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Loose coupling

  • Glossary

"Loose coupling"

This glossary explains various keywords that will help you understand the mindset necessary for data utilization and successful DX.
This time, let's think about "loose coupling," which is useful when thinking about what IT systems and organizations should be like.

What is loose coupling?

Loose coupling refers to a state in which a system is made up of a combination of components, and the components are not highly dependent on each other, but are highly independent of each other (loose, not tight).
Although this term is primarily used in relation to IT systems, it is also a useful perspective for organizations and businesses, or for entire corporate information systems that combine multiple IT systems and cloud services. By keeping systems loosely coupled, it is possible to maintain good modifiability.

Why loose coupling is important

The explanation of loose coupling is basically as above, and some people may already know it. Even those involved in IT may have heard of it vaguely, but have a vague understanding of its meaning. Rather, I think what is difficult to understand is "why it is recommended as something necessary." Therefore, I will explain what problems arise when loose coupling is not achieved.

Monolithic (a monolithic system)

If you develop a system without any particular thought, you will almost always end up with a monolithic system. This is called a monolithic system, where the individual parts of the system are not separated, and the whole is a single solid unit like a single rock. This is usually the case if you do not take care to intentionally separate the parts.

Monolithic systems can sometimes be created through recommendations. Some of you may be reading this and wondering if splitting up is always a good thing. Just as there are people who like the phrase "one team," this can also happen because people think it's important to unify things.

Monolithic systems also have their advantages. When it comes to IT systems, monolithic implementations tend to be more efficient and perform better. Also, while splitting the system into parts can require more considerations and increase development time, it can also eliminate these hassles and allow for smoother development.

However, problems often arise after development. Suppose your business operations have changed and you want to modify your IT system. Because the whole system is made up of one part, you need to confirm and understand which parts need to be changed and what impact the changes will have on the entire system. If changes and additions are made repeatedly after the initial development, it becomes difficult to understand what is going on, and in this state you have to check the whole system every time, making it difficult to make changes.

Because changes to a part of the system affect the whole, it becomes difficult for development teams with multiple people or teams to consider each other's work. Not only does this make development by a large number of people difficult, but it also means that software cannot be released in parts and the entire system must be released each time, which can mean that even a small change requires a lot of work to be done every time a release is made.

A monolithic system is not partitioned when it is running, making it prone to crashing all of its functionality whenever something happens.

Furthermore, since the software assets have been created with great effort, you would like to reuse them or create derivative products, but it becomes difficult to know what parts can be extracted and reused, which reduces reusability.

Such problems occur not only in IT systems but also in organizations and businesses with similar structures.

tight coupling

We now understand that problems can arise if the code is not split. But why "Let's loosely couple" rather than "Let's split"? The reason is that splitting alone often results in a "tightly coupled" state.

Even if you divide a system into components, if the components are intricately intertwined, it will not become simpler, but rather more confusing.

To avoid this, it is necessary to carefully divide the parts. However, even if the division is done properly at first, it may gradually become unclear as the parts are revised.

You need to think about how to divide the system, not just for the present, but also in anticipation of future changes. You also need to consider whether the division will allow for smooth division of labor and release within the development team. If you are considering reuse, you need to take that into consideration as well. If you don't take these various considerations into account, breaking down the system into parts may not bring good results.

In this "bad state," there are unnecessarily complex dependencies (such as function calls) between components (each part of the system), and each part is (unnecessarily) tightly related. This state is called "tight coupling."​

Loose coupling

To avoid these problems, systems are divided into components that are designed to avoid tight coupling, which is called "loose coupling." Below, we will use the development of IT systems as an example, but similar things can happen with other systems, such as organizational or business design.

The connections are loose and each part is highly independent.

A state in which the overall structure is carefully designed to avoid tight coupling and reduce the dependencies between each part is called "loose coupling."

It's easier to understand (you don't have to understand everything)

As each part becomes more independent and only has organized calls and relationships with other parts of the system, you only need to understand that part thoroughly. There are fewer situations where you need to check and understand the entire system, which improves efficiency and quality in development and operation.

It becomes easier to make changes (it becomes easier to check the impact of changes)

When making changes to a certain part, the parts affected by the change are localized. This makes it easier to make changes, and it also makes it easier to check the scope of the impact and confirm whether the change is okay. If system changes can be made quickly and at low cost, business can be deployed quickly, which means that the speed and efficiency of business itself will be improved.

Easier to make changes in the future

Appropriate decoupling also makes future changes smoother. Generally, system modifications are more difficult than new development and often place a burden on developers, but this problem is alleviated.

Furthermore, it also reduces the complexity of the system after the change due to modifications. Reducing the complexity of the system due to modifications leads to a longer lifespan of the system. In other words, it not only reduces current complexity, but also reduces future complexity.

Smooth development by multiple people

Fewer dependencies mean that it's easier to neatly divide the scope of each task, facilitating development by multiple people or teams. Release work also requires less overall coordination, allowing each part to proceed independently.

Reusability and interchangeability of parts

Being organized and divided into parts facilitates reuse, making it easier to develop new systems quickly and at low cost using existing assets, or to share the same modules across multiple systems.

Furthermore, it will be easier to replace the components you are using, making it easier to replace the OS-dependent parts of an app made for Linux so that it can run on Windows.

Furthermore, by preparing reusable components based on the "business components," you can create an environment in which you can quickly develop the necessary systems by combining components according to business needs.

