introduction to software engineering lecture 6
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Introduction to Software Engineering Lecture 6. André van der Hoek. Today’s Lecture. Architecture design. Magic View. Requirements. Code. Professional View. Requirements. Code. Implementation phase. Testing phase. Test. Verify. ICS 52 Life Cycle. Requirements phase. Verify. - PowerPoint PPT PresentationTRANSCRIPT
Introduction to Software Engineering
Lecture 6
André van der Hoek
Today’s Lecture Architecture design
Magic View
Requirements
Code
Professional View
Requirements
Code
ICS 52 Life CycleRequirements
phaseVerify
DesignphaseVerify
ImplementationphaseTest
TestingphaseVerify
Design Architectural design
High-level partitioning of a software system into separate modules (components)
Focus on the interactions among parts (connections)
Focus on structural properties (architecture) “How does it all fit together?”
Module design Detailed design of a component Focus on the internals of a component Focus on computational properties
“How does it work?”
Spotify Example
Architecturaldesign
Moduledesign
Provided InterfaceAudio Encoder
Required Interface
Provided InterfaceSelector
Required Interface
Provided InterfaceAudio PlayerRequired Interface
Com
pres
sor
Provided Interface
Enco
der
Read
er
Required Interface
Design Interaction
Architectural design(this lecture)
Module design(next lecture)
Architectural DesignElements
Floors Walls Rooms
Types Office building Villa Aircraft hanger
Styles Colonial Victorian Southwestern
Rules and regulations Electrical Structural
Elements Components Interfaces Connections
Types Office automation Game Space shuttle control
Styles Pipe and filter Layered Implicit invocation
Rules and regulations Use of interfaces Methods of change
Build
ings
Software
Software Architecture: Essentials Components
What are the main parts? What aspects of the requirements do they
correspond to? Where did they come from? Examples: filters, databases, GUIs, interpreters
Connections How do components communicate? Examples: procedure calls, messages, pipes, event
broadcast Topology
How are the components and connections organized topologically?
Constraints (including constraints on change)
Comparison to Module Design
Architecture Modules• interactions among parts •
implementations of parts• structural properties • computational
properties• system-level performance • algorithmic
performance• outside module boundary • inside module
boundary
Where do Architectures and Components Come From? Architectures: typically driven by kind of
application Often possible to solve one problem many
different ways Components: many design strategies
ICS 52 component strategy: Component design by information hiding Designing systems for ease of extension and
contraction An OO design approach
Rationale: design systems that have a long, useful lifetime
We Can Do Anything…
Provided InterfaceBig Component
Required Interface
Provided InterfaceTiny Component
Required InterfaceProvided Interface
B ComponentRequired Interface
Provided InterfaceMr. Component
Required Interface
Provided InterfaceA Component
Required Interface
Provided InterfaceYet Component
Required Interface
Provided InterfaceSome Component
Required Interface
Provided InterfaceOne Component
Required Interface
Provided InterfaceMrs. Component
Required Interface
…But Style Has Proven to Help Architectural styles restrict the way in
which components can be connected Prescribe patterns of interaction Promote fundamental principles
Rigor, separation of concerns, anticipation of change, generality, incrementality
Low coupling High cohesion
Architectural styles are based on success stories Almost all compilers are build as “pipe-and-
filter” Almost all network protocols are build as
“layers”
Style 1: Hierarchy
Connections are function or method calls
Provided InterfaceMain component
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Provided InterfaceSubcomponent
Required Interface
Style 2: Client-Server
