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 set of significant decisions concerning the organization of a software system including the selection of the structural elements and their interfaces by which 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 something into its parts; the decisions which are Hard to change; you can find multiple architectures in a system; what is architecturally Significant can transform over a system's lifetime; and, ultimately, architecture boils Down to regardless of the important stuff is. Software application architecture may be the process of defining and coming up with a solution that is well structured and meets all of the technical and operational requirements. The architecture will be able to take into account and improve upon the common quality attributes such as performance, security, and manageability. The main focus of the Software architecture is the way the major elements and components in a application are employed by, or connect to, other major elements and components within the application. Selecting data structures and algorithms or the implementation information on individual components are design concerns, they are not an architectural concerns but sometimes Design and Architecture concerns overlap. Prior to starting the architecting of any software, there are a few basic questions that we should make an effort to get answers for. They're as follows: How the users of the machine will be interacting with the machine? How will the application be deployed into production and managed? Do you know the various non-functional requirements for the application, such as for example security, performance, concurrency, internationalization, and configuration? How can the application be designed to be flexible and maintainable as time passes? What are the architectural trends that may impact the application now or after it has been deployed? Goals of Software Architecture Building the bridge between business requirements and technical requirements is the main goal of any software architecture. The goal of architecture is to identify the requirements that affect the basic structure of the application. Good architecture reduces the business risks associated with building a technical solution while a good design is flexible enough to handle the changes which will occur over time in hardware and software technology, in addition to 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 necessary to address user, system, and business requirements. Principles of Software Architecture The essential assumption of any architecture should be the belief that the design will evolve as time passes and that one cannot know everything one need to know up front. The look will generally need 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 try to list down a few of the Architectural principles: The system should be built to change rather than building to last. Model the architecture to investigate 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 approach to refining their architecture. Start with baseline architecture to obtain the big picture right, and then evolve candidate architectures as one iteratively test and improve one's architecture. Usually 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 design over multiple passes to make sure that you get the big decisions right first, and then focus on the details. A common pitfall is to dive in to the details too quickly and obtain the big decisions wrong by making incorrect assumptions, or by failing woefully to evaluate your architecture effectively. When testing your architecture, consider 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? What are the key risks with this architectural approach? What countermeasures are in spot 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 keep in mind 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 considered is minimization of interaction points between independent feature sets to accomplish high cohesion and low coupling. Single Responsibility principle: Each component or module should be independent in itself and responsible for only a specific feature or functionality. Principle of Least Knowledge: A component or object should not know about internal information on other components or objects. Don't repeat yourself (DRY): The intent or implementation of any feature or functionality should be done at only one place. It will never be repeated in some other component or module Minimize upfront design: This principle can be sometimes known as YAGNI (You ain't gonna need it). Design only what's necessary. Especially for agile development, you can avoid big design upfront (BDUF). If the application requirements are unclear, or when there is a possibility of the look evolving over time, one should avoid making a large design effort prematurely. Design Practices Keep design patterns consistent within each layer. Do not duplicate functionality in a 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 also reduces the inheritance hierarchies, that may become very difficult to cope 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 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 needed by the IT infrastructure to ensure the efficient deployment and operation of your application. Application Layers: While architecting and designing the system, 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 considered 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 that a feature or functionality can be optimized independently of other features or functionality Be explicit about how layers communicate with one another. Abstraction ought to be used to implement loose coupling between layers. Do not mix various kinds of components in exactly the same logical layer. For example, 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. Long Island architects
Long Island architects