Integration with cloud and other companies' systems

Even if you think that deep optimization of a monolithic system is ideal, this is not possible when integrating with cloud services or other companies' systems, because you cannot change the specifications of the cloud service to suit your company's needs.

Collaboration with other companies via IT is likely to become increasingly common in the future, but the more extensive the collaboration, the more likely it will be necessary to collaborate based on a loosely coupled approach rather than through close coordination with other companies.

How to achieve loose coupling

The first thing to do is to understand and be aware of the concept of loose coupling. For those who think that thorough, close teamwork is a great thing, what I have written so far may not have been a consideration.

Another point is that simply dividing the system is not enough, and dividing the system also incurs costs. Division requires design sense, and the extent and manner of division also require judgment and design sense.

Recently, the idea of microservices has been gaining attention in cloud system development, where a system is developed by dividing it into many small, independent units. However, some argue that a monolithic application (modular monolith) with a loosely coupled internal logical structure is more realistic.

Appropriate design sense is required depending on the situation, but for organizations there is organizational design theory, and for software there is the world of software design methodology, which has been the subject of much discussion for many years. The following is a simple guide to how to think about it.

  • Are the components properly completed?
    When you need to call various things to do something, the entire structure of the call relationships will inevitably become tightly coupled. On the other hand, doing everything internally will make the system bloated, so it is necessary that the things needed to "do something" are completed at an appropriate level within the components.
  • What should/ should not beavailable from the outside
    By calling through an official interface that is organized in the form of an API or the like and maintained over the long term, it becomes less likely that dependencies that are difficult to manage and maintain (such as direct calls to internal module functions) will arise.
  • Separating and organizing things that shouldn't be together
    Not only when things that are clearly unrelated are grouped together, but also when things that are actually slightly different are grouped together without sufficient consideration, the result can become difficult to understand and complicated.
  • Don't scatter common parts or common concepts
    Having the same thing scattered around a system for no reason is not a good thing. For example, if each system has its own implementation of printing, it might make sense to combine them into one. By consolidating common concepts, concerns, and responsibilities instead of distributing them, you can often simplify semantic complexity.
  • Finding and modeling "essence" and "invariance"
    For example, if you are creating a business system, modeling that reflects the essence of the business and its functions will ensure high-quality loose coupling and reusability that are linked to the essence of the business. Also, focusing on elements that do not change over time or over time will make it easier to maintain the structure for a long period of time.
  • Using a "connecting" method: Do not call directly, use a collaboration platform
    By using a "connecting" method, you can reduce the complexity of dependencies. This can sometimes ease the dependencies that arise from individual connections, and make it easier to manage and change the entire connection.
    For example, When a system directly calls the functions of other systems, it is easy for complex, many-to-many interdependencies to occur between the caller and the callee. However, Instead of calling it directly, write it to a file and then connect it. Dependencies are organized around the relationship between each system and a common file format, which can also be considered a form of loose coupling.
    Also, EAI or iPaaS If we use these "connecting" technologies as a collaboration platform and aggregate collaboration processing there, Not only can integration processing be developed smoothly, but the dependencies themselves are centrally consolidated on the integration platform, making it easier to manage and organize the dependencies, which can help prevent tight coupling.

Related keywords (for further understanding)

  • EAI
    • By "connecting" systems through data integration, it is a means of linking distributed systems and data together without creating tangled, tightly coupled systems.
  • File Linkage
    • By going through a file, it can also be used as a way to reduce dependencies between the caller and the callee.
  • iPaaS
    • iPaaS is a cloud service that provides the power to "connect" systems and data.
  • API
  • Cloud integration
    • Using the cloud in conjunction with external systems and other cloud services. In order to successfully introduce and utilize cloud services, achieving cloud integration is often as important as introducing and utilizing the cloud itself.
  • Excel Link
    • Excel is an essential tool in the use of IT in the real world. By effectively linking Excel with external IT, you can make the most of Excel's strengths while smoothly promoting IT use.

If you are interested in our "Connecting" initiative,

If you are interested, please try out our products, which connect various systems such as IT systems and clouds while maintaining their independence.

The ultimate tool for connecting data: DataSpider, data integration software

"DataSpider," data integration tool developed and sold by our company, is a "connecting" tool with a long track record.

Unlike regular programming, development can be done using only a GUI (no code), without writing code. This means that it can be used by business personnel who have a good understanding of the business and can grasp the specific issues surrounding their company's silo structure.

There are many tools available that allow simple integration, but this tool is easy to use, even for non-programmers, as it only has a GUI, and it also has "high development productivity" and "full-scale performance that can serve as the foundation for business (professional use)." It can smoothly solve the problem of "connecting disparate systems and data," which is hindering the successful use of IT.

We offer a free trial version and hold online seminars where you can try out the software for free, so we hope you will give it a try.

The ultimate file sharing platform "HULFT"

Please try out HULFT, the de facto standard domestic file integration middleware with an overwhelming track record in Japan.

It has an overwhelming track record, having been used for many years as the infrastructure for financial institutions that require the highest level of support for their IT systems. A world where all environments are connected by files can be created in an instant.

File integration may seem like an old technology, but it has been used for many years as a means of achieving loose coupling by reducing the dependencies between the diverse callers and callees, as it is compatible with almost all environments and programming languages.

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