‫بسم هللا الرحمن الرحيم‬
‫ والصالة والسالم على رسول هللا‬، ‫الحمد هلل‬
Software Architecture Styles
Hany H. Ammar, Professor,
LANE Department of Computer Science and Electrical Engineering
West Virginia University, Morgantown, West Virginia, USA, and
Visiting Professor, Faculty of Computers and Information, Cairo University, Cairo,
Egypt
Modeling and Documenting
Software Architectures
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OUTLINE
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• SW Systems Mix of Architecture Styles
• Other Important Styles
•
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Software Architectures
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Introduction
Recall the definition of Styles
• An architectural style is a coordinated set of
architectural constraints that restricts the
roles/features of architectural elements
and the allowed relationships among those
elements within any architecture that
conforms to that style.
Introduction
What does it give us?
• An architectural style describes a certain
codification of elements and their
arrangements.
• Conversely, an architectural style
constrains both the elements and their
interrelationships.
• It specifies components and connectors
types
Introduction
Example Component Types
Ex:
Con
nect
or
Type
s
Examples of Popular
Architecture Styles
Families of Architecture Styles
• There is a number of families of styles that has been
defined and used in many software systems Notable
examples are:
1. Independent Components: Event-based
Architectures
2. Virtual Machines
3. Data Flow: Pipes and Filters
4. Data-Centered Systems
5. Call-and Return Architectures
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OUTLINE
•
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
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Architectural Styles
Independent Components
1. Independent Components. Architecture is
viewed a set of independent processes or
objects or components that communicate
through messages.
Two subfamilies:
- Event based systems (implicit and direct
invocation style), and
- Communicating processes family (client-server
style).
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Architectural styles: Event-based Architecture
Some processes post events,
others express an interest in events
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Event-based
Architecture
Event-based Architecture
Implicit Invocation: The Observer
Pattern
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Another Example: Lunar Lander Game
Players Subscribers register to the Game Server that Publishes information
on new Lunar Terrain data, new spacecraft, and the locations of currently
registered space crafts
Component-connector
notation
Summary of Event-Based Style
1.Independent Components
asynchronously emit and receive events
communicated over event buses
2.Components are independent
concurrent even generators and
consumers
3.Data elements are events sent as first
class entities over the event bus
Communicating Processes: ClientServer Architecture Style
OUTLINE
•
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
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Architectural Styles
Virtual Machines
2. Virtual Machines. Originated from the
concept that programs are treated as
data by a virtual machine, which is an
abstract machine implemented entirely
in software, that runs on top of the
actual hardware machine. Ex: rulebased style.
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Architectural Styles
Virtual Machines
Virtual Machines: The primary benefits are the
separation between instruction and implementation,
(Used when inputs are defined by a script and data)
Example: Java Virtual Machine. Java code translated to platform independent bytecodes. JVM is platform specific and
interprets (or compiles -JIT) the bytecodes.
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Virtual Machines Style
Virtual Machines Style Example
OUTLINE
•
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
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Architectural Styles
Data Flow
3. Data Flow. Include Batch Sequential Systems
(BSS) and Pipes and Filters (PF).
- BSS: different components take turns at
processing a batch of data, each saving the result of
their processing in a shared repository that the next
component can access. Ex. Dynamic control of physical
processes based on a feedback loop.
- PF: A stream of data processed by a complex
structure of process (filters). Ex, UNIX.
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Architectural Styles
Data Flow: Control Loop and Pipes and Filters
Control Loop
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BSS Architecture Style Example
BSS Style Summary
PF Example
concurrency between components (Filters) is allowed
PF example in Embedded Systems
concurrency between components (Filters) is allowed
A Robotics Example
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PF Another Architecture Example:
Watch for the Two Views
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PFs Style Summary
OUTLINE
•
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
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Data-Centered Architectural Styles
4. Data-Centered Systems. Consist of having
different components communicate
through shared data repositories. When
data repository is an active repository that
notifies registered components of changes
in it then-blackboard style.
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Data-Centered Architectural Styles
Repository Architecture Style
Data-Centered Architectural Styles
Repository Architecture Example: CASE Tools
Example
Data-Centered Architectural Styles
Repository Architecture Example: Compiler
Architecture
Data-Centered Architectural Styles
Blackboard Architecture Style: Components
perusing shared data, and communicating through it.
