Dr. U. Assmann, Software Engineering 1 Dr. U. Assmann, Software Engineering 2

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Dr. U. Assmann, Software

Engineering 1

Configuration Management

Dr. U. Aßmann

Research Center for Integrational Software

Engineering

Dr. U. Assmann, Software Engineering 2

Content

T

Basic Concepts

T

Components

T

Component selection

T

Collaboration

T

Process Support

T

Tools

Basic Concepts

Goal

T

Constructing software from components and frameworks

T

Have several products, but a large reuse

T

Have several versions

T A new version every 2 years

T

Have several variants

T Portability

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Software Configuration

Components

Human

Collaboration

Process

Component Model Protection Build support Process support Version model Variant model Merging

Component Selection

Version Selection Variant Selection Component Selection Workspace Product model Composition languages Repository Remote work Consistency control

History

T

SCCS (Rochkind) 1985

T Files in versions

T Deltas (diffs) between versions T Locking for collaborative work

T

Make (Feldman) 1985

T

RCS (Tichy) 1987

T

Shape (Mahler) 1992

T

Feature Logic (Zeller, Snelting) 1995

The Version/Variant Universe

Versions Variants

Objects/Components

Alternative View

Historical

(Versions) Logical (Variants)

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The Variant Parameter Universe

T

A n-dimensional space (with n parameters of k variants)

Parameter A

Parameter B

Parameter C

The Variant Parameter Universe

T

A n-dimensional space (with n parameters of k variants)

OS Processor Window system NT Win Linux Mac XSunNews i486 Alpha PowerPC

The Version Universe

T

A branching tree of unknown depth

T

Every new modification either generates a new child

T

Or a branch

_0.2 0.3 1.0 0.2.1.1 0.3.1.1 0.3.1.2 1.1 Dr. U. Assmann, Software

Components in Repositories and

Workspaces

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Components

T Component model

T Files (main case, unfortunately) T Objects T Documents T Often untyped! T Version model T Branching T Variant model T N-dimensional space

T Often realized by conditional compilation with #ifdef’s T Baseline

T Identify a product as a set of components with specific version and variant configuration

Repository and Workspace

T

To allow programmer modifications, SCM tools always

maintain a repository and programmer-specific

workspaces

T

Repository realization:

T File (SCCS, RCS) T Set of files

T Tree of files (cvs, subversion) T Object base (Damokles) T Data base (ClearCase) T Graph of files

T Special repository on file system level (odin, prcs)

Files As Components (SCCS, RCS)

T The earliest configuaration management tools provided versioning

on files.

T There is a working version and a repository version of the file T A change that is commited from the working version to the

repository file is called a delta

T Users may “undo” changes/deltas and retrieve old versions with version identifiers

T 0.1, 0.2, 0.3, …., 1.0, 1.1, …. 2.0, ….<current>

T If two programmers change concurrently, version numbers branch: T 1.0, 1.1,

T 1.2.1.1, 1.2.1.2, 1.2.1.3, …, 1.2.1.7 T 1.2.2.1, 1.2.2.2

T Two branches may be also merged

RCS commands

T Checkin (ci)

T Create a repository file or update it with a working version T Checkout (co)

T Create a working version from a repository file T Rcsdiff

T Diff two versions T Rcsmerge

T Merge two versions

T RCS stores the newest file as such in the repository file and recalculates older versions by undoing deltas (reverse delta technique)

T SCCS stores the oldest file and recalculates newer versions by applying deltas (forward delta technique) Usually slower!

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RCS symbolic versions

T

RCS can maintain a baseline, I.e., a set of versions of

files that belong together

T And assign the baseline a symbolic name, I.e., “newYork”

T

RCE (extended RCS) can treat trees and has a visual

user interface

View Pathing on Component Trees

(nmake, gmake)

T

Programmers have a view on the test version which has

a view on the official version

... ... ... ... ... ... ... ... ... Official (repository) test Programmer workspace (development)

Simple View Pathing on Trees (cvs)

T

Programmers have a view on the official version

T

All files are physically copied

... ... ... ... ... ...

Development

_repository

Commit (checkin) update (checkout)

Operations in CVS

T

Checkout

T Copy a repository (tree) into a development workspace tree. T Cvs memorizes the repository location, also on the internet T This allows internet collaboration

T All open source projects use CVS

T

Update

T Update the workspace with newer contents of the repository

T

Checkin

T Copy a development workspace into the repository. Merge differences.

T

Diff

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Optimistic Strategy

T

CVS uses optimistic commit, i.e., repositories are not

locked

T

During update operations, it is hoped that the newer

contents of the repository can be merged with the

workspace easily (that’s the optimism)

T

If two programmers changed the same line in a file

differently, a conflict occurs that cannot be merged

automatically

T

The merged file has to be edited by hand to eliminate

the “diffed” lines.

Engineering 22

Component Selection

T ..also called Artefact or Variant Selection

T Component selection selects a set of components with version and variant from a repository.

