How To Measure Modularity

A module is a set of parts that can be used to build a more complex system. How parts can be set or grouped together is based on some considerations. How optimised our module or how good the modularity level of our system is, are our questions.

Several aspects are very common when we want to measure the modularity of our system or software: cohesion, coupling, and connascence.

Cohesion

It is the indicator of whether we efficiently group some parts together. A cohesive module means all parts in the module are well coupled. If we break a cohesive module in our code into pieces or smaller modules, that will lead to an increase in coupling across modules and a decrease in the readability of the code.

There are a few types of cohesion based on the cause of cohesiveness such as functional, sequential (input-output relation), procedural (execution order), logical, or temporal. One that is not strongly related to the functional aspect is logical cohesion. For example, we may group several unrelated functions together into a module just because the functions are similarly used to manipulate a certain data type.

There is a value used to measure cohesion level called LCOM (Lack of Cohesion in Module). The value is equal to the sum of sets of methods that are not shared via shared fields or variables. For example, a class has a function, called X, that only accesses one variable; and also another function, called Y, that only accesses different other variables. This will result in a high value of LCOM which is discouraged.

Coupling

Unlike cohesiveness which sometimes can be quite subjective, coupling can be measured by the number of connections going in and out of a part. Afferent coupling is the number of connections going into a part. Efferent coupling is the number of connections going out to other parts.

There are three attributes related to coupling which are abstractness, instability, and distance from the main sequence.

Abstractness is the sum of abstract elements (e.g. interface, abstract class) divided by the sum of concrete elements (non-abstract components) or actual program code. Too many abstractions can confuse developers in how to work with the code.

Instability is a ratio between the number of efferent coupling and the total of coupling (efferent and afferent). So, instability can be high (close to 1) if efferent coupling is far greater than afferent coupling.

The main sequence is the ideal relationship between abstractness and instability. Let's see the following picture that explains everything.

The value of the distance from the main sequence can be approximated as the absolute value of abstractness + instability - 1. If our code has many abstractions and also the efferent coupling is very high, our code is in the zone of uselessness. If we have a big code base with very little abstraction, the code is in the zone of pain.

Connascence

Connascence is the correlation of one part with other parts in a system concerning maintaining system correctness caused by certain modifications in one part. There are two categories of connascence, static (source-code level coupling) and dynamic (execution-time coupling).

Static

Name, like the name of variables
Type, like the structure of an object
Meaning, like the meaning of certain constant value
Position, like the order of function arguments
Algorithm, like an authorization mechanism

Dynamic

Execution, like the order of executing methods of an object
Timing, like the order of executing two separate processes
Values, like values in primary and backup databases
Identity, like objects communicated in a distributed queue

There are three properties related to connascence level which are strength, locality, and degree. Strength indicates the effort needed for a developer to refactor the coupling. Locality indicates how close modules are to each other. The degree indicates the size of the impacts of changes. Let's take a look at the following image that shows the strength of connascence.

Connascence of name is the lowest because of the easiness of refactoring and advances in today's code editor for replacing variables. Connascence of position has higher strength, imagine we change the order of arguments in a function, then we should refactor all parts that call the function.

All three properties should be considered when we design the modularity in our system. When there are far-separated parts that mean a low level of locality, it is better to have lower strength connascence. When the parts are in the same class that means a high level of locality, it is fine to have higher strength connascence. If we have parts with a high strength connascence, it is still fine when the parts are rarely implemented in the code, which means the degree of impact of refactoring is low.

There are some recommendations for improving modularity in a system

Break the system into several encapsulated elements.
Minimize connascence across encapsulated elements.
It is fine to maximize the connascence within the encapsulated element boundary as the consequence of the encapsulation and the minimization of cross-boundary connascence.

Comments

Increase of Malicious Activities and Implementation of reCaptcha

In recent time, I've seen the increase of malicious activities such as login attempts or phishing emails to some accounts I manage. Let me list some of them and the actions taken. SSH Access Attempts This happened on a server that host a Gitlab server. Because of this case, I started to limit the incoming traffic to the server using internal and cloud firewall provided by the cloud provider. I limit the exposed ports, connected network interfaces, and allowed protocols. Phishing Attempts This typically happened through email and messaging platform such as Whatsapp and Facebook Page messaging. The malicious actors tried to share a suspicious link lured as invoice, support ticket, or something else. Malicious links shared Spammy Bot The actors leverage one of public endpoint on my website to send emails. Actually, the emails won't be forwarded anywhere except to my own email so this just full my inbox. This bot is quite active, but I'm still not sure what...

Configuring Swap Memory on Ubuntu Using Ansible

If we maintain a Linux machine with a low memory capacity while we are required to run an application with high memory consumption, enabling swap memory is an option. Ansible can be utilized as a helper tool to automate the creation of swap memory. A swap file can be allocated in the available storage of the machine. The swap file then can be assigned as a swap memory. Firstly, we should prepare the inventory file. The following snippet is an example, you must provide your own configuration. [server] 192.168.1.2 [server:vars] ansible_user=root ansible_ssh_private_key_file=~/.ssh/id_rsa Secondly, we need to prepare the task file that contains not only the tasks but also some variables and connection information. For instance, we set /swapfile as the name of our swap file. We also set the swap memory size to 2GB and the swappiness level to 60. - hosts: server become: true vars: swap_vars: size: 2G swappiness: 60 For simplicity, we only check the...

Deliver SaaS According Twelve-Factor App

If you haven't heard of the twelve-factor app , it gives us a recommendation or a methodology for developing SaaS or web apps structured into twelve items. The recommendation has some connections with microservice architecture and cloud-native environments which become more popular today. We can learn the details on its website . In this post, we will do a quick review of the twelve points. One Codebase Multiple Deployment We should maintain only one codebase for our application even though the application may be deployed into multiple environments like development, staging, and production. Having multiple codebases will lead to any kinds of complicated issues. Explicitly State Dependencies All the dependencies for running our application should be stated in the project itself. Many programming languages have a kind of file that maintains a list of the dependencies like package.json in Node.js. We should also be aware of the dependencies related to the pla...

Kenshin VS The Assassin

It is an assassin versus assassin.

Handling PDF Generation in Web Service

If we are building a website that requires a PDF generation feature, there are several options for implementing it based on the use cases or user requirements. First, we can generate the PDF on the client side using any available client library. It is suitable if the use case is to print out some data that is already available inside certain website components, and we want to maintain the styles of the components in the document. Second, we can do it fully in the back-end using any library available, such as PDF-lib, jsPDF, and so on. This approach is suitable if we want to keep the data processing or any related business functions in the back-end server. This second approach might have disadvantages, such as the difficulty of maintaining the design assets and styles which are already on our website. Third, it is using a hybrid approach, where certain processes are handled on the client side, and some are handled on the back-end. In this post, I want to discuss more about the...

Free Cloud Services from UpCloud

Although I typically deploy my development environment or experimental services on UpCloud , I do not always stay updated on its announcements. Recently, I discovered that UpCloud has introduced a new plan called the Essentials plan, which enables certain cloud services to be deployed at no cost. The complimentary services are generally associated with network components or serve as the foundation for other cloud services. This feature is particularly useful when retaining foundational services, such as a load balancer, is necessary, while tearing down all services and reconfiguring the DNS and other application settings each time we temporarily clean up infrastructure to reduce costs is undesirable. When reviewing the service specifications of the cloud services in the Essentials plan, they appear to be very similar to those in the Development plan. The difference in service levels is unclear, but it could be related to hardware or resource allocation. For instance, the loa...

LUKI NOTES

Search This Blog