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Update concepts doc with a new diagram

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Raymond Feng 2013-09-06 15:46:36 -07:00
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@ -7,7 +7,7 @@ answer a couple of questions:
> What _is_ LoopBack? > What _is_ LoopBack?
- A component in the [StrongLoop Suite](www.strongloop.com/strongloop-suite). - A component in the [StrongLoop Suite](http://www.strongloop.com/strongloop-suite).
- A library of Node.js modules for connecting mobile apps to a variety of data - A library of Node.js modules for connecting mobile apps to a variety of data
sources. sources.
- A command line tool, `slc lb`, for generating models and entire applications - A command line tool, `slc lb`, for generating models and entire applications
@ -16,39 +16,49 @@ answer a couple of questions:
> How does LoopBack work? > How does LoopBack work?
LoopBack Applications are made up of three components: - LoopBack applications are made up of three components:
[Data Sources](#data-sources-and-connectors) (also referred to as "Connectors"), [Models](#models), [Data Sources/Connectors](#data-sources-and-connectors), and the
[Models](#models), and the [Mobile Clients](#mobile-clients) that consume them. [Mobile Clients](#mobile-clients) that consume them.
Any mobile or web app can interact with a LoopBack Data Source through the Model - Any mobile or web app can interact with LoopBack through the Model API that are
API. The Model API is available [locally within Node.js](#model), [remotely over backed by various data sources. The Model API is available
REST](#rest-api), and as native mobile SDKs for [iOS, Android, and [locally within Node.js](#model), [remotely over REST](#rest-api), and as native
HTML5](#mobile-clients). Using the API, clients can query databases, store data, mobile SDKs for [iOS, Android, and HTML5](#mobile-clients). Using the API,
upload files, send emails, create push notifications, register users, and any clients can query databases, store data, upload files, send emails, create push
other behavior provided by data sources. notifications, register users, and any other behavior provided by data sources.
![concepts](loopback-concepts.png "LoopBack Concepts")
### Mobile Clients ### Mobile Clients
**PLACEHOLDER FOR SDK INTRO** **PLACEHOLDER FOR SDK INTRO**
In summary, mobile clients work with objects that are connected to LoopBack
to provide data and perform actions.Those objects are captured as models in
LoopBack.
### Models ### Models
> What is a Model? > What is a Model?
In LoopBack, a Model consists of the following: A LoopBack Model consists of the following:
- Application data - Application data
- Validation rules - Validation rules
- Data access capabilities
- Business logic - Business logic
A mobile client uses the remote API provided by Models to request any A mobile client uses the remote API provided by Models to request any
information needed to display a useful interface to the user. information needed to display a useful interface to the user or trigger actions
on the models to interact with backend systems.
#### A Simple Example Let's use a simple example to explain what a model can do for you.
#### Defining a model
For example, an e-commerce app might have `Product` and `Inventory` Models. For example, an e-commerce app might have `Product` and `Inventory` Models.
A mobile client could use the `Product` Model API to search through all of the A mobile client could use the `Product` Model API to search through all of the
Procuts in a database. A client could join the `Product` and `Inventory` data to Products in a database. A client could join the `Product` and `Inventory` data to
determine what products are in stock, or the `Product` Model could provide a determine what products are in stock, or the `Product` Model could provide a
server-side function (or [remote method](#remote-methods)) that aggregates this server-side function (or [remote method](#remote-methods)) that aggregates this
information. information.
@ -60,17 +70,22 @@ var Product = Model.extend('product');
var Inventory = Model.extend('customer'); var Inventory = Model.extend('customer');
``` ```
**NOTE:** Models are _schema-less_ by default, but some Connectors, such as **NOTE:** Models are _schema-less_ by default, but some data sources, such as
relational databases, _require_ schemas. Additionally, schemas are immensely relational databases, _require_ schemas. Additionally, schemas are immensely
valuable for validating sanitizing data coming from mobile clients. See valuable for establishing the common knowledge of business data so that the data
[Sanitizing and Validating Models](#sanitizing-and-validating-models) if your exchange can be agreed and documented while data coming from mobile clients can
application needs to connect to an RDBMS, for example. be validated and/or sanitized . See [Sanitizing and Validating Models](#sanitizing-and-validating-models)
if your application needs to connect to an RDBMS, for example.
