Transcript Software Architectural Styles

Software
Architectural Styles
Andrew Midwinter, Mark Mullen, Kevin Wong, Matt Jones
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What is Software Architecture?
• Provides a very high level view of the
parts of the system and how they are
related to form the whole system.
• More specifically, architecture
partitions the system in logical parts
such that each part can be
comprehended independently and
then describes the system in terms of
these parts and their relationships.
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Some Examples…
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Client-Server
Event-Driven
Peer-to-peer
Pipes and Filters
Three-Tier
Service-Oriented
Monolithic
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Blackboard
Implicit Invocation
Plug-in
Search-Oriented
Distributed Computing
Cloud Computing
Front end and Back end
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What Software Architecture is not
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Design patterns
Low-level design
Implementation
Computer Architecture
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Design vs. Software Architecture
• Architecture deals with “what” and
“where” whereas design deals with
the “how”
• Design patterns are to design as
architectural styles are to
architecture
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Event-Driven Architecture
• Very common architecture
• Three main components:
• The Event
• The Event Bus
• The Listener
Figure 1: Block Diagrams for Event Driven Applications
(Li, 2005)
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The Event
• Something that happens, either inside or outside the system,
that causes some kind of action in the system.
• Most of the time it is an external input, such as input from a
keyboard or controller, or sensors.
• Can also be other processes.
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The Event Bus
• The connector between events and listeners.
• Performs event-stream-analysis, which includes data cleansing
and normalization.
• Propagates events to the listeners connected to them.
• Also handles listener registration.
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The Listener
• An object that
executes some
function when a
specific event occurs.
• Registers its interest
in certain events
through the event
bus.
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Pros and Cons
• Pros:
• Analysis of events and actions related to them are done quickly.
• Very good for systems that need to be able to respond to external
events.
• Cons:
• More complex programs: can be difficult to follow the flow of a
system.
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Uses
• Graphical User Interfaces
• Swing
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Financial Trading systems
Pipeline monitoring systems
Sensor networks
Heart Rate Monitors
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Client-Server Architecture
• Very common type of
architecture
• Used in computer networking
• Some example protocols : DNS,
FTP, SMTP, HTTP
• Three main Components:
• The Client
• The Server
• A Network
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The Client
• Usually a personal computer
• Connects to a server, makes a request
• Receives a reply, makes more requests, etc.
• Often accesses the server through an application
• There are several different kinds of clients
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The Server
• A computer program running to serve the requests of other
programs
• Often performs computational tasks for the clients
• There are several different types
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Pros and Cons
• Pros:
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Performance
Simplicity (for clients)
Accessibility
Scalability
• Cons:
• Cost
• Overloading
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3-Tier
• Was developed by John J. Donovan in Open Environment
Corporation (OEC)
• User interface, process logic, computer data storage and data
access are developed and maintained as independent
modules, often on separate platforms
• Eg) a change of an OS may want only to change the
presentation layer would only affect the UI code (Windows 8?)
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3-Tier
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Example: Siri?
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Peer-to-Peer
• P2P is a network architecture in which each computer has
equivalent capabilities and responsibilities. (Miller, 2001)
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A better definition
• 5 Characteristics:
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Computers connect to each other in real-time
Peers are both clients and servers
Primary content is provided by peers
Peers are autonomous and control their own activities
Peers are not necessarily permanent and many connect and
disconnect at will
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Three forms
• Pure
• Centralized
• Hybrid
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Pros and Cons
• Pros
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Speed
Reliability
Availability
Privacy
Scalability
• Cons
• Security
• No mediator
• Unavailability
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Monolithic
• A somewhat older style of
architecture, not used as often
now
• Everything is compiled and
linked into a single application
• Many programs we deal with
day-to-day use it (sort of):
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Word processors
Powerpoint
Older mainframes
Development Environments
Older accounting software
Some Games
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Monolith – In Programming
• Usually written in a single
programming language
• Can operate in both batch
mode or GUI mode
• Can have concurrency:
• Multi-threading
• Multi-Processing
• But only one executable!
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Pros and Cons
• Pros
• Performance
• Simplicity
• Cons
• Problems with shared access
• Quantity of Data
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Summary
• Architectural styles are used in
most applications today
• They implement standards that
can be reused
• These standards make it easier to
make early design decisions
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Questions?
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