Architecture Styles - Revision history

Suhridk at 11:46, 23 April 2012

2012-04-23T11:46:00Z

2012-04-22T20:43:17Z

Heterogeneous Styles

2012-04-22T15:18:58Z

Intro

2012-04-05T17:53:09Z

Safety Executive

2012-04-05T17:44:45Z

Safety Executive

2012-04-05T17:25:18Z

Watchdog

2012-04-05T16:54:47Z

Monitor Actuator

2012-04-05T16:41:39Z

Homogeneous Redundancy

2012-04-05T16:01:11Z

Heterogeneous Styles

2012-04-04T23:28:59Z

Communicating Processes

@@ Line 114: / Line 114: @@
 * Systems are rarely built from a single style.
 * Types of heterogeneity:
-** Locational: Different style for different sub systems. e.g. one of the modules in call and return will have a shared data repository.
+** Locational: Runtime structure reveal patterns of different styles in different areas. Different style for different sub systems. e.g. one of the modules in call and return will have a shared data repository.
 ** Hierarchical: A component is part of one style. When comp is decomposed, it is structured according to a different style. For e.g. a component in a pub-sub system might be layered.
 ** Simultaneous: Any of several styles can be applicable.

@@ Line 4: / Line 4: @@
 * Define constraints: how things are allowed to interact.
 * Architectural pattern is synonym for style.
 * Defining features:
 ** Component types: e.g data store, processes etc.

← Older revision		Revision as of 17:53, 5 April 2012
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	* For larger and complex systems, safety executive provides a centralized point for safety processing.		* For larger and complex systems, safety executive provides a centralized point for safety processing.
	* Makes it simpler to verify and validate safety measures.		* Makes it simpler to verify and validate safety measures.
		+
		+	[[File:SafetyExecutive.png]]

← Older revision		Revision as of 17:44, 5 April 2012
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	== Safety Executive ==		== Safety Executive ==
		+
		+	* Uses a centralized coordinator for safety monitoring and control of system from faults.
		+	* Advanced watchdog which tracks and coordinates all safety monitoring.
		+	** Watchdog timeouts.
		+	** Faults identified by monitors.
		+	** Periodic built in test suites.
		+	** Software error assertions.
		+	* For larger and complex systems, safety executive provides a centralized point for safety processing.
		+	* Makes it simpler to verify and validate safety measures.

← Older revision		Revision as of 17:25, 5 April 2012
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	== Watchdog ==		== Watchdog ==
		+
		+	* A watchdog is a subsystem that receives messages from other subsystems on a periodic or sequential basis.
		+	* If msg arrives too late or out of sequence, watchdog takes corrective action.
		+	* Watchdogs usually simple - implemented in hardware. Software also possible.
		+	* Primary disadvantage - too simple to support complex error handling and fault recovery.
		+
		+	[[File:Watchdog.png]]

	== Safety Executive ==		== Safety Executive ==

← Older revision		Revision as of 16:41, 5 April 2012
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	[[File:HRedundancy.png]]		[[File:HRedundancy.png]]
		+
		+	== Monitor Actuator ==
		+
		+	* Special type of redundancy.
		+	* Channels are separated into monitoring and actuator channels.
		+	* The actuator channel performs the action e.g. starting the motor, lowering the wing flap.
		+	* The monitor channel keeps track of what the actuation and monitors the environment to ensure that the results of the actuator are appropriate.
		+	* The actuator itself cannot rely on the monitor - they must use separate sensors.
		+
		+	[[File:MonitorActuator.png]]

← Older revision		Revision as of 16:01, 5 April 2012
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	** Hierarchical: A component is part of one style. When comp is decomposed, it is structured according to a different style. For e.g. a component in a pub-sub system might be layered.		** Hierarchical: A component is part of one style. When comp is decomposed, it is structured according to a different style. For e.g. a component in a pub-sub system might be layered.
	** Simultaneous: Any of several styles can be applicable.		** Simultaneous: Any of several styles can be applicable.
		+
		+	= Safety and Reliability Patterns =
		+
		+	== Homogeneous Redundancy ==
		+
		+	* Uses identical channels to increase reliability.
		+	* All redundant channels are run in parallel and the output is compared.
		+	* If odd no of channels are used, majority-wins policy can be used that can detect and correct failures in the minority channels.
		+	* Advantage: reliability without additional development costs - since channels can be cloned.
		+	* Disadvantage: Can detect random faults, not errors (which are systematic faults).
		+	* Therefore protects against hardware failures.
		+
		+	[[File:HRedundancy.png]]

← Older revision		Revision as of 23:28, 4 April 2012
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	* Multiple machines - RPC. TCP etc.		* Multiple machines - RPC. TCP etc.
	* classic e.g. client server architecture. Server works synchronously or asynchronously (meaning client has his own thread of control).		* classic e.g. client server architecture. Server works synchronously or asynchronously (meaning client has his own thread of control).
		+
		+	= Heterogeneous Styles =
		+
		+	* Systems are rarely built from a single style.
		+	* Types of heterogeneity:
		+	** Locational: Different style for different sub systems. e.g. one of the modules in call and return will have a shared data repository.
		+	** Hierarchical: A component is part of one style. When comp is decomposed, it is structured according to a different style. For e.g. a component in a pub-sub system might be layered.
		+	** Simultaneous: Any of several styles can be applicable.