Used in Database intensive systems
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Data-Centered Architectural Styles
Blackboard Architecture Style Example
Compare with the PFs Style
Data-Centered Architectural Styles
Blackboard Architecture Style: Intelligent
Agent Systems Example
Data-Centered Architectural Styles
Blackboard Architecture Style:
Travel Counseling System Example
Data-Centered Architectural Styles
Blackboard Architecture Style: Intelligent Agent
Systems Example
Blackboard Architecture Style: Intelligent
Agent Systems Example
Data-Centered Architectural Styles
Blackboard and Publish/Subscribe Styles:
Intelligent Agent Systems Example
Blackboard Architecture Style
Rule-Based or Expert System
Architecture Style: Three components, a user
interface, an inference engine, and a knowledgebase
Rule-Based or Expert Systems Style
OUTLINE
•
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• SW Systems Mix of Architecture Styles
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Architectural styles
Call-and Return Family
5. Call-and Return Architectures. Due to heir simple
control paradigm and component interaction
mechanism , these architectures have dominated the
SW landscape by the early decades of the SW Eng.
• There are several styles within this family: examples
are main program and subroutine, and layered
architectures.
-) Main Program and Subroutine Style. Programs
are modularized based on functional decomposition,
single thread of control held by the main program,
which is then passed to subprograms, along with
some data on which the subprograms can operate.
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Main Program and Subroutine Style
Register.exe
Course registration
System example
PeopleInfo
CourseInfo
Course
StudentInfo
CourseOffering
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ProfessorInfo
Call-and Return Architectural styles
-) Layered. Functionality is divided into layers of abstractioneach layer provides services to the layer(s) above it, and
uses the services of layer(s) below it. In its purest form,
each layer access only the layer below it, but does not
depend on lower layers.
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Based on general systems
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Architecture, Network
Architectures, etc.
Layered Architectural styles
Example of a Layered Application Architecture
Layered Architectural styles
Example: Interactive Electronic Technical
Manual Layered Architecture
IETM Electronic Display
System (EDS)
IETM Data
Data Access
Data Layer
Business Layer
User Interface
Presentation
Layer
Layered Architectural styles
A Robotics Architecture
The Reactive Layer contains basic skills of the robot such as grasping an object and behavior that
must execute immediately in response to inputs from sensors. The Sequencing Layer combines
functions in the reactive layer into more complex behavior. The Planning Layer performs slower
Long-term planning
OUTLINE
•
Introduction
• Software Architecture Styles
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• SW Systems Mix of Architecture Styles
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SW Systems-Mix of Architecture Styles
• Most SW systems use a mix of architecture
styles. Ex, personnel management system
with a scheduling component, implemented
using the independent component style,
and a payroll component, using the batch
sequential style.
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SW Systems-Mix of Architecture Styles
Quality Attributes tradeoffs
• Choosing a style to implement a particular system
depends on several factors based on stakeholders
concerns.
• The typical factors concern the level of quality
attributes that each style enables us to attain. EX,
event-based systems-achieve very high level of
evolvability, at the expense of performance and
complexity.
• Virtual-machine style-achieve very high level of
portability, at expense of performance and perhaps
even testability.
SW Systems-Mix of Architecture Styles
Components of each Layer use different architecture styles
SW Systems-Mix of Architecture Styles
OUTLINE
Introduction
• Software Architecture Styles
•
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
•
SW Systems Mix of Architecture Styles
• Other Important Styles
• Buffered Massage-Based
• Model-View-Controller
• Presentation-Abstraction-Control
• Broker Architecture Style
• Service Oriented Architecture (SOA)
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• Peer-to-Peer Architecture
Software Architectures
Buffered Massage-Based Software
Architecture Style
In the J2EE Paltform,
• Java Massage Server (JMS) ia an API thatprovides
Asynchronous massage queuing mechanism
• Massage Driven Bean (MDB) is a special type of EJBs that
consumes asynchronous massages
Buffered Massage-Based Software
Architecture Style
Clients can publish massages on the JMS and MDBs register with the JMS
to receive Certain massage topics (asynchronous massage based
publish/subscribe).
