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Framework is ..Framework is ..
Framework isFramework is……
Douglas C. Schmidt Says..Douglas C. Schmidt Says..FrameworksFrameworks define define “semi“semi--complete” applicationcomplete” applicationthat embody domainthat embody domain--specific object structures and functionality.specific object structures and functionality.
Class Library Class Library Component Component ArchitectureArchitecture
App SpecificApp SpecificLogicLogic
OO DesignOO Design
EventEventLoopLoop
DATABASEDATABASE ADTsADTs
MATHMATH NETWORKINGNETWORKING
GRAPHICSGRAPHICS GUIGUI
SingletonSingleton StrategyStrategy
ReactorReactor AdapterAdapter
StateState Active ObjectActive Object
InvocationsInvocations
SelectionsSelections
Application BlockApplication Block
Design PatternDesign Pattern
Libraries is..Libraries is..
DATABASEDATABASE
SingletonSingleton
GRAPHICSGRAPHICS
AdapterAdapter
EventEventLoopLoop
ReactorReactor
NETWORKINGNETWORKING
Active ObjectActive Object
GUIGUI
StateState
App SpecificApp SpecificLogicLogic
MATHMATH
ADTsADTs
CallbacksCallbacks
InvocationsInvocations
Application Application FrameworkFrameworkComponent ArchitectureComponent Architecture
But Framework is ..But Framework is ..
Why Do You Need Framework?Why Do You Need Framework?
Avoid Duplication Productivity
Welcome toWelcome to
My FrameworkMy Framework
Journey!Journey!
“Framework Engineering”, TechED 2007 Europe
“Framework Design Guidelines” , Addison Wesley
Krzysztof Cwalina
Program Manager on .NET Framework Team
5 Topics..5 Topics..
Organization
Planning
Architecture
Design
Development
DO P A V
The most powerful design toolThe most powerful design tool
O
Project Management TriangleProject Management Triangle
Scope
Cost Time
O
Project Management Triangle Project Management Triangle
Organization
O
DODO understand how understand how organizational structure, organizational structure, culture, and decision making processesculture, and decision making processes impaimpact your product. ct your product.
O
Conway's lawConway's law
If you have 4 groups working on a compiler,
you’ll get a 4-pass compiler.
O
Organization Structure
Software Structure
O
Conway's Clean State ApproachConway's Clean State Approach
1• Define the business mission• Define the business mission
2• Learn the business process from business owners• Learn the business process from business owners
3• Re-engineer these process to fit the mission• Re-engineer these process to fit the mission
4
• Structure the IT organization to support the reengineered business processes.
• Structure the IT organization to support the reengineered business processes.
O
Your Company Culture Is ..Your Company Culture Is ..
Voluntary ??O
Familial ??O
Your Company Culture Is ..Your Company Culture Is ..
Peremptory O
Organizational InfluencesOrganizational InfluencesSize of OrganizationSize of Organization
Small Team
Simple Design
Consistency Design
Focus on 80/20 Rules
O
Large Team
Organizational InfluencesOrganizational InfluencesSize of OrganizationSize of Organization
Powerful Design
Lack Consistency
Remove Requirements
O
Organizational InfluencesOrganizational InfluencesOrganization’s Culture/BiasesOrganization’s Culture/Biases
Customer-Focused
End-2-End Scenarios
O
Organizational InfluencesOrganizational InfluencesOrganization’s Culture/BiasesOrganization’s Culture/Biases
Technology-Focused
Long Lasting Architecture
O
Decision Making Process is..Decision Making Process is..
O
Ensuring we are building the right thing Ensuring we are building the right thing
P
P
Focus: featuresFocus: features
Results: Results: stability, stability,
incremental incremental
improvements, not improvements, not
great great endend--toto--end end
scenariosscenarios
Peanut ButterPeanut Butter
Focus: scenarios Focus: scenarios
Results: Results: Excitement, Excitement,
breakthroughs, but breakthroughs, but
beware of leaving beware of leaving
existing customers existing customers
behind behind
SkyscrapersSkyscrapers
P
MModeration (oderation (中庸中庸))MileStone = Scenarios + FeatureMileStone = Scenarios + Feature
Planning M1 M2
ReleaseTesting
Feature completeVision statement RTM
Technology Preview Beta 1 Beta 2 RC1
Ensuring the long term health of the frameworkEnsuring the long term health of the framework
A
A
Right Way??Right Way??CChoose right types.hoose right types.
Taxonomy of Taxonomy of TypesTypesLibraries Libraries , Primitives, Abstractions, Primitives, Abstractions
A
PrimitivesPrimitivesVery little policy (behavior design decisions)
Stable design
Commonly appear in publicly accessible APIs
Almost impossible to evolve/change design;
any design changes have huge breaking change impact on other APIs
Example: Int32, String
A
Definition:Libraries are types that are not passed between components
ExamplesEventLog, Debug,
Easy to EvolveLeave old in, add new one
Beware of duplication!
A
LibrariesLibraries
AbstractionsAbstractions
Definition:Abstractions are interfaces or classes with unsealed members that are passed between components.
