Philippe Kruchten, Grady Booch, Kurt Bittner, and Rich Reitman derived and refined a definition of architecture based on work by Mary Shaw and David Garlan (Shaw and Garlan 1996). Their definition is:
“Software architecture encompasses the group of significant decisions concerning the organization of a software system like the selection of the structural elements and their interfaces where the system is made up; behavior as specified in collaboration among those elements; composition of the structural and behavioral elements into larger subsystems; and an architectural style that guides this organization. Software architecture also involves functionality, usability, resilience, performance, reuse, comprehensibility, economic and technology constraints, tradeoffs and aesthetic concerns.”
In Patterns of Enterprise Application Architecture, Martin Fowler outlines some common recurring themes when explaining architecture. He identifies these themes as:
“The highest-level breakdown of a system into its parts; the decisions that are Hard to change; you can find multiple architectures in a system; what is architecturally Significant can change over a system’s lifetime; and, in the end, architecture boils Down to whatever the important stuff is.”
Software application architecture is the process of defining and creating a solution that’s well structured and meets all of the technical and operational requirements. The architecture should be able to take into account and improve upon the normal quality attributes such as performance, security, and manageability.
The main focus of the program architecture is how the major elements and components in a application are used by, or connect to, other major elements and components within the application. Selecting data structures and algorithms or the implementation details of individual components are design concerns, they are no architectural concerns but sometimes Design and Architecture concerns overlap.
Prior to starting the architecting of any software, there are a few basic questions that people should strive to get answers for. They’re as follows:
How the users of the system will be interacting with the machine?
How will the application be deployed into production and managed?
What are the various non-functional requirements for the application, such as security, performance, concurrency, internationalization, and configuration?
How can the application be designed to be flexible and maintainable as time passes?
Do you know the architectural trends that may impact your application now or after it’s been deployed?
Goals of Software Architecture
Building the bridge between business requirements and technical requirements may be the main goal of any software architecture. The purpose of architecture is to identify certain requirements that affect the basic structure of the application form. Good architecture reduces the business enterprise risks associated with creating a technical solution while an excellent design is flexible enough to handle the changes that will occur as time passes in hardware and software technology, as well as in user scenarios and requirements. An architect must think about the overall effect of design decisions, the inherent tradeoffs between quality attributes (such as for example performance and security), and the tradeoffs necessary to address user, system, and business requirements.
Principles of Software Architecture
The basic assumption of any architecture should be the belief that the design will evolve over time and that certain cannot know everything one need to know up front. The design will generally have to evolve during the implementation stages of the application as one learn more, so when one tests the look against real world requirements.
Keeping the above statement in mind, let’s make an effort to list down a few of the Architectural principles:
The system should be created to change instead of building to last.
Model the architecture to analyze and reduce risk.
Use models and visualizations as a communication and collaboration tool.
The key engineering decisions should be identified and applied upfront.
Architects should consider using an incremental and iterative method of refining their architecture. Start with baseline architecture to have the big picture right, and evolve candidate architectures as one iteratively ensure that you improve one’s architecture. Do not try to get it all right the first time-design as much as you can so as to start testing the design against requirements and assumptions. Iteratively add details to the look over multiple passes to be sure that you obtain the big decisions right first, and focus on the details. A common pitfall is to dive in to the details too quickly and get the big decisions wrong by making incorrect assumptions, or by failing woefully to evaluate your architecture effectively.
When testing contemporary houses , consider the following questions:
What were the primary assumptions that were made while architecting the machine?
Do you know the requirements both explicit and implicit this architecture is satisfying?
Do you know the key risks with this particular architectural approach?
What countermeasures are in spot to mitigate key risks?
In what ways is this architecture an improvement over the baseline or the last candidate architecture?
Design Principles
When getting started with Software design, one should keep in mind the proven principles and the principles that adheres to minimizes costs and maintenance requirements, and promotes usability and extensibility. The key principles of any Software Design are:
Separation of concerns: The key factor to be considered is minimization of interaction points between independent feature sets to accomplish high cohesion and low coupling.
Single Responsibility principle: Each component or module ought to be independent in itself and in charge of only a specific feature or functionality.
Principle of Least Knowledge: An element or object should not know about internal details of other components or objects.
Don’t repeat yourself (DRY): The intent or implementation of any feature or functionality ought to be done at only one place. It should never be repeated in a few other component or module
Minimize upfront design: This principle can be sometimes known as YAGNI (“You ain’t gonna require it”). Design only what is necessary. Especially for agile development, you can avoid big design upfront (BDUF). If the application requirements are unclear, or if you have a possibility of the design evolving over time, you need to avoid creating a large design effort prematurely.
Design Practices
Keep design patterns consistent within each layer.
Do not duplicate functionality within an application.
Prefer composition to inheritance. When possible, use composition over inheritance when reusing functionality because inheritance escalates the dependency between parent and child classes, thereby limiting the reuse of child classes. This reduces the inheritance hierarchies, which can become very difficult to deal with.
Establish a coding style and naming convention for development.
Maintain system quality using automated QA techniques during development. Use unit testing along with other automated Quality Analysis techniques, such as dependency analysis and static code analysis, during development
Not only development, also consider the operation of your application. Know what metrics and operational data are required by the IT infrastructure to ensure the efficient deployment and operation of one’s application.
Application Layers: While architecting and designing the machine, one needs to carefully think about the various layers into which the application will be divided. There are some key considerations that need to be kept in mind while doing that:
Separate the regions of concern. Break your application into distinct features that overlap in functionality as little as possible. The advantage of this approach is a feature or functionality can be optimized independently of other features or functionality
Be explicit about how layers communicate with one another.
Abstraction should be used to implement loose coupling between layers.
Do not mix different types of components in exactly the same logical layer. For instance, the UI layer shouldn’t contain business processing components, but instead should contain components used to handle user input and process user requests.
Keep the data format consistent inside a layer or component.