Notes

Software Architecture and Design - Goals, Principles plus some Key Considerations
Philippe Kruchten, Grady Booch, Kurt Bittner, and Rich Reitman derived and refined a definition of architecture predicated on work by Mary Shaw and David Garlan (Shaw and Garlan 1996). Their definition is:

"Software architecture encompasses the set of significant decisions about the organization of a software system like the selection of the structural elements and their interfaces by which the system is composed; behavior as specified in collaboration the type of elements; composition of these 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 something 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, ultimately, architecture boils Down to whatever the important stuff is."

Software application architecture may be the process of defining and coming up with a solution that's well structured and meets all the technical and operational requirements. The architecture will be able to consider and improve upon the common quality attributes such as for example performance, security, and manageability.

The main focus of the program architecture is how the major elements and components within an application are employed by, or connect to, other major elements and components within the application form. Selecting data structures and algorithms or the implementation details of individual components are design concerns, they're no architectural concerns but sometimes Design and Architecture concerns overlap.

Before starting the architecting of any software, there are a few basic questions that people should make an effort to get answers for. They are as follows:

How the users of the system will be interacting with the system?

How will the application be deployed into production and managed?

What are the various non-functional requirements for the application form, such as for example security, performance, concurrency, internationalization, and configuration?

How can the application be made to be flexible and maintainable as time passes?

Do you know the architectural trends that may impact your application now or after it has been deployed?

Goals of Software Architecture

Building the bridge between business requirements and technical requirements is the definitive goal of any software architecture. The goal of architecture is to identify the requirements that affect the essential structure of the application form. Good architecture reduces the business risks associated with building a technical solution while a good design is flexible enough in order to handle the changes which 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 performance and security), and the tradeoffs required to address user, system, and business requirements.

Principles of Software Architecture

The basic assumption of any architecture should be the belief that the look will evolve over time and that certain cannot know everything one have to know up front. The design will generally need to evolve through 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 some 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 ought to be identified and applied upfront.

Architects should consider using an incremental and iterative approach to refining their architecture. Focus on baseline architecture to have the big picture right, and evolve candidate architectures as you iteratively test and improve one's architecture. Usually do not try to get it fine the first time-design just as much as you can as a way to start testing the design against requirements and assumptions. Iteratively add details to the design over multiple passes to make certain that you get the big decisions right first, and focus on the details. A common pitfall is to dive into the details too quickly and get the big decisions wrong by making incorrect assumptions, or by failing to evaluate your architecture effectively.

When testing your architecture, think about the following questions:

What were the main assumptions that were made while architecting the system?

What are 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 place to mitigate key risks?

In what ways is this architecture an improvement over the baseline or the final candidate architecture?

Design Principles

When getting started with Software design, one should remember the proven principles and the principles that adheres to minimizes costs and maintenance requirements, and promotes usability and extensibility. The main element principles of any Software Design are:

Separation of concerns: The key factor to be kept in mind 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 responsible for just a specific feature or functionality.

Principle of Least Knowledge: A component 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 should be done of them costing only one place. It should never be repeated in a few other component or module

Minimize upfront design: This principle is also sometimes referred to as YAGNI ("You ain't gonna require it"). Design only what is necessary. Specifically for agile development, one can avoid big design upfront (BDUF). If the application form 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. If possible, use composition over inheritance when reusing functionality because inheritance increases the dependency between parent and child classes, thereby limiting the reuse of child classes. This reduces the inheritance hierarchies, that may become very difficult to deal with.

Set up 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 for example dependency analysis and static code analysis, during development

Not only development, also consider the operation of your application. Determine 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 a few key considerations that need to be kept in mind while doing that:

Separate the areas 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 exactly layers communicate with each other.

Abstraction should be used to implement loose coupling between layers.

Do not mix various kinds of components in the same logical layer. For instance, the UI layer should not contain business processing components, but instead should contain components used to handle user input and process user requests.

Keep carefully Provincetown architects within a layer or component.
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