T The selected items form a partial baseline or a complete baseline. T Selection language:

T Files with piece lists (enumeration of files and version numbers) (cvs, prcs)

T Attributes of components (variants, versions, branches, symbolic names, states “locked” “frozen”, …)

T Pattern matching on attributes

T Logic language to build expressions on patterns

T Set based language (Adele) T Feature logic (Zeller ICE)

T The more powerful the language is the better conflicts and inconsistencies can be avoided!

Adele

T

Estublier, Universite de Grenoble

T

Entity-relationship database

T

Dependency relations

T

Symbolic variant names

T

Set expression based variant selection on attribute

values, constraints, and preferences

T

Query example

Baseline = (window-system=x11

(current status zexperimental))

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Shapetools

T Lampen, Mahler, University of Berlin T On top of the UNIX file system

T Or the object-oriented data base DAMOKLES T Attributed file system, I.e., nicely integrated with OS

T Variants are expressed as attributes

T Name=myfile, type=c, generation=4, revision=3.0, state=saved,

mode=06444, testlevel=low, project=newYork

T Files have states busy, saved, proposed, published, accessed, frozen T Configuration selection by attribute patterns

T , expresses AND ; expresses OR . expresses end-of-rule: doAnAction:

*.c, attr(author,andy), attr(state, busy) ; *.c, attr(mode=755), attrmax(version).

ICE

T

ICE builds on feature logic (A. Zeller)

T

In feature logic terms with attributes

screen1 = [object:screen, resolution:high, speed=high] screen2 = [object:screen, resolution:medium, speed=low]

T

Query example

Baseline = [window-system:x11, {current:C~C, status: ~ experimental}

T

Feature logic unification and resolution can be used for

deduction

T

Easy consistency checking

Collaboration

Collaboration Strategies

T

Pessimistic:

T Programmer has to lock parts or the whole repository T Others may read, but not change

T Too restrictive for groups

T

Optimistic:

T Updates are allowed speculatively T Merge problems must be solved by hand T Almost all tools are now optimistic

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Combination with Regression Tests

T

A regression test feeds a product with a large test suite,

and compares the results with that of the previous

version

T

Regression tests are often poorly supported by SCM

tools

Internet Development

T

Cvs has a browser interface, cvsweb

T

That is the basis of almost all large open source projects

now

T

Large sites offer space for open source projects and use

cvs as the base configuration tool

T www.sourceforge.net

Engineering 31

Process Support

Build Support

T

Main tool: make (Feldman 1975)

T Exists in about 30 variants

T Gmake (gnu) is one of the powerful ones T Cook, odin, are other nice ones

T

Rule based

T If component A is newer than its dependent component B T Then redo B’s production

T

Lazy system builds

T Systems are rebuilt (recompiled, relinked, reconfigured) only if something has changed

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Make as Wavefront

T It builds a graph of

dependencies between components from the rules

T Annotates the actions from the rule to the edges T That must be acyclic T Make detects which nodes in

the graph have changed, I.e., are newer as their successors T And then executes a wavefront

on the dag

T Executing the production actions annotated to an edge

Base components

Product changed

Auto Configuration

T

Gnu autoconf is a makefile generator

T Generates a configure script

T configure generates at installation time makefiles for different machines, operating systems, environments automatically

T

Based on macro processing and a macro library

T

Other tools

T Amake T Perl tools Dr. U. Assmann, Software

Other Tools

PRCS

T

Hilfinger, Berkeley

T

Is a nice improvement of cvs

T

Usually faster since after a commit it does not update

workspace files (which cvs does)

T

Maintains information about the product centrally in a

project file *.prj

T

Simpler management of the projects

T

Internet version is being worked on

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Rational ClearCase

T

One of the market leaders in commercial SCM

T

Good quality control over complete projects

T

Stores attributes with files

T

Files are stored in a database

T

Support of subsystems (packages): identifiers, releases

T

Activity table for merge of subsystems

T

Smart recompilation of parts

Subversion

T

Newest hit of the internet open source projects

T

http://subversion.tigris.net

T

Allows everything based on html browsers

T

Fully internet based

T

Automatic conversion from cvs

Literature

T J. Estublier. Software Configuration Management: A Roadmap. Future of Software Engineering, Limerick, Ireland. ACM 2000. T A. Midha. Software Configuration Management for the 21stCentury.

Bell Labs Technical Journal 1997.

T S. Dart. Concepts in Configuration Management Systems. CMU. T A. Zeller. Unified Versioning through Feature Logic. ACM

transactions on Software Engineering and Methodology. Vol 6, No 4, 1997.

T A. Mahler, A. Lampen. An Integrated Toolset for Engineering Software Configurations. IEEE Sup. On Practical Software Development Environments. SE Notes 13, No 5. T R. Conradi, B. Westfechtel. Version Models for Software

Configuration Management. ACM Transactions on Programmming Languages and Systems.