ExamplesStream, IComponent
Hard to Evolve
Unfortunately, pressure to evolve
A
Primitive Oriented DesignPrimitive Oriented Design
A.K.A. “Handle based design” (functional)
Great evolvability, poor usability (sometimes)
Low level stable primitives + high level reusable components with limited dependencies other than to the primitives
E.g. Type.GetType(object) – works, but not as convenient as Object.GetType
A
for primitive.. for primitive.. C# 3.0 New FeatureC# 3.0 New Featurenamespace MyCompany.StringManipulation {
public static class StringExtensions{
public static bool IsNullOrEmpty(this string s){ return String.IsNullOrEmpty(s);
}
}
}
…
using MyCompany.StringManipulation;
string message= “hello world”;
if(message.IsNullOrEmpty()){
Console.WriteLine(“EMPTY”);
}
Component Oriented DesignComponent Oriented Design
Rich APIs with lots of features, thus with lots of dependencies
Great usability, poor evolvability
Good for higher level components, not for the core of a platform
A
A
DODO Manage Dependencies..Manage Dependencies..
A
Lego, Plug ??
Component is ..
A
.. a set of types that ship and evolve as a unit.
A
Dependency
API
Implementation
Circular
API DependencyAPI Dependency
Component A has an API dependency on component B,
if a type in B shows in the publicly accessible API surface of a type in A.
This includes:Base types and implemented interfaces
Generic parameter constraints
Return types and parameters of members
Applied attributes
Nested types
A
Implemenatin Implemenatin DependencyDependency
If a type in A uses a type in B in its implementation.
Hard Dependencies (required to run)Soft Dependencies (optional)
A
Circular Circular DependencyDependency
Component A depends on component B and
Component B depends on component A (even indirectly).
A
Packaging Packaging PrinciplePrinciple
Package Cohesion PrincipleREP (Release Reuse Equivalency)
CCP (Common Closure Principle)
CRP (Common Reuse Principle)
Package Coupling PrincipleADP (Acyclic Dependencies Principle)
SDP (Stable Dependencies Principle)
SAP (Stable Abstraction Principle)
ARobert C. Martin, Principle of Package Architecture
http://www.objectmentor.com/resources/articles/Principles_and_Patterns.pdf
A
Solution is Layering..Solution is Layering..
A
A
BCLBCL
WPFWPF XMLXML
ReflectionReflection
Circular Circular DependencyDependency
A
GUIGUI
CommCommAnalysisAnalysis
ProtocolProtocolModem Modem
ControlControl
CommComm
ErrorError
DDatabaseatabase
Creating a new packaging.Creating a new packaging.
A
GUIGUI
CommCommAnalysisAnalysis
ProtocolProtocolModem Modem
ControlControl
CommComm
ErrorError
DDatabaseatabase
MessageMessage
ManagerManager
AA
BB
XX
YY
Circular DependencyCircular Dependency
AA
BB
XX
YY<<interface>><<interface>>
BYBY
Adding new interfaceAdding new interface
Heavy DepedencyHeavy Depedency
A
A
Heavy Dependencies and TestabilityHeavy Dependencies and Testability
// your API
public class Tracer {
MessageQueue mq = new MessageQueue(…);
public void Trace(string message){
mq.Send(message);
}
}
// your customer’s program that is hard to test
Tracer tracer = new Tracer();
public void ProcessOrder(Order order){
tracer.Trace(order.Id);
…
}
Inversion of ControlInversion of Control
// your better API
public abstract class TraceListener {
public abstract void Trace(string message);
}
public class Tracer {
TraceListener listener;
public Tracer(TraceListener listener){
this.listener = listener;
}
public void Trace(string message){
listener.Trace(message);
}
}
Dependency InjectionDependency Injection
// your customer’s program that is easier to test
Tracer tracer = new Tracer(new FileListener());
public void ProcessOrder(Order order){
tracer.Trace(order.Id);
…
}
// customer’s program that is even easier to test
Tracer tracer = container.Resolve<Tracer>();
public void ProcessOrder(Order order){
tracer.Trace(order.Id);
…
}
Check out DI Containers (a.k.a. IoC Containers): autofac, Castle Windsor, PicoContainer.NET, Spring.NET, StructureMap, Unity, nInject and others.
http://www.nInject.org
DO balance advances with compatibility.
A
Types of “Compatibility” Types of “Compatibility”
A
CrossCross--VersionVersion
BackwardBackward
ForwardForward
A
CrossCross--RedistRedist..
A
Define what’s a “breaking change”
This definition depends on the objectiveE.g. Enable portable code between Silverlight and .NET Framework
E.g. Enable cross-version portability?
For example, Silverlight interfaces cannot have less members than .NET interfaces, but concrete types can.
A
AVOID duplication and overlap.
A
A
ProblemProblem SpaceSpace Show and TellShow and Tell
PLoP – Capable, Productive and Satisfied Patterns for Productivity
http://hillside.net/plop/plop98/final_submissions/P54.pdf
When the new technology is “10x better”
Make sure you understand the impact on the ecosystem
What would happen if the BCL team added a new String?
