Introduction
Software architecture is a fundamental aspect of software engineering that describes how a system is structured and organized. It involves high-level decisions about the organization of a software system which determines how it will be implemented through low-level design and coding. Choosing an appropriate software architecture is critical for developing quality systems that meet requirements and are easy to maintain.
This research paper will explore different aspects of software architecture through a review of relevant literature. It aims to provide an overview of key concepts, principles, and processes involved in software architecture design. Some questions that will be addressed include: What is software architecture and why is it important? What are common architectural styles and patterns? How does architecture support requirements, quality attributes and system evolution? What challenges are involved in creating architectures and how can they be evaluated?
The paper will summarize published works on these topics to help gain a deeper understanding of software architecture. It is intended to serve as a reference for researchers and practitioners seeking to learn more about this fundamental aspect of software development. Well-designed architecture lays the foundation for successful systems, so this research will help illuminate best practices and approaches.
Software Architecture – Definition and Importance
Before delving into specific aspects of software architecture, it is important to have a clear definition and understand why it matters. Bass et al. (2003) provide a commonly cited definition: “the software architecture of a program or computing system is the structure or structures of the system, which comprise software components, the externally visible properties of those components, and the relationships among them.” In essence, the architecture defines the overall system composition and flow.
Several researchers have emphasized the high importance of architecture in software development. Garlan and Shaw (1993) note that architecture captures critical early design decisions that have a major impact on all downstream development activities like design, implementation, maintenance and evolution. A key goal of architecture is to partition the system into components that can be developed and maintained independently, while ensuring overall integrity (Bass et al., 2003). Architecture needs to balance functional requirements with important quality attributes like performance, security, usability and more.
If architectural decisions are not made effectively up front, it can lead to significant issues later like inflexibility, poor modifiability, high maintenance costs and inability to meet new requirements (Lassing et al., 2002). This underscores why architecture deserves attention from the very start of a project. Overall system structure, decomposition, interfaces – these architectural aspects must carefully address business needs and technical constraints. Once development begins, it becomes much more difficult and costly to refactor and change architecture.
Common Architectural Styles and Patterns
With an understanding of the importance of architecture, it is useful to examine some typical architectural styles that are commonly employed. Each style addresses different priorities, so choosing the right one depends on project goals and quality requirements.
Layered architectural is a common style used frequently (Buschmann et al., 1996). It partitions the system into distinct layers, such as a presentation layer, application layer and data layer. Each layer uses the services of the layer below and provides services to the layer above. This improves modularity, promotes information hiding and separate development of layers.
Other popular styles include:
Pipes and Filters: Components communicate via pipes that pass data. Used when incremental processing is important.
Client-Server: Central server provides services to clients. Good for distributed apps requiring centralized coordination.
Shared Repository: Central database provides data access for components. Simplifies adding/removing components.
Model-View-Controller (MVC): Separates representation from business logic and user input handling. Benefits for web and GUI applications.
Several architectural patterns have also emerged as useful solutions for common problems like Singleton, Facade, Observer, Adapter and more (Buschmann et al., 1996). These capture structured approaches that have been shown to work well for specific tasks. Architects can leverage patterns to reuse proven best practices.
Architectural styles and patterns help solve domain-specific quality concerns and provide structure to a complex system. By choosing the right approach based on the project context, architecture helps achieve non-functional requirements.
Supporting Requirements and Quality Attributes
Software architecture must explicitly address functional requirements as dictated by the problem domain and stakeholder needs. Equally important is aligning the architecture to support key quality attributes like performance, security, modifiability, testability and many others (Bass et al., 2003).
Multiple quality attributes should be considered simultaneously as trade-offs may exist. For example, a highly optimized structure for performance may compromise modifiability. Architecture Evaluation Method (ARM) is a popular technique proposed by a MIT research group to analyze alternative architectural approaches against quality goals (Kazman et al., 2000). It assesses things like changeability impact, interface simplicity and other forces.
Other techniques like Architecture Tradeoff Analysis Method (ATAM) involve stakeholders to identify architectural approaches best suited to conflicting quality concerns (Clements et al., 2002). Goals like maximizing modularity may need to be balanced against performance needs, and assessing different architectural choices helps make informed compromises.
Ultimately, during iterative system analysis and development, functional requirements continue to evolve and new ones emerge. Architecture must support ongoing changes and evaluation throughout development lifecycle (Kazman et al., 2000). Rigorous quality attribute analysis at the architecture level reduces rework needed to meet evolving needs.
Enabling System Evolution
A well-designed software architecture should lay the foundation for system evolution and continuous change, both anticipated and unanticipated. Modifiability is one of the top characteristics affecting software quality and costs, so architects must emphasize change readiness (Lehman and Belady, 1985).
Some strategies that promote architectural evolution over time are:
Minimize dependencies between components to enable independent development.
Architect for pluggability so new capabilities can be added without major changes.
Segregate architecture into layers or subsystems around stable cores and variable shells.
Analyze how new capabilities or quality attribute changes may impact architecture.
Use design patterns and architectural styles that inherently facilitate upgrades.
Model and simulate changes to understand impacts and evaluate options.
Prepare documentation to help new developers understand the system.
Perform architecture reviews and refactoring as needed to maintain flexibility.
While aiming for “evolutionary architects” is idealistic given project constraints, consciously architecting for change contributes significantly to long-term success (Bosch, 2000). Flexibility should guide design decisions as much as initial requirements.
Challenges and Evaluation
Selecting the right architectural approach involves significant challenges for various reasons. Stakeholder requirements are often unclear, quality attributes are difficult to quantify, and technical issues remain unresolved early on (Tang et al., 2007). Other challenges arise from things like team inexperience, schedule pressures and inability to foresee future changes.
Careful architecture evaluation is thus critical to select a high-quality solution. In addition to ARM and ATAM techniques, other methods exist:
Architecture reconstruction infers design from code to evaluate decisions.
Architecture conformance checks if implementation matches intention.
Architecture trade study compares alternatives by prototype or modeling.
Architecture backtalk gathers feedback to continually refine decisions.
Architecture walkthrough involves designers presenting and defending ideas.
Active evaluation throughout the project aids architecture communication and refinement. It exposes risks to be addressed through further analysis or mitigation strategies. With challenges inherent in architectural design, evaluation plays an important role in developing robust, evolvable systems.
Conclusion
Software architecture serves as the blueprint for any complex system and its importance cannot be overstated. This research paper provided an overview of key topics in architecture including core definitions, common styles and patterns, requirements mapping, quality attribute consideration, evolution support, and evaluation challenges. References were made to significant published works to summarize current research perspectives.
The multidimensional aspects of architecture design require balancing technical factors with business drivers. Iterative analysis, modeling, prototyping and evaluation help manage risks and improve decisions. With well-established architectural principles and techniques available, addressing architecture conscientiously from the start sets projects up for greater success, stability and change readiness over the long run. Future work could explore architecture in specific technical domains or compare methodologies in more depth. Overall, a strong foundation in software architecture forms the basis for developing robust, maintainable systems.
Andrew Stroud