middleware

Middleware is computer software that connects software components or applications. The software consists of a set of services that allows multiple processes running on one or more machines to interact across a network. This technology evolved to provide for interoperability in support of the move to coherent distributed architectures, which are used most often to support and simplify complex, distributed applications. It includes web servers, application servers, and similar tools that support application development and delivery. Middleware is especially integral to modern information technology based on XML, SOAP, Web services, and service-oriented architecture.

Middleware sits "in the middle" between application software working on different operating systems. It is similar to the middle layer of a three-tier single system architecture, except that it is stretched across multiple systems or applications. Examples include database systems, telecommunications software, transaction monitors, and messaging-and-queueing software.

The distinction between operating system and middleware functionality is, to some extent, arbitrary. While core kernel functionality can only be provided by the operating system itself, some functionality previously provided by separately sold middleware is now integrated in operating systems. A typical example is the TCP/IP stack for telecommunications, nowadays included in virtually every operating system.

In simulation technology, middleware is generally used in the context of the high level architecture (HLA) that applies to many distributed simulations. It is a layer of software that lies between the application code and the run-time infrastructure. Middleware generally consists of a library of functions, and enables a number of applications – simulations or federates in HLA terminology – to page these functions from the common library rather than re-create them for each application

Definitions

Middleware is software enterprise application integration. It describes a piece of software that connects two or more software applications, allowing them to exchange data....

ObjectWeb defines middleware as: "The software layer that lies between the operating system and applications on each side of a distributed computing system in a network."^[1]

Origins

Middleware is a relatively new addition to the computing landscape. It gained popularity in the 1980s as a solution to the problem of how to link newer applications to older legacy systems, although the term had been in use since 1968.^[2] It also facilitated distributed processing, the connection of multiple applications to create a larger application, usually over a network.

Organizations

IBM, Red Hat, and Oracle Corporation are major vendors providing middleware software. Vendors such as Axway, SAP, TIBCO, Mercator Software, Crossflo, Vitria and webMethods were specifically founded to provide Web-oriented middleware tools. Groups such as the Apache Software Foundation and the ObjectWeb Consortium encourage the development of open source middleware.

Use of middleware

Middleware services provide a more functional set of application programming interfaces to allow an application to:

• Locate transparently across the network, thus providing interaction with another service or application
• Be independent from network services
• Be reliable and always available

when compared to the operating system and network services.

Middleware offers some unique technological advantages for business and industry. For example, traditional database systems are usually deployed in closed environments where users access the system only via a restricted network or intranet (e.g., an enterprise’s internal network). With the phenomenal growth of the World Wide Web, users can access virtually any database for which they have proper access rights from anywhere in the world. Middleware addresses the problem of varying levels of interoperability among different database structures. Middleware facilitates transparent access to legacy database management systems (DBMSs) or applications via a web server without regard to database-specific characteristics ^[3]. Businesses frequently use middleware applications to link information from departmental databases, such as payroll, sales, and accounting, or databases housed in multiple geographic locations ^[4]. In the highly competitive healthcare community, laboratories make extensive use of middleware applications for data mining, laboratory information system (LIS) backup, and to combine systems during hospital mergers. Middleware helps bridge the gap between separate LISs in a newly formed healthcare network following a hospital buyout ^[5]. Wireless networking developers can use middleware to meet the challenges associated with wireless sensor network (WSN), or WSN technologies. Implementing a middleware application allows WSN developers to integrate operating systems and hardware with the wide variety of various applications that are currently available ^[6]. Middleware can help software developers avoid having to write to application programming interfaces (API) for every control program, by serving as an independent programming interface for their applications. Finally, e-commerce uses middleware to assist in handling rapid and secure transactions over many different types of computer environments ^[7]. In short, middleware has become a critical element across a broad range of industries, thanks to its ability to bring together resources across dissimilar networks or computing platforms.

In 2004 members of the European Broadcasting Union (EBU) carried out a study of Middleware with respect to system integration in broadcast environments. This involved system design engineering experts from 10 major European broadcasters working over a 12 month period to understand the effect of predominantly software based products to media production and broadcasting system design techniques. The resulting reports were published and are freely available from the EBU web site here:- Tech 3300 ^[8] and Tech 3300s ^[9]

Types of middleware

Hurwitz's classification system organizes the many types of middleware that are currently available.^[10]. These classifications are based on scalability and recoverability:

• Remote Procedure Call — Client makes calls to procedures running on remote systems. Can be asynchronous or synchronous.
• Message Oriented Middleware — Messages sent to the client are collected and stored until they are acted upon, while the client continues with other processing.
• Object Request Broker — This type of middleware makes it possible for applications to send objects and request services in an object-oriented system.
• SQL-oriented Data Access — middleware between applications and database servers.
• Embedded Middleware — communication services and integration interface software/firmware that operates between embedded applications and the real time operating system.

Other sources include these additional classifications:

• Transaction processing monitors — Provides tools and an environment to develop and deploy distributed applications.^[11]
• Application servers — software installed on a computer to facilitate the serving (running) of other applications.
• Enterprise Service Bus — An abstraction layer on top of an Enterprise Messaging System.

See also

Look up middleware in Wiktionary, the free dictionary.

• Comparison of business integration software
• Middleware Analysts
• Service Oriented Architecture
• Enterprise Service Bus
• Event-driven SOA
• ObjectWeb

References

External links

• Internet2 Middleware Initiative
• Dynamically Self Configuring Automotive Systems
• Middleware Abstraction Layer
• SWAMI - Swedish Alliance for Middleware Infrastructure
• Element (commercial offering from Enea)
• Open Middleware Infrastructure Institute (OMII-UK)
• Common XML Vocabularies
• Specific XML Vocabularies
• [1] European Broadcasting Union (EBU) Middleware report.
• [2] More detailed supplement to the European Broadcasting Union Middleware report.
• ObjectWeb - international community developing open-source middleware