Buffered Massage-Based Software
Architecture Style
• The MDB plays the role of a massage listener
It can connect remote Session EJBs or Entity EJBs
Web Application Example
Massage-Based Architecture Style
consists of three types of components
Massage-Based Architecture Style
Massage-Based Architecture Style
OUTLINE
Introduction
• Software Architecture Styles
•
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• Other Important Styles
•
•
•
•
•
•
Buffered Massage-Based
Model-View-Controller
Presentation-Abstraction-Control
Broker Architecture Style
Service Oriented Architecture (SOA)
Peer-to-Peer Architecture
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Model-View-Controller Architecture Style
• The Controller manipulates the data Model
• The View retrieves data from the model and
displays needed information
Model-View-Controller Architecture Style
Dynamic Interactions
Model-View-Controller Architecture Style
Web Applications Java-based Implementation Example
OUTLINE
Introduction
• Software Architecture Styles
•
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• Other Important Styles
•
•
•
•
•
•
Buffered Massage-Based
Model-View-Controller
Presentation-Abstraction-Control
Broker Architecture Style
Service Oriented Architecture (SOA)
Peer-to-Peer Architecture
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Presentation-Abstraction-Control
Agents Architecture Style
•
•
•
•
•
Based on MVC Style but geared towards agent-oriented Systems
Consists of a Hierarchy of Agents, each agent with a P, A, and C components
The C component in each agent is in charge with communicating with other agents
The top-level agent is in charge of the core data and business logics
Lower-Level Agents provides detailed data and presentation
Presentation-Abstraction-Control
Agents Architecture Style Example
• Simple Presentation Application that can display
Pages of a presentation
• Consists one a top-level agent 1 and four lower level
agents
• Agent 1 have access to the pages,
and the other agents respond to
user requests for first, previous, next
and last pages
A scenario capturing
the event of pressing
the next button
Presentation-Abstraction-Control Style
Presentation-Abstraction-Control Style
PAC Style vs MVC Style
OUTLINE
Introduction
• Software Architecture Styles
•
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• Other Important Styles
•
•
•
•
•
•
Buffered Massage-Based
Model-View-Controller
Presentation-Abstraction-Control
Broker Architecture Style
Service Oriented Architecture (SOA)
Peer-to-Peer Architecture
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Broker Architecture Style
Brokers gets requests from client proxies and manages them by forwarding to server
Proxies or dispatches them to other connected brokers
Broker Architecture Style
Broker Architecture Style
Broker Architecture Style
Example: CORBA, Common Object
Request Broker Architecture
Client-Side Proxy
IDL
Server-Side Proxy
(IDL)
Example: CORBA, Common Object
Request Broker Architecture
OUTLINE
Introduction
• Software Architecture Styles
•
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• Other Important Styles
•
•
•
•
•
•
Buffered Massage-Based
Model-View-Controller
Presentation-Abstraction-Control
Broker Architecture Style
Service Oriented Architecture (SOA)
Peer-to-Peer Architecture
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Service Oriented Architecture (SOA) Style
Makes use of an Enterprise Service Bus ESB
Used in web-based systems and distributed computing
The SOA Style
Before
SOA
nodes make resources available to other
participants in the system as independent services that
the participants access in a standardized way using the ESB
Service Oriented Architecture (SOA) Style
A Map of SOA Components
Registry and Repository
Manage and monitor
Security
Web Portals
Human Business Process Management (BPM)
Enterprise Service Bus (ESB)
Data Services
Process Services
Business Logic
Orchestration
System BPM
The ESB Performs:
• data transformation
• Intelligent routing
• Real time monitoring
• Exception handling
• Service security
Databases
Systems of Record
Cloud Services Architecture
SOA supports Cloud Computing Models
Cloud Services Architecture
Human as a service, Software as a service, Infrastructure as a service
OUTLINE
Introduction
• Software Architecture Styles
•
•Independent Components
• Virtual Machines
• Data Flow
• Data-Centered
• Call-and return
• Other Important Styles
•
•
•
•
•
•
Buffered Massage-Based
Model-View-Controller
Presentation-Abstraction-Control
Broker Architecture Style
Service Oriented Architecture (SOA)
Peer-to-Peer Architecture
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Peer-to-Peer Architecture Style
Peer-to-Peer Architecture Style
The Gnutella Example
• Pure Peer-to-Peer
Architecture
• A sends query for a data
resource to neighbors B and H,
they pass it on until the peer having
the resource is found or until
a certain threshold of hops
is reached
Peer-to-Peer Architecture Style
The Gnutella Example
Recent Versions of Gnutella supports two types of peers Ultra peers and Leaf peers
Ultra peers runs in systems with fast internet connects and are responsible for request routing
and responses, they are connected to a large number of other Ultra peers and leaf peers,
while the leaf peers are connected to a small number of Ultra peers
Peer-to-Peer Architecture Style
The Skype Example
• A mixed client-Server and Pee-to-Peer
• Skype Peers get promoted to a supernode
status based on their network connectivity
And machine performance
• Supernodes perform the
Communication and routing
of massages to establish a call
• When a user logs in to the server
he is connected to a supernode
• If a peer becomes a supernode
he unknowingly bears the cost of routing
a potentially large number of calls.
Peer-to-Peer Architecture Style
The Skype Example
Conclusions
• An architectural style is a coordinated set of
architectural constraints that restricts the
roles/features of architectural elements and
the allowed relationships among those
elements
• Choosing a style to implement a particular
system depends on several factors based on
stakeholders concerns and quality attributes
• Most SW systems use a mix of architecture
styles