SENG 350 - Software Architecture & Design

Introductions

I am Neil Ernst,

  • acting director of the Software Engineering program,
  • associate professor in the Department of CS,
  • formerly a senior researcher and consultant at the Software Engineering Institute.
  • I’ve approached software architecture from both an academic/research perspective, as well as a consulting engineer.
  • In my four years at the SEI, I helped evaluate, document, and design software architectures in government and scientific settings.

Learning Outcomes

  • Apply software patterns and architectural styles to solve design problems
  • Understand the value of quality attributes and scenarios in testing potential designs
  • Analyse architectural approaches using rigorous techniques
  • Understand what decisions are the architecturally significant decisions.

Learning Outcomes

  • Understand the relevance of languages and notations, including the UML, for abstracting design models.
  • Apply Generative AI techniques for designing, building, and deploying software systems.
  • Leverage tools and techniques for working on large collaborative projects with colleagues.

Course Mechanics and Outline

Course Overview

This course looks at Software Architecture and Design.

In my experience there is a key problem with that title.

You have only done a few years of software development. Some of the problems in software architecture take years of practice to appreciate.

Can you think of some?

Poll 2: How much of software is about writing code?

Learning about software architecture and design has two main approaches.

One Documenting and Designing is to prepare you to prepare and describe architectures you will be responsible for.

For example, you move into a government IT job. You are asked to prepare an IT modernization strategy for the Ministry of Finance. You will present that strategy to senior leaders who want to know the technical and non-technical details about your plan.

The second objective Understanding and Refactoring is to enable you to work on the opposite side. Given a software system, come up with intelligent questions and analysis to understand a) how it works b) what key requirements it satisfies c) what evidence supports that.

A contractor presents their finely polished powerpoint deck for their bid to modernize your company’s payroll with a custom one. You need to know a) what it integrates with in your system b) how security guarantees can be met c) long-term costs.

Project

Outline

The main deliverable in this course is a major, term-long project you will do with 4-5 other students.

Fill out the survey at https://ca.research.net/r/R3FCBMG

We will then allocate teams based on compatibility.

Project Goal

  • The overall goal of the project is to design, implement, and refactor the architecture, architectural choices, and abstractions of a moderately large web application.
  • Your individual project mark will reflect your team’s performance, adjusted by a peer / instructor participation factor. If you do nothing, you can expect a 0 for the project (and will fail the course).
  • We will go into detail about functioning well in groups, but you should not assume that your group’s problems will be an excuse for poor performance.

Project Schedule

Software Architecture - What Is It?

Definitions

Here are three definitions.

  1. “the important stuff … whatever that is (Martin Fowler)”
  2. “Architecture is the decisions that you wish you could get right early in a project.” Ralph Johnson
  3. the “…significant design decisions (where significant is measured by the cost of change).” (Grady Booch)

Our definition

Here is the definition we will use. It is designed to orient us to the notion that there is not just one thing to call the architecture, but rather a set of structures that help us reason about what the system is doing.

The software architecture of a system is the set of structures needed to reason about the system, which comprise the software elements, relations among them, and properties of both. (text p.4)

Motivating Software Architecture

The Problem

You don’t need structure when your files are small enough. But we pretty quickly exceeded that…

Margaret Hamilton, lead engineer for the NASA Apollo software

images from Garlan and Shaw, “Software Architecture: Perspectives…” 1996

Summary and Next Time

We’ve started to expand on what architecture is in the context of software engineering.

On Thursday we will start to go into detail about how we define these structures, and how we uncover them.