Connections are remote procedure calls or remote method invocations
Provided InterfaceClient
Required Interface
Provided InterfaceClient
Required Interface
Provided InterfaceClient
Required Interface
Provided InterfaceServer
Required Interface
Style 3: Blackboard
Provided InterfaceBlackboard
Connections are encapsulated global variables
Provided InterfaceOne “Part”
Required Interface
Provided InterfaceMy “Bit”
Required Interface
Provided Interface Her “Piece”Required Interface
Provided InterfaceA “Part”
Required Interface
Provided Interface Another “Piece”
Required Interface
Provided InterfaceHis “Bit”
Required Interface
Style 4: Peer-to-Peer
Connections are remote procedure calls or remote method invocations
Provided InterfacePeer
Required Interface
Provided InterfacePeer
Required Interface
Provided InterfacePeer
Required Interface
Style 5: Pipe-and-Filter
Connections are pipes (also called data flows)
Prov
ided
Inte
rface
Filte
rRe
quire
d In
terfa
ce
Prov
ided
Inte
rface
Filte
rRe
quire
d In
terfa
ce
Prov
ided
Inte
rface
Filte
rRe
quire
d In
terfa
ce
Prov
ided
Inte
rface
Filte
rRe
quire
d In
terfa
ce
Style 6: Implicit Invocation
Connections are events on the software bus
Provided InterfaceComponentRequired Interface
Provided InterfaceComponentRequired Interface
Provided InterfaceComponentRequired Interface
Provided InterfaceComponentRequired Interface
Provided InterfaceBus
Required Interface
Style 7: Layers (Take 1)
Connections are function or method calls + “something in between”
Provided InterfaceLayer 4
Required Interface
Provided InterfaceLayer 3
Required Interface
Provided InterfaceLayer 2
Required Interface
Provided InterfaceLayer 1
Required Interface
Provided InterfaceLayer 4
Required Interface
Provided InterfaceLayer 3
Required Interface
Provided InterfaceLayer 2
Required Interface
Provided InterfaceLayer 1
Required Interface
Style 7: Layers (Take 2)
Connections are function or method calls
extended
basic
corecore
Many Other (Variants of) Styles Interpreters Batch sequential Data abstraction/OO systems Model View Controller (MVC) …
Different Styles, Different Situations Layers
Seven network layers in OSI reference model
Blackboard Databases Inventory/stock management systems
Client-server Web browser/Web server
Peer-to-peer Distributed databases Communication satellites
Choosing the Right Style Ask questions on whether a certain style
makes sense The Internet as a blackboard
Does that scale? Stock exchange as a layers
How to deal with the continuous change? Math as hierarchy
How to properly call different modules for different functions?
Draw a picture of the major entities Look for the natural paradigm Look for what “feels right”
Mixing Styles Is Often Necessary
Blackboard + Client-Server
Provided InterfaceBlackboard
Provided InterfaceOne “Part”
Required Interface
Provided InterfaceMy “Bit”
Required Interface
Provided Interface Her “Piece”Required Interface
Provided InterfaceA “Part”
Required Interface
Provided Interface Another “Piece”
Required Interface
Provided InterfaceHis “Bit”
Required Interface
Provided InterfaceBlackboard
Provided InterfaceOne “Part”
Required Interface
Provided InterfaceMy “Bit”
Required Interface
Provided Interface Her “Piece”Required Interface
Provided InterfaceA “Part”
Required Interface
Provided Interface Another “Piece”
Required Interface
Provided InterfaceHis “Bit”
Required Interface
Original Blackboard
Mixing Styles is often Necessary
Blackboard + Implicit Invocation
Provided InterfaceBlackboard
Provided InterfaceOne “Part”
Required Interface
Provided InterfaceA “Piece”
Required Interface
Provided InterfaceSome “Bit”Required Interface
Provided InterfaceBus
Required Interface
Mixing Styles Is Often Necessary
Pipe-and-Filter + Client-Server + Hierarchy
Pipe FCallsProvided Interface
Audio EncoderRequired Interface
Provided InterfaceTuner
Required Interface
Provided InterfaceAudio PlayerRequired Interface
Your Tasks1. Read and study slides of this lecture
2. Memorize the architectural styles
3. Read and study Chapter 11 of van Vliet