November 18, 2009

QCon 2009: Architecture Reviews

Rebecca Wirfs-Brock

  • Writer, reviewer of many different types of arch
  • How can you present your own arch well?

To explain:

  • what is your design? why is it good?
  • why did you make certain design decisions?

"Collaborate" definitions:

  1. work together, joint effort
  2. cooporate treasonably
    • which group will you be presenting to? what subgroups might there be? you MUST be aware of this, because strategy varies a lot

"Illusion of transparency" -- geeks are bad b/c we assume people know what's in our head, how we got to the conclusions we did;

  • works the other way too: bad at assuming we know what someone else is thinking

"In-group bias" -- if you're in my tribe you get afree pass

Book "Software Systems Architecture" by Rozonski et al; how to present architecture (nb: RWB thinks it's too defensive)

  • Decision
  • Constraints
  • Alternatives: what you considered and ruled out
  • Effects: what does decision imply
  • Evidence: here's why it's good
    • Leaves them on high note...

Instead, proactive, explaining + constructive; idea and goal is to open up discussion

  • Design idea
  • Requirements
  • Positives
  • Negatives
  • Limitations
  • Design notes
  • Issues, uncertainties

On giving advice: "triage" mentality focuses effort; don't focus on stuff that's irretrievably broken, or just on slightly scratched items

Key findings:

  • Recommendations: feel really strongly about
  • Suggestions: useful, but not wed to them
  • Observations: might lead you to other conclusions not necessarily explicit
  • Ground all in facts as much as possible
  • Be sure to comment on good ideas/decisions too! Gives you cred
  • Scale the review to the size and criticality of the project, and whether it's early or late in the process

Agile has architectural impacts

  • Does it support automation of acceptance tests
  • How can domain rules be encoded to be testable?
  • Ease of configuring? Reconfiguring?
  • Delivered and deployed incrementally?

Develop features (tracer bullets) that touch multiple parts of the system so you can exercise

Beware the technical stack; watch out for people who focus on low level technical elegance; (CMW: I am... occasionally guilty of this)

Merging existing systems (like product lines) is REALLY hard!

  • hidden requirements in developer heads, code
  • what's your migration strategy?

(CMW: this is like large scale, deep context switching)

Risks compound: do not underestimate; even if no single risk is big the cumulative effect can be huge.

Ensure right people are involved. Sometimes tribes don't talk, or are unsure of trade-offs.

Questions for reviewers:

  • Can focus some questions for different reviewers, along with some for all.
  • Are your questions yes/no? (aka, open/closed) do they lead to discussion or decision? (which do you want?)
    • gives columbo example here, funny visualizations in my head...
  • Some other types of questions:
    • evaluation (how good do you think...?)
    • accuracy (how did you come up with numbers...?)
    • completeness (is that all...?)
    • relevance (does this apply...?)
    • purpose (why did you suggest...?)
    • extension (tell me more about...)
  • No response in meeting? How long to wait? Bob Powers says "count to 9..."
  • Clarifying questions:
    • why do you say that...?
    • what exactly do you mean by...?
    • how does this relate to...?

Handling criticism, different types:

  • valid/invalid
  • aesthetics
  • judgemental
  • complexity
  • personal
  • "great!" (code for: "they didn't really look at it...")

(she has a paper on her website about criticism types)

Disagreement hierarchy:

People make decisions based on what they remember! (not some objective evaluation of truth) So what will they remember of your presentation?

  • People remember what they hear first and what they see last.
  • People cannot avoid compariing things to one another, vs a fixed standard.
  • To be persuaded, we listen, compare, reconcile, ...
Next: QCon 2009: Continuous Deployment
Previous: QCon 2009: Adventures of an Agile Architect