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James HerbslebCarnegie Mellon University

jdh@cs.cmu.eduhttp://conway.isri.cmu.edu/~jdh/

The Architecture of Coordination

The author gratefully acknowledge support by the National Science Foundation under Grants IIS-11 0414698, IIS-0534656, and IGERT 9972762

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Architectures and Organizations

Level of an industry− E.g., modular clusters

Level of an organization− E.g., matching hypothesis

Level of a practicing architect, manager, or engineer− Architectural decisions define coordination

problems− Understanding and managing impact of decisions

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Today . . .

How can you measure the match of an organization with the structure of the software it is producing?

Coordination theory about the “modularity mismatches” – the failures or limits of modularity

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Product Structure: Conway’s Law

• “Any organization that designs a system will inevitably produce a design whose structure is a copy of the organization's communication structure.”

M.E. Conway, “How Do Committees Invent?” Datamation, Vol.14, No. 4, Apr. 1968, pp. 28–31.

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Conway’s LawComponents

Software

Teams

Organization

Homomorphism

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Designing Coordination ProblemsComponents

Software

Teams

Organization

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Designing Coordination ProblemsComponents

Software

Teams

Organization

?

What kind of coordination is required?

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Measuring Coordination Requirements (CR)

X X =

TaskAssignments

Task Dependencies

(A) (D) (AT)

CoordinationRequirements

(CR)

a11 … a1k

an1 … ank

d11 … d1k

dk1 … dkk

a11 … a1n

ak1 … akn

cr11 … cr1n

crn1 … crnn

Socio-Technical Congruence and Productivity

Concept

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Coordination in a Distributed Project

• Software firm, 1 product, 114 developers• 8 teams, 3 locations, all in US• Product separated into components• Each component assigned to 1 team

Cataldo, M., Wagstrom, P., Herbsleb, J.D., Carley, K. (2006). Identification of coordination requirements: Implications for the design of collaboration and awareness tools. In Proceedings, ACM Conference on Computer-Supported Cooperative Work, Banff Canada, pp. 353-362.

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A Word About Tools and Data• Use archival data from large software

development project• Modification request (MR) system

– Users, testers, developers request changes– Bug fixes, new functionality

• Version control system– Maintains all changes to all files– Some set of changes correspond to each MR– Has data about who made change when

• Communication data– IRC chat– Discussions within MR system

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Measuring Coordination Requirements (CR)

X X =

TaskAssignments

Task Dependencies

(A) (D) (AT)

CoordinationRequirements

(CR)

a11 … a1k

an1 … ank

d11 … d1k

dk1 … dkk

a11 … a1n

ak1 … akn

cr11 … cr1n

crn1 … crnn

Socio-Technical Congruence and Productivity

Files changedtogether

Developermodified files

Transpose ofdeveloper

modified files

Who needs tocoordinate with

whom

Concept

Data

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Volatility in Coordination Requirements

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Week

Per

cent

age

Change in Coordination Req. Out-Group Coordordination Req.Change in coordination group Members of other teams

Pro

port

ion

Week

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Measuring Congruence

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Socio-Technical Congruence and Productivity

Diff (CR, CA) = card { diffij | crij > 0 & caij > 0 }

Congruence (CR, CA) = Diff (CR, CA) / |CR|

CoordinationRequirements

(CR)

ActualCoordination

(CA)

cr11 … cr1n

crn1 … crnn

ca11 … ca1n

can1 … cann

• Team structure• Geographic location• Use of chat• On-line discussion

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Predicting Resolution TimeTable 2: Results from OLS Regression of Effects on Task Performance (+ p < 0.10, * p < 0.05, ** p < 0.01).

 

Model I Model II Model III Model IV(Intercept) 2.987** 3.631** 1.572* 1.751*

Dependency 0.897* 0.653* 0.784* 0.712*

Priority -0.741* -0.681* -0.702* -0.712*

Re-assignment 0.423* 0.487* 0.304* 0.324*

Customer MR -0.730 -0.821 -0.932 -0.903

Release -0.154* -0.137* -0.109* -0.098*

Change Size (log) 1.542* 1.591* 1.428* 1.692*

Team Load 0.307* 0.317* 0.356* 0.374*

Programming Experience -0.062* -0.162* -0.117* -0.103*

Tenure -0.269* -0.265* -0.239* -0.248*

Component Experience (log) -0.143* -0.143* -0.195* -0.213*

Structural Congruence -0.526* -0.483*

Geographical Congruence -0.317* -0.312*

MR Congruence -0.189* -0.129*

IRC Congruence -0.196* --

Interaction: ReleaseX Structural Congruence 0.007 0.009

Interaction:ReleaseXGeographical Congruence -0.013 -0.017

Interaction: Release X MR Congruence -0.009+ -0.011+

Interaction: Release X IRC Congruence -0.017* --

N 809 809 1983 1983

Adjusted R2 0.787 0.872 0.756 0.854

(* p < 0.05, ** p < 0.01)

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Average Level of Congruence for Top 18 Contributors

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Release 1 Release 2 Release 3 Release 4

Con

grue

nce

(avg

.)

IRC MR Structure Geography

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Average Level of Congruence for the Other 94 Developers

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Release 1 Release 2 Release 3 Release 4

Con

grue

nce

(avg

.)

IRC MR Structure Geography

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The Story So Far . . .• Coordination requirements are highly volatile.• Congruent coordination activities are associated with

performing the work faster.• The top developers behave much more congruently

than the rest.

• Have replicated congruence finding on GNOME projects• Have experimented with many different ways of

computing dependencies– Logical dependencies the most predictive by far

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Theory• Build on modularity/architecture literature

– Product structure and task structure• Build on network analysis

– Network attributes matter – Relations among people, decisions,

components• Methodology: build on idea of logical

dependencies

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Coordination: Five Propositions

• P1: Design progresses by making decisions.• P2: Decisions are linked by constraints in a potentially large and

complex network. – The “decision network”

• P3: The need for coordination among individuals arises from– Properties of the decision network– Assignment of decisions to people

• P4: Effective coordination is the result of coordination actions, moderated by coordination capacity.

• P5: Coordination breakdowns occur when effective coordination is insufficient for coordination needs

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Example Domain: Field Robotics

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Example Network: Field Robotics

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Coding Method• Meeting segments

Avionics Optics Software

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Coding Method• Meeting segments• Divide into decision discussions

Avionics Optics Software

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Coding Method• Meeting segments• Divide into decision discussions• Code according to components involved

in the decision discussion– Co-occurrence much like logical dependency

Avionics Optics Software

Camera Mobility

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Example Network: Field Robotics

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Hardware Discussions

Newman Modularity: .39

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Software Discussions

Newman Modularity: .03

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Network Theory of Coordination

CoordinationEffectiveness

CoordinationEffectiveness OutcomesOutcomes

CoordinationRequirements

CoordinationRequirements

CoordinationActions

CoordinationActions

CoordinationCapacity

CoordinationCapacity

Task Assignment

Task Assignment

DecisionNetwork

DecisionNetwork

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Challenges• Planning

– Predicting coordination requirements– Assessing coordination capacity– Choosing optimal coordination actions

• Coordinating– Monitoring for unexpected mismatches– Organizational tactics, architectural tactics

• Theorizing– Principles, patterns for network dependencies– Prior theories as special cases