SCM a la Carte

C-SPIN03/01/2006Ross Fraser

AGENDA

IEEE/DoD Standard Definition of SCM Introduction to Pattern Languages SCM Pattern Language

IEEE/DoD StandardDefinition

The purpose of Software Configuration Management is to establish and maintain the integrity of the products of the software project throughout the project’s software life cycle.

(Configuration Management Principles and Practice, Anne Mette Jonassen Hass)

IEEE/DoD StandardActivities

Configuration Identification Configuration Change Control Configuration Status Accounting Configuration Audits

A New Definition

SCM is a formal process which serves to prevent or mitigate anticipated failures of communication, coordination or control (C3).

SCM is appropriate when impediments to the success of informal methods are present.

Background to pattern languages

1975-1979: Christopher Alexander 1987: Cunningham and Beck 1994: First Pattern Languages of

Program Design (PLoP) conference 1995: “Gang of Four” 1999: Brown, McCormick and

Thomas 2003: Berczuk and Appleton

What is a pattern?

A pattern is a solution to a problem in a context.

A pattern is a named nugget of instructive information that captures the essential structure and insight of a successful family of proven solutions to a recurring problem that arises within a certain context and system of forces.

What is a pattern language?

A pattern language is a group of patterns in relation to each other.

A pattern language can contain patterns at different levels of applicability

What are the advantages? A pattern is named. A pattern addresses a problem. A pattern works within a context. A pattern is reusable. Patterns fit together into a pattern

language. A pattern can be large or small in scope. A pattern language is extendable.

SCM Pattern LanguageStructure

Domains Procedures Components

SCM Pattern LanguageDomains

Delivery

Inventory

Agreements

Customers

Developers

Users

Examples of “Agreements” Problems

Uncontrolled increase in scope (“feature creep”)

Uncommunicated changes to requirements

Unidentified requirements Unimplemented requirements

Examples of “Inventory” Problems

Lost source code modules Unauthorized code changes Changes that “break” existing

code Loss of valid code changes Proliferation of unidentified files

Examples of “Delivery” Problems

Delivery of obsolete software modules

Delivery of incompatible modules Delivery of inadequately tested

software Delivery of unexpected changes

Inventory Procedure #1

DEVSourc

e

QASourc

e

PRODSourc

e

DEVLoad

QALoad

PRODLoad

Inventory Procedure #2

CommonSource

DEVLoad

QALoad

PRODLoad

Private Workspace

Inventory Component: Gatekeeper Use events to trigger automated

QC/SCM actions Automated build Require comments and other meta-data Require link to change request or defect Syntax checking Standards checking Automated smoke test

Can be a component of either procedure

Resources in Print Fletcher Buckley: Implementing

Configuration Management: Hardware, Software, and Firmware

Wayne Babich: Software Configuration Management: Coordination for Team Productivity

Steve Berczuk & Brad Appleton: Software Configuration Management Patterns: Effective Teamwork, Practical Integration

Resources on the Web

http://www.cmcrossroads.com/bradapp/docs/patterns-intro.html (patterns)

http://www.cmcrossroads.com/bradapp/acme/index.html (SCM)

http://www.scmpatterns.com/

Q&A Discussion

The presentation was followed by a ‘workshop’ in which the audience discussed various problems and solutions amongst themselves while the presenter took notes. Here are some of the discussion items.

Q&A DiscussionWho "owns" the SCM process? Various answers were supplied by members of the

audience: a separate SCM group (although they tend to be pre-

occupied with issues of getting the SCM technology to work, and thus neglectful of the underlying process)

operations (after all, they are most immediately impacted by an unsuccessful delivery)

change control board Since we have argued that SCM tries to resolve

communication problems between people, then for each part of the process, the people who are involved in that particular communication step should be allowed to negotiate a process that works for both (or all) of them.

Q&A Discussion

How do you use SCM to manage data?No one had a good answer to this, but we

observed that this can apply to various kinds of data, including control data and test data. It was also noted that a process for controlling data should not only deliver the correct data, it should also protect sensitive data, such as test data copied from production, with social security numbers in it.

Q&A DiscussionOne participant had a suggestion for protecting

against the delivery of incompatible or obsolete code modules. (This especially applies to the inventory process #1, which is vulnerable to losing concurrency between source and object code.) The list of items to promote should not only include names and version numbers, but also size and a generated checksum for each load module that will be constructed from those items. These can be used to verify (with a reasonable degree of certainty) that the production load modules match the load modules which were tested.