8. Software Engineering

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Research vs Developing a Product

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Challenge 1: Quality

Stability

Modularity

Robustness

Flexibility

Flickr: sbisson

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Challenge 2: Time to market

Flickr: Kristian M

Effort Estimation

Effort vs Reward

Priorization

Often in direct conflict with quality

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Challenge 3: Changing requirements

Flickr: 416style

A new competitor

Customer feedback

A new technology

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Challenge 4: User Experience

Flickr: geoffeg

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Challenge 5: Efficient Teamwork

Flickr: royskeane

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Summary Challenges

QualityTime To Market

Changing Requirements

User Experience

Efficient Teamwork

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Running the project

QualityTime To Market

Changing Requirements

User Experience

Efficient Teamwork

Needed: a process that is

- Flexible (Changing Requirements)

- Quickly leads to results (Time to Market)

- Little overhead (Efficient teamwork)

- Shows problems early on (Time to Market and Quality)

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Traditional way of running software projects

waterfall model (image source: Wikipedia)

What if requirements change halfway through project?

What if unexpected issues arise?

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A better way to run software projects

Iteration 1

Iteration 2

Iteration 3

Do short iterations with all phases: iterative process

Examples:

- Scrum

- RUP (Rational Unified Process)

- ...

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http://www.youtube.com/watch?v=IyNPeTn8fpo

Scrum et al. (Google Tech Talk)Ken Schwaber

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Scrum

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Backlogs

Requirements written as “User Stories”

Example: “iPhone app user can log-in with username and password, in order to log history of requests”

Effort for each story is estimated (how, see later)

Prioritized list of stories in the Product Backlog. Re-prioritize regularly.

For each sprint, just select top-n stories to Sprint Backlog

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SprintsSprint = Iterations (2-4 weeks)

Meetings

Sprint Planning Meeting-> Team decides how much it can do in the Sprint (not the manager).Set a goal.

Daily Scrum15 minutes max (“timeboxed”). Each team member: What I am working on now? / what’s next? / problems?Check progress on burndown chart. If needed drop tasks.

Sprint Review Meeting

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NO INTERRUPTIONS DURING SPRINT

“People need uninterrupted time to get things done”

why??

http://gettingreal.37signals.com/ch07_Alone_Time.php

http://www.joelonsoftware.com/articles/fog0000000068.html

With programmers, it's especially hard. Productivity depends on being able to juggle a lot of little details in short term memory all at once

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Estimations

Product Backlog: Stories are estimated roughlyUnit: Story points. A measure of “size” / ”complexity”Ex 1: 0, ½, 1, 2, 3, 5, 8, 13, 20, 40, 100Ex 2: 0, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89

Team estimates using Planning Poker

Sprint Backlog: Each story gets assigned detailed tasks (in hours) at Sprint Planning

Longterm planning: velocity = story points / sprint“we need about 3 sprints to finish this module at our current velocity”

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Why a process at all? Why Scrum?

You need some process, otherwise you get lost. At the latest with more than 5 people more than 5 customers.

Scrum doesn’t get in the way. Simple. Lightweight. “Advanced common sense” *

Perfect for startups

* David Allen, in order to describe “Getting Things Done”

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Scrum is part of Agile

http://agilemanifesto.org/

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More Agile Practices (or: more common sense)

QualityTime To Market

Changing Requirements

User Experience

Efficient Teamwork

Testing / Test Driven Development

Code refactoring

Continuous Integration

Pair Programming

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If you don’t like Agile ...

http://www.joelonsoftware.com/articles/fog0000000043.html

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Consolidated must-haves

Source control (no-brainer) Subversion: http://subversion.tigris.org/Git: http://git-scm.com/

Automated TestingGoogle Test (http://code.google.com/p/googletest/)Often part of good frameworks (e.g. Rails)

Continuous IntegrationAutomated daily builds

CDash http://www.cdash.org/Cruise Control http://cruisecontrolrb.thoughtworks.com/ (Ruby only)

Hallway Usability TestingJust give your product to a few random people (in person) and observe them using it (before release)

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On Deployment- We have 20 million items indexed. Need multiple machines to keep index- What if we have many requests, so we need to replicate the whole system

- Buying and maintaining so much hardware is expensive

Amazon Web Services (“Cloud Computing”) to the rescue

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On Outsourcing Work

Do not outsource core competence

Overhead from time difference, communication, project management over distance, travel

Graphic design, administration etc. are things to outsource first (www.elance.com)

What is special about Vision?In Terms of Engineering

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What’s special about Vision (Consumer)

Software is a lot harder to do than e.g. a web-community in PHP (means you need more money also)

Lot’s of uncertainty and complexity

Still early stage of technology

Hard to find good specialists

How we did it

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How we did it

- Two Scrum-Teams in parallel - Use of Story points- 3-week sprints- 2-day break between sprints

Ec2, Trac + Agilo, C++, Rails, Googletest, SVN, CDash, Reviewboard

In-house: Vision, Rails, iPhoneOutsourced: Android, Symbian etc.

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Challenges we still face

User stories for system related topics

Uncertainty in Computer Vision related stories/tasks

Testing can still be improved

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Polar Rose: How we did it

- Two teams (infrastructure and vision) - Sys admin & dedicated Q/A tester- 2-3 week sprints- daily and weekly standup Skype meetings

Ec2, S3, C++, Python Java, Jira, Confluence, WordPressSVN, Bamboo

In-house: Vision, Infrastructure, Web, iPhone/iPad, Androidoutsourced: Symbian, small projects/prototypes

Q & A

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Resources IIKen Schwaber Scrum http://www.youtube.com/watch?v=IyNPeTn8fpo

Agile Manifesto http://agilemanifesto.org/

The Joel Testhttp://www.joelonsoftware.com/articles/fog0000000043.html

Wikipedia: Scrum http://en.wikipedia.org/wiki/Scrum_(development)

Wikipedia: Planning Poker http://en.wikipedia.org/wiki/Planning_poker