Understanding and Propagating Architectural Changes

How can we manage changes in product line architectures?

Christopher Van der Westhuizen and Andre van der Hoek

Presented by Jaime Acosta

Problems

• Capturing architectural changes– ADLs with version support– ASCII diff– XML diff

• Understanding differences introduced– Propagating changes in similar systems

Example – Target Display – system changes

Target Display

MapDisplay

DistanceCalc

GPS Data

Target Display

MapDisplay

GPS Data

Logger

FileAccess

EntitySelection

FeatureSet

Example – Returning Employee

• Gone for six months• Get up to speed• Understand changes• Number of other products can benefit from

advances• Apply these changes to all in product line

Problems

• Effort• Time• Cost• Expertise

Alleviations

• Automated support– Recognition– Propogation

• Where has this problem been tackled before?

Solution

• Configuration Management– Understanding nature of src code changes– Propagate changes to other versions of systems

• Requires– Differencing – Merge

Example – an issues in product line architectures

Target Display for customer A

MapDisplay

ARDS Data

EntityControl

FeatureSet

Target Display for customer B

MapDisplay

GPS Data

Logger

FileAccess

EntitySelection

FeatureSet

Target Display for customer C

MapDisplay

DistanceCalc

GPS Data

CM Approaches

• Plain text-based– Line by line differencing/merging

• Does not capture architectural semantics

• XML based– Element based differencing/merging

• Still does not provide desired level of functionality

• Replacement is not supported

Contributions

• Representation for product line architectures– xADL schema

• Algorithm for Difference– Based on xADL schema

• Algorithm for Merge– Based on xADL schema

xADL 2.0

• Every ADL shares common modeling concepts• Allows for extension• Example extensions to structures and types

schema– Options – optional entities– Variants – variable types– Versioning – different versions of entities

Contribution 1: Representation of Product Line Architectures

• xADL– Authors extension to allows documenting changes

Contribution 1: XML Schema

• All required data is in the diff– Do not need original architecture– More efficient for merging with new architecture

• Allows universal algorithms– Tool support– Extension of components

Contribution 1: XML Schema

• Every element has a uniqueID– Differencing– Merging– This holds even in different arch specifications

• No direct support for replacements– Simplicity– Separate treatment of difficult problem

• Must describe– Adds– Removes– Replacements

Contribution 2: Differencing Algorithm

Contribution 2: Differencing Algorithm – Adds/Removes• Input:

– Product line architecture 1– Product line architecture 2

• Output:– XML representing architectural differences

• Additions and Removals

Contribution 2: Differencing Algorithm – Adds/Removes

• Example

Contribution 2: Differencing Algorithm – Adds/Removes

Contribution 2: Differencing Algorithm - Replacements• List of adds and remove is not sufficient

• Knowing about substitution is important– Changes in large systems are easier to understand

• Higher level concept

Contribution 2: Differencing Algorithm - Replacements• Input:

– Additions– Removals

• Output:– Replacement sets

• Idea– Upon replacement, must be old link and new link– Use these as starting points and form groups

Contribution 2: Differencing Algorithm - Replacements

• Example

Contribution 2: Differencing Algorithm - Replacements

• We now have a comprehensive diff– We can see the changes in an architecture– We can compare two architectures– How to apply advances to other architectures?

Contribution 3: Propagation

• Input:– Diff– Target architecture

• Output:– Target architecture with enhancements

Contribution 3: Propagation

Contribution 3: Propagation

Limitations

• Only works for product line architectures• Must be very similar• Must have the same core• Dangerous if code is manually changed• What if you don’t want all of the changes?• Is there any support at the source code level?

Future Work

• Graphical Interface

• Differencing and merging for dynamic updates

• Runtime optimizations

Examples of xADL

Examples of xADL (component)<types:archTypes xsi:type="types:ArchTypes"/> <types:archStructure types:id="archStructureffa80164-77374a95-89b923a6-2fd90003" xsi:type="types:ArchStructure"> <types:description xsi:type="instance:Description">TargetSystem1</types:description> <types:component types:id="componentffa80164-773816af-c279a053-2fd90008" xsi:type="types:Component"> <types:description xsi:type="instance:Description">GPSData</types:description> <types:interface types:id="interfaceffa80164-773a1cc0-0552091f-2fd901a0" xsi:type="types:Interface"> <types:description xsi:type="instance:Description">gpsIfx</types:description> <types:direction xsi:type="instance:Direction">none</types:direction> </types:interface> </types:component>

Examples xADL (connector)

<types:connector types:id="connectorffa80164-773944fd-94c9a164-2fd900d9" xsi:type="types:Connector"> <types:description xsi:type="instance:Description">connector1</types:description> <types:interface types:id="interfaceffa80164-773a3ea0-35d24a71-2fd901c7" xsi:type="types:Interface"> <types:description xsi:type="instance:Description">connector1Ifx1</types:description> <types:direction xsi:type="instance:Direction">none</types:direction> </types:interface> <types:interface types:id="interfaceffa80164-773a7501-990a20d2-2fd901ef" xsi:type="types:Interface"> <types:description xsi:type="instance:Description">connector1Ifx2</types:description> <types:direction xsi:type="instance:Direction">none</types:direction> </types:interface> </types:connector>

Examples of xADL (link)

<types:link types:id="linkffa80164-7739f487-28162479-2fd9017a" xsi:type="types:Link"> <types:description xsi:type="instance:Description">gpsConnLink</types:description> <types:point xsi:type="instance:Point"> <instance:anchorOnInterface xlink:href="#interfaceffa80164-773a1cc0-0552091f-2fd901a0" xsi:type="instance:XMLLink" xlink:type="simple"/> </types:point> <types:point xsi:type="instance:Point"> <instance:anchorOnInterface xlink:href="#interfaceffa80164-773a3ea0-35d24a71-2fd901c7" xsi:type="instance:XMLLink" xlink:type="simple"/> </types:point> </types:link>

Exercise• What would the diff look like assuming no replacements? • Don’t worry about xml syntax, just list entities in plain text. (e.g. removeList: ARDSData… addList: GPSData,…)

Target Display for customer A

MapDisplay

ARDS Data

EntityControl

FeatureSet

Target Display for customer B

MapDisplay

GPS Data

Logger

FileAccess

EntitySelection

FeatureSet

Thank you

Exercise• What would the replacement sets be for the following?

Target Display for customer B

MapDisplay

GPS Data

Logger

FileAccess

EntitySelection

FeatureSet

Target Display for customer C

MapDisplay

DistanceCalc

GPS Data