the code, and refreshing your
+browser (this here is declarative):
 
 <pre>
 <span class="label">Hello</span>
 </pre>
 
-In programmatic systems you would have to write and run code like this:
+Or, as In programmatic systems (like {@link http://code.google.com/webtoolkit/ GWT}), you would
+have to write the code and then run the code like this:
 
 <pre>
 var label = new Label();
@@ -129,38 +156,182 @@ label.setClass('label');
 parent.addChild(label);
 </pre>
 
-## Benefits:
+That looks like, let's see, do some math, factor out the `<pre>`s, carry the one, ummm...  a little
+bit of markup versus four times as much code.
 
- * Compile-free: Change your template and logic code and reload the browser to see it run
-   immediately. In contrast, programmatic serverside views often need to be compiled and executed
-   to be viewed, which takes time. This dramatically increases the speed of your development cycle.
- * Declarative templates are easier to understand and change than programmatic instructions.
- * Declarative templates can be edited in existing HTML editors such as DreamWeaver, Eclipse,
-   TextMate, Vim, etc.
- * Declarative templates can be edited by web designers without the need to work with web
-   developers.
+More Angular Philosophy:
 
-HTML is missing certain features, which angular adds via its compiler, thereby "teaching" the
-browser these new tricks:
+* It is a very good idea to decouple DOM manipulation from app logic. This dramatically improves
+the testability of the code.
+* It is a really, _really_ good idea to regard app testing as equal in importance to app writing.
+Testing difficulty is dramatically affected by the way the code is structured.
+* It is an excellent idea to decouple the client side of an app from the server side.  This allows
+development work to progress in parallel, and allows for reuse of both sides.
+* It is very helpful indeed if the framework guides developers through the entire journey of
+building an app: from designing the UI, through writing the business logic, to testing.
+* It is always good to make common tasks trivial and difficult tasks possible.
 
- * Dynamic behavior
- * Componentizing HTML snippets into reusable components
- * Dynamically include other HTML templates
- * Two-way data binding
- * Rich validation in forms
- * Model-View-Controller modularization
+Now that we're homing in on what angular is, perhaps now would be a good time to list a few things
+what angular isn't:
 
