In computer science, systems are typically divided into two categories: software and hardware. However, there is an additional layer in between, referred to as middleware, which is a software pipeline—an operation, a process, or an application between the operating system and the end user. This article aims to define middleware and reflect on its necessity, as well as address controversies about when and where it applies. It also explores the application of middleware in emerging technologies such as cloud computing and the Internet of Things (IoT), as well as future middleware developments.
The term was introduced in the early 1980s. It encompasses complex software solutions that modernize legacy systems—typically mainframes—through new features such as software and application components. Initially, it was solely used to expand the layer separating the network and application layers. Subsequently, its use expanded to serve as the layer above the operating system and network layer, and below the application layer. This means that middleware could now facilitate the generic communication between the application component and the distributed network.
Through middleware, a programmer has the option to implement a decentralized solution instead of having to interact and analyze different components.
In recent literature multiple definitions have been used, depending on the field of research. On the one hand, both a software and a DevOps engineer would describe middleware as the layer that “glues” together software by different system components; on the other hand, a network engineer would state that middleware is the fault-tolerant and error-checking integration of network connections. In other words, they would define middleware as communication management software. A data engineer, meanwhile, would view middleware as the technology responsible for coordinating, triggering, and orchestrating actions to process and publish data from various sources, harnessing big data and the IoT. Given that there is no uniform definition of middleware, it is best to adopt a field-specific approach.
The main categories of middleware are as follows:
- Transactional. Processing of multiple synchronous/asynchronous transactions, serving as a cluster of associated requests from distributed systems such as bank transactions or credit card payments.
- Message-oriented. Message queue and message passing architectures, which support synchronous/asynchronous communication. The first operates based on the principle that a queue is used to process information, whereas the second typically operates on a publish/subscribe pattern where an intermediate broker facilitates the communication.
- Procedural. Remote and local architectures to connect, pass, and retrieve software responses of asynchronous communications such as a call operation. Specifically, the first architecture calls a predetermined service of another computer in a network, while the second interacts solely with a local software component.
- Object-oriented. Similar to procedural middleware, however, this type of middleware incorporates object-oriented programming design principles. Analytically, its software component encompasses object references, exceptions, and inheritance of properties via distributed object requests. It is typically used synchronously, because it needs to receive a response from a server object to address a client action. Importantly, this type of middleware can also support asynchronous communication via the use of (multi) threads and generally concurrent programming.
Academics have further segregated middleware depending on the application module it serves, such as database and Web server. There are several types of middleware, falling into these key categories: reflective, agent, database, embedded, portal, and device (or robotics).
First, reflective middleware constitutes components that are specifically designed to “easily operate with other components and applications,” while agent middleware has multiple components that operate on complex domain-specific languages and laws.
Second, database middleware focuses on DB-to-DB or DB-to-apps communication—either natively or via call-level interfaces (CLIs)—while embedded middleware acts as the intermediary for embedded integration apps and operating-system communication.
Third, portal middleware creates a context-management tool in a composite, single-screen application, while device (or robotics) middleware simplifies the integration of specific device operating systems or robotic hardware and firmware.
The first categorization is broader, emphasizing architecture operating principles, while the second categorization is application-driven. For this reason, the first segregation is preferable to define middleware accurately per architecture integration instead of its application properties.
This article originally appeared on alexandriadispatch.com. To read the full article, click here.
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