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[AGL/documentation.git] / docs / 4_APIs_and_Services / 4.3_Application_Framework_Binder / 0_Overview / 0_Overview.md

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+---
+edit_link: ''
+title: Overview
+origin_url: >-
+  https://git.automotivelinux.org/src/app-framework-binder/plain/docs/afb-overview.md?h=master
+---
+
+<!-- WARNING: This file is generated by fetch_docs.js using /home/boron/Documents/AGL/docs-webtemplate/site/_data/tocs/apis_services/master/app-framework-binder-developer-guides-api-services-book.yml -->
+
+# Binder Overview
+
+The ***binder*** provides the way to connect applications to
+the services that it needs.
+
+It provides a fast way to securely offer APIs to applications
+written in any language and running almost anywhere.
+
+- The ***binder*** is developed for AGL (Automotive Grade Linux) but it is not bound to AGL.
+- The ***binder*** is the usual name.
+- The binary is named **afb-daemon**.
+- The name **afb-daemon** stands for ***Application Framework Binder Daemon***.
+
+The word *daemon*, here, denote the fact that the ***binder*** makes witchcraft to
+connect applications to their expected services. (note: that usually the term of 
+daemon denotes background process but not here).
+
+Each ***binder*** **afb-daemon** is in charge to bind one instance of 
+an application or service to the rest of the system, applications and services.  
+Within AGL, the connection between services and/or applications 
+is tuned by the AGL framework and the AGL system.
+
+## The basis of the binder
+
+The following figure shows main concepts linked to the ***binder***.
+
+<a id="fig-binder-basis"></a>
+![Figure: binder basis](pictures/basis.svg)
+
+The shown elements are:
+
+- The SECURITY CONTEXT
+
+  The primary intention of any ***binder*** is to provide
+  a secured environment for any application.  
+  On AGL, the   **security context** is ensured by [Smack] 
+  , the security context of the application or service.
+
+- The BINDER
+
+  This is the central element.  
+  It makes possible to run HTML5 applications and provides 
+  the unified access to APIs provided by the ***bindings***.
+
+  Running a pure HTML5 application doesn't require any ***binding***.  
+  In that case , the ***binder*** acts as a simple HTTP server for
+  the web runtime.
+
+- The BINDINGs
+
+  A ***binding*** adds one **API** to the ***binder***.
+
+  An **API** is a set of **verbs** that can be called
+  using either REST over HTTP or a kind of JSON RPC.
+
+  ***bindings*** are either:
+
+  - dynamically loaded libraries in the ***binder*** process
+  - remote service running on the same host
+  - remote service running on other hosts
+
+  When acting as an HTTP server, the binder treats the language
+  settings of the HTTP requests to provide internationalized
+  content as specified by
+  [widget specifications](https://www.w3.org/TR/widgets/#internationalization-and-localization).
+- The APPLICATION
+
+  An ***application*** connects to the binder to get access to
+  the **API** that it provides or to get its HTTP services to access
+  resources.
+
+<!-- pagebreak -->
+
+## Interconnection of binders
+
+The AGL framework interprets the **widget/application** manifests
+to setup the ***bindings*** configuration of the ***binders***.
+
+The figure below shows that ***binders*** are interconnected.
+
+<a id="fig-binder-interconnection"></a>
+![Figure: binder interconnection](pictures/interconnection.svg)
+
+The figure shows 4 several **application/service**: **A**, **B**,
+**C** and **D**.
+
+The application **A** might use an **API** that is shown as a
+local ***binding*** but that in reality runs within the context
+of **D**.
+
+The framework AGL takes care of making the plumbing working.