What’s the migration path for code using the old API?
A
This is where quality happensThis is where quality happens
D
Is using your framework correctly like…Is using your framework correctly like…
Running across a desert?Running across a desert?
A
DO design APIs by
first writing code samples for the main scenarios
and then
defining the object model to support the code samples.
D
Code SamplesCode Samples
D
Read FileRead File
static void Main(string[] args)
{
StreamReader sr = File.OpenText("MyFile.txt");
string s = sr.ReadLine();
while (s != null)
{
s = sr.ReadLine();
Console.WriteLine(s);
}
}
D
static void Main(string[] args)
{
foreach (string s in File.ReadAllLines("MyFiles.text"))
{
Console.WriteLine(s);
}
}
Feedback (Read File)Feedback (Read File)
D
Object Model ListingObject Model Listing
D
Framework Design Studio Framework Design Studio Assembly ExploerAssembly Exploer
Project -> Add -> Assembly
Download here - http://code.msdn.microsoft.com/fdsD
Framework Design Studio Framework Design Studio Assembly Review CommentAssembly Review Comment
D
Framework Design StudioFramework Design StudioCompare API VersionsCompare API Versions
D
Framework Design StudioFramework Design StudioCompare API VersionsCompare API Versions
Red is removed,
Green is added,
Grey means inherited.
D
Framework Design StudioFramework Design StudioExporting to Microsoft WordExporting to Microsoft Word
Tools -> Export to Document
DO treat simplicity as a feature.
D
Remove Requirements
Reuse Existing Concepts or APIs
Adjust Abstraction Level
Three Example (Evolving Frameworks)
D
DO measure, measure, and measure!
D
Specification Document: QualitiesSpecification Document: Qualities
Performance GoalsBaseline: What do is the best my API could do?
Measure delta from the baseline
Threat ModelsThreat: What is the worst that my component could do?
Mitigate the threats
Same for many other qualities you want your framework to have
D
THE POWER OF SAMENESS
D
When you pick up your rental car….When you pick up your rental car….
Push the seat all the way back
Find an NPR station
Find the exit
Read the manual??Read the manual??
Oh, down to lock…Oh, down to lock…
How to use a key…How to use a key…
Oh, you Oh, you pushpush the PRESS button…the PRESS button…
Who actually Who actually needs needs this data?this data?
You know how to drive your car
All cars work basically the same way
Your rental car is a car
Therefore, you can drive your rental car
That is…
The bits customers get, … or notThe bits customers get, … or not
V
Branches and IntegrationsBranches and Integrations
Main
PU-staging
branch
Feature
branch
Feature
branch
PU-staging
branch
PU-staging
branch
V
AVOID integrating unfinished features.
V
Functional SpecificationDeveloper Design SpecificationTest PlanThreat ModelAPI reviewArchitectural ReviewDependency ManagementStatic AnalysisCode CoverageTesting (Unit and Integration Tests)0 BugsPerformance
V
DO pay your debt.
V
Planning M1 M2
ReleaseTesting
Feature completeVision statement RTM
Technology Preview Beta 1 Beta 2 RC1
Milestone Quality
Milestone Quality (MQ)Milestone Quality (MQ)
Initiatives that are hard to do in regular milestones
Large productivity and efficiency improvements
Infrastructure changes
For example, a new source control system
Refactoring of fragile subsystems
Internal implementation documentation
Bugs backlog
V
DO understand how organizational structure, culture, and decision making processes impact your product.
AVOID peanut-butter in Scenario Based Application.
DO manage your dependencies.
DO balance advances with compatibility.
AVOID duplication and overlap.
DO design APIs by first writing code samples for the main scenarios and then defining the object model to support the code samples.
DO treat simplicity as a feature.
DO measure, measure, and measure!
AVOID integrating unfinished features.
DO pay your debt.
Krzysztof Cwalina, Brad Abrams
Framework Design Guidelines:Conventions, Idioms, and Patterns for Reusable .NET Librarieshttp://channel9.msdn.com/pdc2008/PC58/
http://www.gotdotnet.com/team/fxcop
Douglas C. Schmidt (PLoP Editor, POSA 2, 4 Writter)
JAWS: An Application Framework for High Performance Web Systemhttp://citeseer.ist.psu.edu/81775.html (En)http://www.devpia.com/net2/EvaCast/Lecture/?cu=view&r=11 (Kr)
Ralph Johnson (GoF , Design Patterns)
Evolving Frameworkshttp://st-www.cs.uiuc.edu/users/droberts/evolve.html (En)http://arload.wordpress.com/2008/09/15/evolvingframeworks/ (Kr)
Robert C. MartinPrinciples of Package Architecture (Design Principles and Design Patterns)
http://www.objectmentor.com/resources/articles/Principles_and_Patterns.pdf (En) http://www.devpia.com/net2/EvaCast/Lecture/?cu=view&r=108 (Kr)
For Korean People..
Load to Architecthttp://www.arload.net
EvaCast (Online Free Lecture)http://www.evacast.net
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