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architecture_styles [2015/02/26 21:47]
apaschke [Introduction: Software Communication]
architecture_styles [2015/04/24 14:11] (current)
rmbell [Introduction: Software Communication]
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 ===== Introduction:​ Software Communication ===== ===== Introduction:​ Software Communication =====
  
-The two things needed for software ​communication ​are a message transport ​and a message protocol. A message transport is the physical means to convey a message. Examples of transport mechanisms include Ethernet, shared memory, and the Peripheral Component Interconnect (PCI) bus. Wi-Fi and Bluetooth are examples of wireless transports.+Software ​communication ​requires ​a message transporta message protocol, and a destination address. A message transport is the physical means to convey a message. Examples of transport mechanisms include Ethernet, shared memory, and the Peripheral Component Interconnect (PCI) bus. Wi-Fi and Bluetooth are examples of wireless transports.
  
-If the source and destination happen to be in the same virtual address space; the transport can be optimized into a set of parameters that are passed in a simple ​function ​call. Otherwise communication must take place through ​transport facilityVirtually ​all CORBA implementations automatically recognize when this optimization can be used.+All three concepts of transport, protocol, and destination address are interrelated. A change to one affects the others. For example: if the source and destination happen to be in the same virtual address space; the source will know the virtual address ​of the receiving ​function ​and will know how to invoke it and how to pass message through parametersNearly ​all CORBA implementations automatically recognize when this optimization can be used
 + 
 +A simple function call is not possible when the source and destination are physically separated. Distributed software communication is accomplished by serializing the message according to a protocol that destination understands. A remote destination addresses could be something simple like the combination of an IP address and port number or it could be expressed as a URL, or an IRI, or a CORBA Inter-operable Object Reference (IOR).
  
 All physical message transports including Ethernet and Wi-Fi just transport bytes. It is left up to the source and destination to agree on a message protocol. The protocol specifies the set of rules for how these messages will be serialized for transport. A protocol could be ad-hoc and unsophisticated or it might have the sophistication necessary for the source and destination to remain oblivious of the distributed nature of the system. This in turn allows the developer to choose the style that best fits the application. All physical message transports including Ethernet and Wi-Fi just transport bytes. It is left up to the source and destination to agree on a message protocol. The protocol specifies the set of rules for how these messages will be serialized for transport. A protocol could be ad-hoc and unsophisticated or it might have the sophistication necessary for the source and destination to remain oblivious of the distributed nature of the system. This in turn allows the developer to choose the style that best fits the application.
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 ===== Direct Strongly-Coupled API4KB Access ​ ===== ===== Direct Strongly-Coupled API4KB Access ​ =====
  
-Strong coupling with the local API4KB ​requiring direct knowledge of the (downloaded) API4KB ​libraries and knowledge artifacts ​or direct knowledge about how the inter-process interaction with the remote API4KB works in ad-hoc network programming (e.g. via socket programming).+Strong coupling with the local client ​requiring direct knowledge of the (downloaded) API4KB ​**Artifacts** ​or direct knowledge about how the inter-process interaction ​and access ​with the remote API4KB works in ad-hoc network programming (e.g. via socket programming).
  
-Example: OntoMaven and RuleMaven.+Example: ​[[http://​www.corporate-semantic-web.de/​ontomaven.html|OntoMaven and RuleMaven]].
  
  
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 A unit of composition with contractually specified interfaces and explicit content dependencies only. Component is specified in terms of a contract which includes a set of provided interfaces (interfaces that the component offers as a service to other components) and required interfaces (dependencies that this component has on other components). Container provides managed server-side hosting environment for components and deals with the distributed systems and middleware issues. ​ A unit of composition with contractually specified interfaces and explicit content dependencies only. Component is specified in terms of a contract which includes a set of provided interfaces (interfaces that the component offers as a service to other components) and required interfaces (dependencies that this component has on other components). Container provides managed server-side hosting environment for components and deals with the distributed systems and middleware issues. ​
  
-Examples, e.g. Java Beans, Corba Component Model, ​API4KB ​OntoMaven Aspect-Oriented Component Model, ...+Examples, e.g. Java Beans, Corba Component Model, ​[[http://​www.corporate-semantic-web.de/​ontomaven.html|OntoMaven Aspect-Oriented Component Model]], ...
  
 ===== Decoupled Indirect Communication ===== ===== Decoupled Indirect Communication =====
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 Publish-subscribe with event-based communication through propagation of events (via an underlying overlay network, e.g. structured and unstructured peer-to-peer or other broker overlay). Publishers publish structured events to an event service (responsible for event routing and matching) and subscribers express interest in particular events through subscriptions. Publish-subscribe with event-based communication through propagation of events (via an underlying overlay network, e.g. structured and unstructured peer-to-peer or other broker overlay). Publishers publish structured events to an event service (responsible for event routing and matching) and subscribers express interest in particular events through subscriptions.
  
-Distributed Event Based Systems with Complex Event Processing (CEP) in Event Processing Agents (EPAs) deployed in Event Processing Networks (EPNs). ​+Distributed Event Based Systems ​and Event Streaming ​with Complex Event Processing (CEP) in Event Processing Agents (EPAs) deployed in Event Processing Networks (EPNs). ​
  
 ==== Group communication ==== ==== Group communication ====
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 Examples, e.g. Tuple Spaces, Distributed Shared Memory, Message Queues (e.g., JMS, Active MQ, ...) Examples, e.g. Tuple Spaces, Distributed Shared Memory, Message Queues (e.g., JMS, Active MQ, ...)
  
-==== Asynchronous Messaging Libraries ====+====  Asynchronous Messaging Libraries ==== 
 + 
 +Libraries exist which combine and can be used according to a number of the different, above mentioned messaging patterns, e.g.
  
-Libraries exist which can be used according to a number of different ​messaging ​patterns.+  * [[http://​en.wikipedia.org/​wiki/​%C3%98MQ|0MQ]] (ZeroMQ) is a lightweight messaging system specially designed for high throughput and low latency scenarios as in IoT, low-level event streaming etc. It  provides "​sockets"​ (a many-to-many connection generalizing the concept of network socket) ​which each operate ​according to a specific ​messaging ​pattern (e.g. RPC, pub-sub, ...), which (in contrast to e.g. more advanced messaging queue servers and enterprise service bus middlewares) need to be manually implement by combining various pieces of the framework (see ad-hoc network programming with sockets and devices in strong coupling category). 
 +  * higher-level message queue middleware such as Erlang (RabbitMQ), C (beanstalkd),​ Ruby (Starling or Sparrow), Scala (Kestrel, Kafka) or Java (ActiveMQ), and Enterprise Service Bus middleware such as OpenESB, Mule ESB, ...
  
-  * [[http://en.wikipedia.org/​wiki/​%C3%98MQ|0MQ]] (ZeroMQprovides "​sockets"​ (a many-to-many connection generalizing ​the concept ​of network socket) which each operate according to a specific messaging pattern (e.g. RPCpub-sub, ...)+Examples, e.g. [[http://responder.ruleml.org|RuleML RuleResponder]] is implemented as a Staged Event-Driven Architecture ​(SEDAusing the Mule ESB and ActiveMQ or RabbitMQ. It can use all kinds of synchronous and asynchronous transport protocols including ​e.g. AMQPJMSHTTP Rest, SOAP, etc..
  
 ===== Summary of Dimensions ===== ===== Summary of Dimensions =====
architecture_styles.1424987279.txt.gz · Last modified: 2015/02/26 21:47 by apaschke