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--- arcs.js:framework_presentation [2017/05/26 03:24]
didier [Component model]
+++ arcs.js:framework_presentation [2017/05/26 04:26]
didier
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 ====== ARCS.js, a Web framwork for Augmented Reality ======
-===== In brief =====
 **ARCS.js** is a component oriented programming framework dedicated to augmented reality applications. It is written using the javascript language.
 The targeted platforms are:
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   * using slot calls (see invocations below).
+==== Application model ====
+In ARCS.js, an application is considered to have a lifecycle going through several different states (initialisation, normal mode, recovery mode, etc). Each state is characterized by a set of omponents and a set of signal/slot connections. Such configuration is called a **sheet**.
+The application is then controlled by a finite statemachine, each state of it corresponding to one sheet. When a transition is triggered in the statemachine, it activates a change of sheet.
+The sheet is composite structure. It contains components as well as other data:
+  * a list of pre-connection invocations for component initialization;
+  * a list of connections to establish datapath between components;
+  * a list of post-connection invocations that enables dataflow;
+  * a list of cleanup invocations in order to set some components in a stable state.
+The behavior of the application controller is the following, assuming that it received a token triggering a transition (having a starting state and an ending state):
+  - If a sheet is active (corresponding to the starting state), disconnect all components;
+  - Perform cleanup invocations on sheet;
+  - Enable the next sheet (corresponding to the ending state):
+    - Perform pre-connection invocations;
+    - Connect components of the sheet;
+    - Perform post-connection invocations.