Conceptual and Concrete Architecture Linux Case Study Conceptual - - PowerPoint PPT Presentation

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Conceptual and Concrete Architecture Linux Case Study Conceptual - - PowerPoint PPT Presentation

Apr 12, 2023 226 likes •456 views

Conceptual and Concrete Architecture Linux Case Study Conceptual Architecture Intent direct attention at an appropriate decomposition of the system without delving into the details of interface specification [1]

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Conceptual and Concrete Architecture

“Linux Case Study”

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Conceptual Architecture

Intent

  • “ direct attention at an appropriate decomposition of the

system without delving into the details of interface specification”[1]

  • appropriate decomposition

– focus on key constructs & abstractions rather than on technical

details

[1] R. Malan, D. Bredemeyer, Software Architecture Action Guide.

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Conceptual Architecture

Includes

  • what a system does (functionality)
  • identification of significant components & connectors

– component responsibilities – component interactions – control & data flow

  • architectural (non-functional) mechanism

– e.g. security – other crosscutting concerns

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Conceptual Architecture

Provides

  • communicating architectural details with

– stakeholders (technical & non-technical)

Input artifacts

  • reference architecture (more on this later)
  • requirements (functional & non-functional)
  • documentation & code
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Conceptual

Activities

  • capturing system functionality

– requirements to use case descriptions

  • capture system properties

– evolution, system load, portability

  • capture system constraints

– legacy components, third party components – resources, time, – technical capabilities

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Concrete Architecture

Intent

  • implementation specific architecture

– decomposition into (implementation specific components) – identification of actual relationships

  • actual

– e.g. identify third party, COTS components

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Architectural Drift & Erosion

Architectural erosion

– conceptual architectural violations

Architectural drift

– concrete architecture shifts away from conceptual architecture – technical details need to be flushed out here

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Concrete Architecture

Includes

  • what a system does (functionality)
  • how will it do it (implementation)
  • identification of significant components & connectors

– component responsibilities – component interactions – control & data flow

  • realization of architectural (non-functional) mechanisms
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Concrete Architecture

Input Artifacts

  • ask the class
  • can we extract concrete architecture from code

– isn't that reveres engineering? – choice of tools

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Example

Linux

  • lack of formal architecture

– conceptual or concrete

  • considerable code size
  • fragmented documentation

– individual systems well defined but not the overall

  • based on

– Linux as a Case Study: Its Extracted Software Architecture,

Ivan T. Bowman, Richard C. Holt, Neil V. Brewster, 2005

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Linux Conceptual Architecture

Input artifacts

  • Unix & Minix descriptions
  • Linux documentation

seven kernel sub-systems

  • memory management

depends on file system for swapping

  • initialization depends on all
  • library sub system forms

the core

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Linux Conceptual Architecture

File Subsystem

  • data abstraction

architectural style

  • facade pattern

– virtual file system – system call interface

  • coupling & dependency

– support various hardware

devices

– logical file system formats

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Extraction of Concrete Architecture

LSEdit

  • Ian Davis guest presentation on May 17, 2010

General technique

  • inspection

– source (directory structures, packages, file naming etc) – compiled artifacts

  • clustering

– grouping of components

  • discovery

– inter-component dependency

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Linux Concrete Architecture

Observations

  • same subsystem

decomposition as conceptual arch

  • what happened to

dependency relationships?

– 19 vs 37 out of 42

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Dependency at a Glance

Conceptual Architecture Concrete Architecture

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Linux Concrete Architecture

Dependencies explained

  • “avoided existing interfaces for better efficiency”
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Linux Concrete Architecture

File Subsystem

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Linux Conceptual Architecture

Dependencies under a microscope

  • network interface subsystem on logical file subsystem

– SMBFS & NCPFS

  • network interface calls functions from the file subsystem
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Linux Conceptual Architecture

Dependencies under a microscope

  • process scheduler on device driver subsystem

– printk to print messages to the console – printk makes a call to device driver routine

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Linux Conceptual Architecture

Dependencies under a microscope

  • all file subsystem depends on IPC

– IPC subsystem implements reusable

synchronization primitives, used globally

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Conceptual Vs. Concrete

Comparisons

  • subsystem discovery pretty accurate

– despite different input artifacts

  • concrete architecture has more inter-component

dependencies

– architectural erosion and drift

  • violations

– in the name of to improvements (performance)