-# Watch a presentation about angular
+* It's not a Library. You don't just call its functions, although it does provide you with some
+utility APIs.
+* It's not a DOM Manipulation Library. angular uses jQuery to manipulate the DOM behind the scenes,
+rather than give you functions to manipulate the DOM with yourself.
+* It's not a Widget Library. There are lots of existing widget libraries that you can integrate
+with angular.
+* It's not "Just Another Templating System". A part of angular is a templating system. The
+templating subsystem of angular is different from the traditional approach for these reasons:
+   * It Uses HTML/CSS syntax: This makes it easy to read and can be edited with existing HTML/CSS
+authoring tools.
+   * It Extends HTML vocabulary: Angular allows you to create new HTML tags, which expand into
+dynamic UI components.
+   * It Executes in the browser: Removes the round trip to the server for many operations and
+creates instant feedback for users as well as developers.
+   * It Has Bidirectional data binding: The model is the single source of truth. Programmatic
+changes to the model are automatically reflected in the view. Any changes by the user to the view
+are automatically reflected in the model.
+
+
+<a name="H1_2"></a>
+# Anatomy Of An Angular App
+
+This section describes the parts of an angular app in more detail.
+
+## Templates
+
+{@link guide.template Templates} are the part of angular that makes it easy and fun to create the
+UI for your web apps.  With angular's templates you can create a dynamic UI using only HTML and
+CSS, but now you can add your own elements, attributes, and markup.  The angular compiler reads the
+"angularized" HTML when your page loads, and follows the instructions in there to generate a
+dynamic page for you.  This is the View part of MVC. "But wait there's more": since the compiler is
+extensible, you can build your own declarative language on top of HTML!
+
+## Application Logic and Behavior
+
+Application Logic and Behavior, which you define in JavaScript, is the C in MVC. With angular you
+write the logic (the controllers) for your app, but because angular takes care of reflecting the
+state of the model in the view, you don't have to write listeners or DOM manipulators. This feature
+makes your application logic very easy to write, test, maintain, and understand.
+
+## Data
+
+In an angular app, all of your data is referenced from inside of a {@link angular.scope scope}.
+The scope is the data Model, the M in the MVC pattern. A scope is a JavaScript object that has
+watcher functions that keep tabs on the data that is referenced from that scope. The data could be
+one or more Javascript objects, arrays, or primitives, it doesn't matter.  What matters is that
+these are all referenced by the scope.
+
+This "scope thing" is how angular takes care of keeping your data model and your UI in sync.
+Whenever something occurs to change the state of the scope, angular immediately reflects that
+change in the UI, and vice versa.
+
+In addition to the three components described above (the MVC bits), angular comes with a set of
+{@link angular.service Services} that are very helpful for building web apps. The services include
+the following features:
+
+* You can extend and add application-specific behavior to services.
+* Services include Dependency-Injection, XHR, caching, URL routing, and browser abstraction.
+
+The following illustration shows the parts of an angular application and how they work together:
+
+<img class="left" src="img/angular_parts.png" border="0" />
+
+
+<a name="H1_4"></a>
+# Why You Want Angular
+
+Angular frees you from the following pain:
+
+* **Registering callbacks:** Registering callbacks clutters your code, making it hard to see the
+forest for the trees. Removing common boilerplate code such as callbacks is a good thing. It vastly
+reduces the amount of JavaScript coding _you_ have to do, and it makes it easier to see what your
+application does.
+* **Manipulating HTML DOM programatically:** Manipulating HTML DOM is a cornerstone of AJAX
+applications, but it's cumbersome and error-prone. By declaratively describing how the UI should
+change as your application state changes, you are freed from low level DOM manipulation tasks. Most
+applications written with angular never have to programatically manipulate the DOM, although you
+can if you want to, knock yourself out.
+* **Marshaling data to and from the UI:** CRUD operations make up the majority of AJAX
+applications. The flow of marshaling data from the server to an internal object to an HTML form,
+allowing users to modify the form, validating the form, displaying validation errors, returning to
+an internal model, and then back to the server (gah!) creates a lot of boilerplate code. Angular
+eliminates almost all of this boilerplate, leaving code that describes the overall flow of the
+application rather than all of the implementation details.
+* **Writing tons of initialization code just to get started:** Typically you need to write a lot of
+plumbing just to get a basic "Hello World" AJAX app working. With angular you can bootstrap your
+app easily using services, which are auto-injected into your application in a {@link
+http://code.google.com/p/google-guice/ Guice}-like dependency-injection style. This allows you to
+get started developing features quickly. As a bonus, you get full control over the initialization
+process in automated tests.
+
+
+<a name="H1_5"></a>
+# Angular's Ancestors
+
+Where does angular come from? What events led to the inevitability of the appearance of something
+like angular?
+
+## First There Was HTML
+
+HTML was initially designed long, long ago, in the great year of 1989, with the intention to create
+a markup language for sharing scientific documents over the network. Yes, yes, certainly there was
+SGML even before that, but it was so difficult that even esteemed scientists balked at using it.
+Thankfully, Tim Berners-Lee saved all of us from that pain with his much friendlier HTML.
+`<HTML><BODY>Thank You, TB-L!</BODY></HTML>`.
+
+## Then There Was JavaScript
+
+Fast forward to 1995: JavaScript was invented. This was done with the best of intentions!  But in
+practice it initially served mainly to annoy Internet users with cheap effects that "enhanced"
+static HTML documents.
+
+Fast forward to the mid 2000s, when a new breed of back-then-considered-rich web applications
+started to appear on the web. These were built with HTML, JavaScript, and CSS, and featured less
+annoying and more impressive effects. Can you recall the first time you saw apps like Gmail, or
+Google Maps, and you couldn't believe everything that was going on in the browser?
+
+## And JavaScript Prevailed
+
+As of this writing, in 2011, people are building still richer and more interactive web applications
+that often rival their desktop counterparts. And yet they are essentially still working with
+technology and programming primitives that were used decades ago for the creation of static
+documents with cheap graphic effects. At the same time, the web is HUGE now, and we
+can't just abandon the technologies it was built with. Applets, Flash and Silverlight tried it, and
+in some ways succeeded. Yet many would argue that in reality they failed, because they tried to
+work _around_ the web instead of working _with_ it.
+
+## And Then There Was Angular
+
+Angular recognizes the strengths of the existing "static" web technologies, as well as their
+deficiencies.  At the same time, angular is learning from the failures of other technologies that
+tried, or are trying, to work around the web.
+
+For these reasons angular plays to the strengths of established web technologies, instead of
+bypassing them. Angular sets out the goal of increasing the abstraction and programming primitives
+that developers use to build web applications, so as to better reflect the needs of modern web
+applications and their developers.
+
+
+<a name="H1_6"></a>
+# Watch a Presentation About Angular
+
+Here is an early presentation on angular, but note that substantial development has occurred since
+the talk was given in July of 2010.
 
 <object width="480" height="385">
-  <param name="movie" value="http://www.youtube.com/v/elvcgVSynRg&amp;hl=en_US&amp;fs=1"></param>
-  <param name="allowFullScreen" value="true"></param>
-  <param name="allowscriptaccess" value="always"></param>
-  <embed src="http://www.youtube.com/v/elvcgVSynRg&amp;hl=en_US&amp;fs=1"
-         type="application/x-shockwave-flash" allowscriptaccess="always"
-         allowfullscreen="true" width="480" height="385"></embed>
+ <param name="movie" value="http://www.youtube.com/v/elvcgVSynRg&amp;hl=en_US&amp;fs=1"></param>
+ <param name="allowFullScreen" value="true"></param>
+ <param name="allowscriptaccess" value="always"></param>
+ <embed src="http://www.youtube.com/v/elvcgVSynRg&amp;hl=en_US&amp;fs=1"
+        type="application/x-shockwave-flash" allowscriptaccess="always"
+        allowfullscreen="true" width="480" height="385"></embed>
 </object>
 
-{@link https://docs.google.com/present/edit?id=0Abz6S2TvsDWSZDQ0OWdjaF8yNTRnODczazdmZg&hl=en&authkey=CO-b7oID Presentation}
+{@link
+https://docs.google.com/present/edit?id=0Abz6S2TvsDWSZDQ0OWdjaF8yNTRnODczazdmZg&hl=en&authkey=CO-b7oID
+Presentation}
 |
-{@link https://docs.google.com/document/edit?id=1ZHVhqC0apbzPRQcgnb1Ye-bAUbNJ-IlFMyPBPCZ2cYU&hl=en&authkey=CInnwLYO Source}
+{@link
+https://docs.google.com/document/edit?id=1ZHVhqC0apbzPRQcgnb1Ye-bAUbNJ-IlFMyPBPCZ2cYU&hl=en&authkey=CInnwLYO
+Source}