Enterprise messaging system - AbsoluteAstronomy.com

An enterprise messaging system (EMS) is a set of published Enterprise-wide standards that allows organizations to send semantically precise messages between computer systems. EMS systems promote loosely coupled

Loose coupling

In computing and systems design a loosely coupled system is one where each of its components has, or makes use of, little or no knowledge of the definitions of other separate components. The notion was introduced into organizational studies by Karl Weick...

architectures that allow changes in the formats of messages to have minimum impact on message subscribers. EMS systems are facilitated by the use of XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

messaging, SOAP and web service

Web service

A Web service is a method of communication between two electronic devices over the web.The W3C defines a "Web service" as "a software system designed to support interoperable machine-to-machine interaction over a network". It has an interface described in a machine-processable format...

s.

EMS usually take into account the following considerations:

Security: Messages must be encrypted if they travel over public interfaces. Messages must be authenticated or digitally signed if the receiver is to have confidence that the messages have not been tampered with in transit.
Routing: Messages need to be routed efficiently from the sender to the receiver. Intermediate nodes may need to route the messages if the body of the message is encrypted.
Metadata: The body of the document contains information that must be unambiguously interpreted. Metadata registries should be used to create precise definitions for each data element.
Subscription: Systems should be able to subscribe to all messages that match a specific pattern. Messages with a specific content may be routed differently. For example some messages may have different priority or security policies.
Policy: Enterprise messaging systems should provide some consideration for a centralized policy of messages such as what classes or roles of users can access different fields of any message.

Separation of message header and message body

The design of an EMS is usually broken down into two sections:

Message header design – Message headers contain the information necessary to route messages. Message headers are usually coded in clear text so that intermediate nodes receive all the necessary information they need to route and prioritize the message. Message headers are analogous to the information printed on the outside of a letter (to, from, priority of message etc.)
Message body semantics – Message body semantics include the precise definition of all of the data element
Data element
In metadata, the term data element is an atomic unit of data that has precise meaning or precise semantics. A data element has:# An identification such as a data element name# A clear data element definition# One or more representation terms...

s in the body of the message. Message semantics
Semantics
Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

can be aided by the use of a precise data dictionary that documents metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

.

Comparisons

Although similar in concept to an Enterprise Service Bus

Enterprise service bus

An enterprise service bus is a software architecture model used for designing and implementing the interaction and communication between mutually interacting software applications in Service Oriented Architecture...

(ESB), an EMS places emphasis on design of messaging protocols, not the implementation of the services using a specific technology such as web services or Java Message Service

Java Message Service

The Java Message Service API is a Java Message Oriented Middleware API for sending messages between two or more clients. JMS is a part of the Java Platform, Enterprise Edition, and is defined by a specification developed under the Java Community Process as JSR 914...

.

Note that an Enterprise Messaging System should not be confused with an electronic mail system used for delivering human readable text messages to individual people.

An example of a specific application programming interface

Application programming interface

An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...

(API) that implements an Enterprise Messaging System is the Java Message Service

Java Message Service

(JMS). Although this is an API it embodies many of the same issues involved in setting up a full EMS.

Policy statements may also be extracted from a centralized policy server. These policy statements can be expressed in the XML Access Control Markup Language

XACML

XACML stands for eXtensible Access Control Markup Language. The standard defines a declarative access control policy language implemented in XML and a processing model describing how to evaluate authorization requests according to the rules defined in policies.As a published standard...

(XACML).

External links

J2EE Connector architecture and enterprise application integration by Rahul Sharma, Beth Stearns, Tony Ng

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Separation of message header and message body

Comparisons

See also

External links