ISA Standards and Practices

ISA Standards and Practices

 

ISA (interactive services architecture) interactive service architecture
1) Software Design Model
The ISA design team adopts the factory mode to implement the main aspects of the ISA design.
2) UML
The ISA architecture uses the Rational Rose design tool to create an object model of a complex object-oriented system.
3) Implementation of isa1.4
The implementation of isa1.4 adopts the following software:
Corba2.0
IDL
XML
IIOP as the basic Interoperability Protocol
4) ISA Object Model
Distributed object technology: corba2.0 is used as the ideal ISA compatible system:
Object-oriented capabilities
Positioning independence
Language independence
Implementation independence
Independence of hardware architecture
Operating System independence
Protocol independence
Transmission independence
5) CORBA service
CORBA provides a large number of predefined services,
(1) Naming Service
One of the key issues to be addressed in any distributed system is how to obtain object references regardless of the actual location of the object.
Object Location transparency is one of the main features of CORBA.
The CORBA Naming Service provides a Hierarchical Distributed Naming Service.
(When the server object starts to be executed, it registers itself as a special name by using the CORBA Naming Service. The client can use this name to send a request to the naming server and then

The name server returns an object reference method for the client to call the object .)
In order for the client to efficiently use the Naming Service, ISA defines a standard naming hierarchy, and the client knows the standard name of the object to be used.
(2) Naming Structure
The CORBA Naming Service stores object references in hierarchical tree structures, similar to Windows file systems.
The ISA architecture adopts a very special policy to use the CORBA Naming Service and decide the object type registered to the Naming Service. This policy is the factory in the Naming Service.

Object reference.
In the factory mode, the object is created by a standard method defined in the parent class, rather than its constructor. The specific subclass is responsible for the object to be created.

And provides a common interface to create multiple associated objects.
The factory object is the object that creates other objects.
(3) Notification Service
In a distributed system, when events of interest to some components occur, You need to notify the relevant system components.
The notification service provides a framework for sending communication messages (notifications) to objects asynchronously to remind you that the specified event has occurred.
The CORBA Notification Service uses the supplier/consumer distributed model.
The ISA event model consists of the following components:
· Push supplier (push supplier ):
An ISA component connects to the "proxy push consumer" and transmits event data to the consumer by calling an appropriate push method.
· Proxy push consumer (proxy push consumer ):
An interface supported by the event channel that acts as a proxy for all push consumers registered in the event channel, receives events, and sends them to actual consumers.
· Push consumer (push consumer ):
A isa component connected to "proxy push consumer ".
· Proxy push supplier (proxy push supplier ):
An interface supported by the event channel works on the consumer side of the event channel. The consumer connects to the "Agent pushing supplier ".
(4) Notification Service supports event delivery in three ways
· In CORBA: Any
· A cosnotification: structuredevent
· A sequence of structuredevents
Based on the type used by Event Notification, appropriate proxy consumers and suppliers must be used by their respective suppliers and consumers.
The event notification is sent to the component through the event channel.
An event channel is a CORBA object that allows other objects to communicate with each other without knowing each other.
The supplier is an object that provides event-to-event channels.
The consumer is an object that receives events from the event channel.
The process of providing events is sometimes to call the publishing event.
The notification service provides QoS settings that allow applications to control the QoS required for event message delivery.
The ISA event model uses the Notification Service's communication push event model. (In this model, each individual pays attention to the proxy consumer provided by the event channel. The agent consumer receives

Receive event communication, and then use the agent supplier to transmit event data to the actual consumer. Simply put, the supplier calls the consumer interface to push events.
(5) Event Filtering
The notification service supports Event Filtering to filter events by event consumers.
The event consumer can define a filter, which encapsulates a set of restrictions and adds them to the proxy or admin.
The filter contains a restriction expression, which defines the criteria for filtering.
Each restriction expression is composed of a sequence of event types. The restriction language is used. The default restriction language is extended_tcl.