Architectural Design in Software Systems

Architectural Design

• Architectural design is about understanding how a software system is organized and designing its structure.
• It links design to requirements engineering.
• It identifies components and their relationships.
• The output is an architectural model describing the system.
• Architectural design is often done simultaneously with other specification work.

Agility and Architecture

• Agile processes often start with designing an overall system architecture.
• Incremental architecture development is often unsuccessful.
• System architecture refactoring is usually costly, impacting many components.

Packing Robot Control System Architecture

• The system has components like a vision system, object identification system, arm controller, gripper controller, packaging selection system, packaging system, and conveyor controller.
• The diagram shows how these components interact.

Architectural Abstraction

• Architectural design overlaps significantly with requirements engineering.
• Non-functional requirements greatly impact system architecture.
• Architectures can be designed at two levels:
  • Architecture in the small: Individual program's structure.
  • Architecture in the large: Complex enterprise systems are distributed across multiple (potentially different company) machines, encompassing multiple programs.

Advantages of Explicit Architecture

• Facilitates stakeholder communication, showing the system to reviewers.
• Enables system analysis, to verify functional and non-functional requirements (performance, reliability, maintainability).
• Aids in large-scale reuse, as a model of the system structure.

Architectural Representations

• Simple block diagrams are common, showing entities and relationships, with boxes for components and arrows for relationships.
• However, they lack semantics (no types or properties of entities).
• Box and line diagrams are helpful in communication with stakeholders/project planning.

Use of Architectural Models

• Facilitates discussion with stakeholders.
• They are used for documenting an architecture design (showing components, interfaces, connections).
• High-level architectural views are less cluttered and easier to understand than highly detailed ones.

Architectural Design Decisions

• Architectural design is a creative process where decisions are made about organization based on functional and non-functional requirements.
• There's no one-size-fits-all process; decisions depend on type of system, architect experience, and specific requirements.
• Common structural decisions significantly impact system development.

Architecture Reuse

• Systems with similar domains often have similar architectural structures.
• Application product lines frequently reuse core architectures with variants.
• Architectures can be based on patterns or "styles" (descriptions of system organization).

Architecture and System Characteristics

• Key characteristics of systems include performance/communication (localization/replication), security (inner layers protect critical data), safety (localize safety critical features), availability (redundancy), and maintainability (modular design).

Architectural Views

• Different views are created to document a complex system.
• Different notations are used to clearly depict different aspects.
• Different views display the system from different perspectives (design, implementation/process, physical deployment).

4 + 1 View Model of Software Architecture

• Models describe logical (components), process (runtime interaction), development (components), physical (deployment), and scenarios (use cases).

Representing Architectural Views

• UML is sometimes criticized for being insufficient for high-level system architecture.
• informal notations or Architectural Description Languages (ADLs) may be easier for high-level documentation.

Architectural Patterns

• Patterns are reusable designs, often summarized in tables and diagrams.
• Patterns provide design examples and help solve design issues common across different applications.

Model-View-Controller (MVC) Pattern

• This pattern is useful in situations where the data and presentation (Views) can change independently.
• Key components are the Model, which manages data; the View, which manages user interface; and the Controller, which handles user interaction.

Web Application Architecture Using MVC

• Illustrates a web client-server application using the MVC pattern.
• The diagram shows how user interaction flows though the components of the design.

Layered Architecture

• The system is modeled as layers of services.
• Each layer relies only on the layer beneath it, supporting independence.
• It simplifies the process since changes in a layer rarely impact others.
• Change and portability are supported (only adjacent layers are impacted by changes elsewhere.)

Repository Architecture

• A repository is a central point where components store and access data.
• Sub-systems may communicate by either sharing data in a repository (frequently used) or by passing it directly.

Client-Server Architecture

• This describes a system organized as servers providing services to requesting clients.
• Client-server systems are usually distributed across a network.
• The model emphasizes server-client separation (separate components).

Pipe and Filter Architecture

• Data flows through a sequence of transformations, with each component being a "filter".
• Data gets processed in steps until the desired output is produced.
• Suitable for batch-type processes.

The Pipe and Filter Patterns

• This pattern is one where the steps of a data transformation are handled by distinct components- "Filters".
• The steps of processing are designed into a pipeline.

Application Architectures

• Application systems are designed around business needs, and frequently share common architectures.
• A generic application architecture encapsulates common elements.
• These common structures/architectures are often adapted to new tasks, systems, or businesses.

Use of Application Architectures

• Application architectures are used as a foundation, checklist, organizational tool, and vocabulary for understanding.

Examples of Application Types

• Data processing (batch processing), Transaction processing (database updates), Event processing, and Language processing.

Transaction Processing Systems

• Transaction processing involves sequences of operations that are treated as atomic.
• Systems involving user input that changes database records, such as ATM transactions or order fulfillment.

Information Systems Architecture

• Information systems that interact with shared databases have certain characteristics.
• Often implemented as layered architectures to help separate functionality in the system (and to handle users).

This quiz covers the fundamentals of architectural design in software engineering. It explores system organization, component relationships, and the significance of architectural models. Additionally, it discusses the impact of agility on architecture and the specific architecture of a packing robot control system.