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Defining Software Architecture: Principles, Decisions, and Documentation

 

Introduction

Software architecture serves as the foundation for designing complex systems, ensuring scalability, maintainability, and performance. A well-defined architecture aligns technical solutions with business goals while addressing constraints and trade-offs. This document explores key principles, decision-making processes, and documentation approaches for defining effective software architecture.

Basic Principles of Software Architecture

1. Identify Architectural Drivers

Architectural drivers include functional requirements, quality attributes, and constraints such as performance expectations, security policies, budget, and schedule. Understanding these drivers ensures that the architecture aligns with the system's goals.

2. Define the Architectural Strategy

Establish the system’s structuring approach by considering architectural styles (e.g., layered, microservices, event-driven) and design patterns (e.g., MVC, CQRS). A well-defined strategy ensures modularity, maintainability, and adaptability.

3. Perform Trade-Off Analysis

Prioritize quality attributes such as scalability, security, and maintainability. Apply methodologies like the Architecture Tradeoff Analysis Method (ATAM) or Cost-Benefit Analysis to evaluate different design options and balance trade-offs.

Architect's Priorities

1. Functional Requirements

  • Define architecturally significant requirements that impact design decisions.

  • Conduct a Build vs. Buy analysis to assess time-to-market and cost constraints.

2. Non-Functional Requirements (NFRs)

  • Ensure critical attributes such as scalability, security, availability, compliance, and performance.

3. Constraints & Trade-offs

  • Consider constraints including budget, available skill sets, and technology stack compatibility.

  • Optimize cost while maintaining essential quality attributes.

4. Vendor Lock-in Considerations

  • Evaluate risks associated with proprietary platforms or cloud providers.

  • Balance time-to-market benefits against long-term flexibility.

Decision-Making in Software Architecture

Several methodologies guide architects in making informed choices based on architectural drivers and trade-offs:

1. Attribute-Driven Design (ADD)

  • Developed by SEI, ADD focuses on tactics and patterns to achieve quality attributes.

  • Uses an iterative process where architectural drivers define the solution space.

2. Siemens’ Four View Model (S4V)

  • Defines architecture using four perspectives:

    • Conceptual View – High-level abstractions

    • Execution View – Runtime behavior

    • Module View – Structural organization

    • Code View – Implementation details

3. Rational Unified Process (RUP)

  • Focuses on use cases, non-functional requirements, and risks.

  • Defines architecture through technical decisions and iterative refinements.

Documenting Software Architecture

A well-documented architecture ensures effective communication among stakeholders and serves as a reference for future enhancements. Several industry-standard models exist to represent architectural views.

Comparison of Architectural Documentation Models

ModelFocusViews Included
C4 ModelHierarchical system modelingContext, Container, Component, Code
4+1 ModelStakeholder-centric representationLogical, Process, Development, Physical, Use Case
Siemens S4VMulti-perspective designConceptual, Execution, Module, Code
SEI ViewsSoftware system organizationModule, Component & Connector, Allocation
Rational ADSRational Unified Process ApproachRequirements, Design, Realization, Verification

The 4+1 Model of Software Architecture

Initially proposed by Philippe Kruchten, the 4+1 model organizes architecture into five key views, originally using Booch notation (pre-UML era). The five views include:

  1. Logical View – Defines system components and their relationships using object-oriented modeling.

  2. Process View – Represents concurrency, synchronization, and inter-process communication.

  3. Development View – Shows how software components are organized in source code repositories.

  4. Physical View – Maps software components to hardware nodes and infrastructure.

  5. Use Case View – Illustrates system behavior from the end-user perspective.

UML & Software Modeling

Several UML diagrams are used for architectural representation:

  • Structural Diagrams: Class, Object, Component, Deployment

  • Behavioral Diagrams: Use Case, Sequence, Activity, State

  • Data Flow & Business Process Diagrams

Before UML standardization, early software architecture documentation relied on Booch notations. UML provides a unified language for system modeling and communication.

Cloud & Modern Architectural Trends

Modern architecture incorporates:

  • Microservices & Event-Driven Architecture (Kafka, Event Sourcing)

  • Serverless Computing (AWS Lambda, Azure Functions)

  • Edge Computing (IoT, real-time processing)

  • AI/ML-based Architectural Considerations (Data pipelines, model serving infrastructure)

Deployment & DevOps Considerations

1. DevOps Integration

  • Implement CI/CD for continuous deployment.

  • Utilize monitoring and observability tools (Prometheus, Grafana).

2. Cloud Deployment Strategies

  • Use Blue-Green, Canary, or Rolling Updates for seamless deployments.

3. Containerization & Orchestration

  • Leverage Docker, Kubernetes, and Helm for scalable deployments.

Conclusion

Defining software architecture involves balancing multiple trade-offs while ensuring alignment with business goals. A well-documented and structured approach improves system scalability, maintainability, and adaptability. By following established methodologies, considering modern trends, and integrating DevOps practices, architects can design resilient and future-proof systems.


Interesting resources

Interesting resources

https://www.nasa.gov/pdf/637608main_day_2-david_garlan.pdf

https://biking.michael-simons.eu/docs/index.html

https://github.com/arc42

https://docs.arc42.org/home/

https://arc42.org/overview/

https://arc42.org/download

https://resources.sei.cmu.edu/library/asset-view.cfm?assetID=513862

(Views and beyond SEI CMU Template for SAD)

http://www.iso-architecture.org/42010/

http://www.iso-architecture.org/42010/templates/

https://resources.sei.cmu.edu/asset_files/TechnicalNote/2005_004_001_14498.pdf

(Comparison of Views & beyond template and ANSI-IEEE 1471-2000)

https://resources.sei.cmu.edu/asset_files/TechnicalNote/2003_004_001_14171.pdf

(Documenting Software Architecture in an Agile world)

http://www.iso-architecture.org/42010/cm/

(Conceptual model))

http://www.iso-architecture.org/42010/afs/

http://www.iso-architecture.org/42010/afs/frameworks-table.html

(Architecture frameworks table listing various frameworks)

Blown out TOGAF 7 diagram

https://i0.wp.com/tephramiriamcommunications.com/wp-content/uploads/2016/01/blowout.gif?ssl=1

https://slideplayer.com/slide/4267592/

To corelate where does Software Engineering Diagrams fit in to EA as per TOGAF please see this url:

https://pubs.opengroup.org/architecture/togaf9-doc/arch/chap31.html

To learn examples for Togaf modeling this site has interesting stuff:

https://www.togaf-modeling.org/ 

Togaf diagrams at visual paradigm:

https://circle.visual-paradigm.com/docs/togaf-adm-guide-through/phase-c-information-systems-architectures/how-to-develop-architecture-definition-document/ 

http://metasun.blogspot.com/2018/02/togaf-diagram-examples.html 

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