Watts Humphrey IBM director of programming and vice

Watts Humphrey • IBM director of programming and vice -president of technical development • Joined CMU Software Engineering Institute in 1986 • Initiator and lead developer of CMM, PSP, TSP • Recipient of national medal of technology • “Father of software quality”

Process • What to do at each step – Waterfall – Unified Process – Agile (XP, Scrum) • How to do it – Capability Maturity Model (CMM) – Personal Software Process (PSP) – Team Software Process (TSP)

Measurement-based Measure the learning process, not of self improvement the product in developing software customized for personal conditions el v le r e e in g n e l a u id iv d in – PSP TSP – team level l CMM – management leve

CMM • Originally assessment procedure to allow Do. D to screen contractors • 1980 s— 1990 s: Developed into a general framework for quality certification – Define 5 maturity levels • 2000 s: evolved into CMMI – General management processes in development, services, and acquisitions – Add people-CMM, later also DMM (data management maturity) – Not only for software but all areas of industry

1. Initial: code and test w/o planning; ad-hoc …Add management control and defined SE processes… 2. Managed: plan with stakeholders, provide resources, monitor execution milestones; no compromising during crisis …Add standards and apply across organization… 3. Defined: common processes tailored for each project’s needs; rigorous definition of processes …Add process measurement and analysis… 4. Quantitatively Managed: based on quantitative process/quality objectives; predictions …Add continuous adjustments across organization… 5. Optimizing: proactively fix performance gaps

Nuances • Measurement is not used for ranking – Goal is good data about project/process – Using it for ranking will lead to bad data • Discipline, not regimentation – Prescribe procedures for how things are done – Reduce friction and waste – Don’t dictate what to do, don’t reduce creativity – Creativity ≠ anarchy

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PSP • Personal perspective of improvement a-la CMM – Can be done by individuals – Not dependent on CMM environment • Make the routine work more predictable and efficient • Customizable per individual • Customizable with time as an individual’s capabilities improve Watts S. Humphrey / A Discipline for Software Engineering, Addison-Wesley 1995

PSP 0 • Use whatever work habits you have • Collect data about how you perform “If you don’t know what you are doing, it is hard to improve it” • Use detailed predefined forms – Filling form is easier than starting from scratch – Annoying but worth it on the long run – Form structure may be customized later

Time recording log Side effect: discover how much you are interrupted and the benefits of reducing interruptions

Defect recording log

Project plan summary

PSP 1 • • Develop personal planning process Size estimation Test report Understand Required basis: relationship between – Coding standard – Precise size measurements size and required time • Outcomes: – Task planning – Schedule planning Make commitments you can meet

Project loop Multi-project self improve - ment loop

Size • The basic metric is KLo. C • But with important consistency constraints – One developer – Same language (or separate counts per language) – Same purpose (or separate counts for project, test, etc. ) • Well-defined standard of how to count – Braces, empty lines, comments…

PROxy-Based Estimation (PROBE) • Identify objects based on conceptual design • Find proxies for objects in historical database • Estimate total object Lo. C based on these proxies – Use log-normal object size categories • Use linear regression to estimate total program Lo. C and range based on objects Lo. C

Improvement • Estimates always fluctuate and have errors – Natural variability and lack of information – Builtin bias • By independently estimating small components and summing, variability is reduced ØBetter precision • This makes it easier to identify and correct bias ØBetter accuracy

Schedule • Use regression of historical data on estimated size and actual time – This is productivity = Lo. C / hour – Regression allows for better prediction than average, plus expected range • Distinguish productivity on new code, modified code, and reused code • Track actual productivity and adjust prediction – Alert management of change

PSP 2 • Develop personal quality management process • Code reviews • Design reviews • Including personal reviews • More effective than testing – When faced with a bug, need to find logical cause – In reviews you start with the logic

PSP 3 • Previous stages used small programs for learning – Linear waterfall-like phases • Not suitable for large programs • Final stage is to develop a personal cyclic development process • Basic idea: partition into iterations that can be handled using PSP 2

TSP • • • PSP is a personal process Maximal project size is limited Need a team process to build larger projects TSP designed for engineers with PSP training Basically an iterative process – Cycle of 3 -4 months – Structured launch (re-launch) to plan the cycle – Tracking and monitoring to ensure plan is followed

Summary • PSP is hard work – Tedious monitoring and filling forms – Requires significant self-discipline – Takes long time to show returns on investment • Provides professional confidence • “Takes the creative fun out of software development”? ? ? Ø Humphrey: on the contrary! Makes the routine part efficient leaving more time for creative fun