#### Attaching Data Sources #### Attaching to Data Sources
Attaching a Model to a Data Source gives you access to a powerful API mixed into Instances of a Model carry application data. But they are not very interesting
Models by their Sources. The [MongoDB Connector](#), for example, mixes in a until applications can create, retrieve, update, or delete (CRUD) model instances.
`create` method that allows us to store a new Product in the database: LoopBack introduces the DataSource concept to provide the data access
capabilities to models. Attaching a Model to a DataSource gives you access to a
powerful API mixed into Models by the Connector behind a DataSource. The
[MongoDB Connector](#), for example, mixes in a `create` method that allows us
to store a new Product in the database:
```js ```js
// Step 2: Attach Data Sources // Step 2: Attach Data Sources
@ -87,6 +102,9 @@ Product.create({ name: 'widget', price: 99.99 }, function(err, widget) {
}); });
``` ```
Now the models have both data and behaviors. How can the mobile clients benefit
from them? We need a way to make the models available from mobile clients.
#### Exposing to Mobile Clients #### Exposing to Mobile Clients
Models can be exposed to mobile clients using one of the remoting middlewares. Models can be exposed to mobile clients using one of the remoting middlewares.
@ -104,11 +122,16 @@ app.use(loopback.rest());
app.model(Product); app.model(Product);
``` ```
After this, you'll have the `Product` model with CRUD functions working remotely
from the mobile clients. Please note the model is schema-less till now and the
data are not checked.
#### Sanitizing and Validating Models #### Sanitizing and Validating Models
Once a schema is added to a Model, it will validate and sanitize data before A Model can be described in plain json or JavaScript. The description is called
giving it to a Data Source. For example, the `Product` Model has a schema that schema. Once a schema is defined for a Model, it will validate and sanitize data
will not change. The example below updates the `Product` Model with a schema before giving it to a Data Source. For example, the `Product` Model has a schema
that will not change. The example below updates the `Product` Model with a schema
written in **LoopBack Definition Language**, a well-documented flavor of JSON. written in **LoopBack Definition Language**, a well-documented flavor of JSON.
```js ```js
@ -137,12 +160,8 @@ required `name` property.
### Data Sources and Connectors ### Data Sources and Connectors
LoopBack allows you to connect to many sources of data and services both in the Now you see the power of LoopBack models. A model gets rich set of functions out
cloud and on-premise in your data center. These sources of data and services are of the box with the contribution from Data Sources and Connectors.
called DataSources. DataSources are accessed through a plugin called a Connector
in LoopBack. Plugins are highly customizable and extensible. Unlike other
mobile backend, LoopBack can leverage your existing data and organize them in
the form of models.
The concept of DataSource is introduced to encapsulate business logic to The concept of DataSource is introduced to encapsulate business logic to
exchange data between models and various data sources. Data sources are exchange data between models and various data sources. Data sources are
@ -150,10 +169,16 @@ typically databases that provide create, retrieve, update, and delete (CRUD)
functions. LoopBack also generalize other backend services, such as REST APIs, functions. LoopBack also generalize other backend services, such as REST APIs,
SOAP Web Services, and Storage Services, as data sources. SOAP Web Services, and Storage Services, as data sources.
Data sources are backed by connectors which implement the data exchange logic LoopBack allows you to connect to many sources of data and services both in the
using database drivers or other client APIs. In general, connectors are not used cloud and on-premise in your data center. DataSources are accessed through a
directly by application code. The DataSource class provides APIs to configure plugin called a Connector in LoopBack. Plugins are highly customizable and
the underlying connector and exposes functions via DataSource or model classes. extensible. Unlike other mobile backend, LoopBack can leverage your existing
data and organize them in the form of models.
Connectors implement the data exchange logic using database drivers or other
client APIs. In general, connectors are not used directly by application code.
The DataSource class provides APIs to configure the underlying connector and
exposes functions via DataSource or model classes.
#### LoopBack Connector Modules #### LoopBack Connector Modules
@ -168,7 +193,7 @@ For more information, please read the [LoopBack DataSource and Connector Guide](
### REST ### REST
Everything defined in LoopBack (e.g. Models) can be made available as a REST Functions defined in LoopBack Models can be made available as a REST
endpoint. You can see and experiment with _your_ REST api using the endpoint. You can see and experiment with _your_ REST api using the
[LoopBack API Explorer](http://localhost:3000/explorer/). [LoopBack API Explorer](http://localhost:3000/explorer/).

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