CS计算机代考程序代写 database Java finance SE457 Week 1 – Introduction and Overview Part 1

SE457 Week 1 – Introduction and Overview Part 1
Steven Engelhardt
DePaul University
Spring 2021
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Table of Contents
1 Course Introduction
2 Personal Introductions
3 Introduction to Service-Oriented Architecture What is Software Architecture?
What is Service-Oriented Architecture? Goals and Challenges of SOA
Myths of SOA
4 Class Exercise
5 Service-Oriented Analysis and Design
6 Service Contracts
7 Service Coupling
8 Wrap-Up
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Course Objectives
• Introduce you to the latest developments in the area of service oriented architecture (SOA).
• Expose you to a broad range of topics with SOA as their common focus.
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Learning Objectives
• Understand the principles of service-oriented design
• Explain how the service-oriented design paradigm differs from other
design approaches
• Design preliminary service-oriented architectures which take into consideration quality goals such as reliability, performance, and scalability
• Implement a web service using modern techniques
• Evaluate the coming attractions in service-oriented architecture
research and practice
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Limitations
• This course is a survey course, which means that it does not go into great depth on any given subject.
• This is not just a web services class although we will discuss them.
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Primary Textbook
Thomas Erl. SOA: Principles of Service Design. Prentice-Hall, 2008. ISBN: 0-13-234482-3.
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Secondary References
•
Newman, Sam. Building Microservices: Designing Fine-Grained Systems. 1st : O’Reilly Media, 2015.
Rotem-Gal-Oz, Arnon. SOA Patterns. Shelter Island, NY: Manning Pubications Co., 2012.
•
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Communication Plan
• My office hours are from 16:00 – 17:30 before class, online-only via Zoom
• Email is the best way to contact me: sengelha@depaul.edu
• All notes, handouts, assignments, grades, etc. will be available
through D2L. Please do not email me your assignments.
• Course homepage: https://d2l.depaul.edu/d2l/home/811041
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Prerequisites
• SE450 or CSC435
• Some Java programming will be required
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Quizzes
• There will be 5 quizzes
• Quizzes are generally due alternate Tuesdays at 5:30PM (right before
class)
• Each quiz will allow up to 5 attempts
• Resubmission attempts will only include wrong answers
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Homework
• There will be 5 homework assignments
• Homework will be a combination of theory and practice
• There is some Java coding in this class
• Assignments are generally due alternate Tuesdays at 5:30PM (right before class)
• Late homework will not be accepted without strong justification
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Research Presentation
• Each student will submit a research presentation on some aspect of SOA.
• Topics need to be approved by the instructor by week 3 (April 13).
• Research presentations are to be submitted as 20-30 minute long
YouTube videos by week 10 (June 1)
• More details are available on D2L.
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Exams
• There is no midterm
• There will be an open book final exam. It will be available on D2L as
a quiz during final exam week (June 5 – June 11).
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Grades
Quizzes
Quiz 1 4% Quiz 2 4% Quiz 3 4% Quiz 4 4% Quiz 5 4%
Homework 40% HW1 5% HW2 5% HW3 10% HW4 10% HW5 10%
Research Presentation 20% Final Exam 20%
Total 100%
20%
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Course Outline
Unit 1: Overview and Principles Introduction to SOA
Design Principles
Unit 2: Implementation Approaches SOAP
REST
gRPC
Unit 3: SOA Patterns Unit 4: SOA in Practice
Deployment Governance Monitoring Planning Security Testing
Final Exam
Total
2 weeks 2 weeks
2 weeks 4 weeks
1 week
11 weeks
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Important Due Dates
Assignment
Student Introductions
Quiz 1
Homework 1
Research Presentation Topic Approval Quiz 2
Homework 2
Quiz 3
Homework 3
Quiz 4
Homework 4
Quiz 5
Research Presentation Homework 5
Final Exam
Due Date
April 6 April 6 April 13 April 13 April 20 April 27 May 4 May 11 May 18 May 25 June 1 June 1 June 8 June 11
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Related Courses
• SE456 – Architecture of Real-Time Systems (typically offered Winter quarter)
• SE480 – Software Architecture I (typically offered Fall quarter)
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About Me
• Over 21 years of software engineering experience in varied roles
• Current role: Principal Engineer at Relativity responsible for the data services behind RelativityOne
• Previous roles:
• Chief Data Officer at Fi360
• 14 years at Morningstar, ending as Distinguished Engineer • Research Programmer at NCSA
• Software Development Engineer at Microsoft
• Education: M.S. Computational Finance from DePaul, B.S. Computer Engineering from UIUC
• CFA Charterholder
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About You
• One-by-one, introduce yourself over Zoom and why you decided to take this course
• Please turn on your camera during the introduction if you have one
• Asynchronous students: Please post an introduction on the Introduce
Yourself Here topic in D2L (due April 6 5:30PM)
• This is also how I take DePaul-required attendance
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Architecture is…
The software architecture of a program or computing system is the structure or structures of the system, which comprise software components, the externally visible properties of those components, and the relationships between them.
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Design Reflects Architecture
Architecture can be thought of as the earliest set of design decisions. These decisions can:
• Constrain implementation.
• Dictate organizational structure.
• Inhibit or enable systemic qualities.
• Facilitate reasoning about and managing change.
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An Architecture Must Answer These Questions
• What requirements are the structuring and decisions based on?
• Which are the major logical and physical system building blocks?
• How are the system building blocks related to one another?
• What responsibilities do the system building blocks have?
• What interfaces exist to the system building blocks?
• How are the system building blocks grouped or layered?
• What are the specifications and criteria used to divide the system into building blocks?
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Why Architecture Matters
• An architecture will inhibit or enable a system’s driving quality attributes
• Performance, modifiability, security, scalability, reusability, etc.
• Allows you to reason about and manage change as the system evolves
• Local, nonlocal, architectural changes
• Defines a set of constraints on subsequent implementation
• Performance budgets, restricting design alternatives to focus on implementation
• Dictates the structure of an organization, or vice versa (Conway’s Law) and helps allocate work
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Why Architecture Matters
• An architecture will inhibit or enable a system’s driving quality attributes
• Performance, modifiability, security, scalability, reusability, etc.
• Allows you to reason about and manage change as the system evolves
• Local, nonlocal, architectural changes
• Defines a set of constraints on subsequent implementation
• Performance budgets, restricting design alternatives to focus on implementation
• Dictates the structure of an organization, or vice versa (Conway’s Law) and helps allocate work
• Enables evolutionary prototyping
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Why Architecture Matters
• An architecture will inhibit or enable a system’s driving quality attributes
• Performance, modifiability, security, scalability, reusability, etc.
• Allows you to reason about and manage change as the system evolves
• Local, nonlocal, architectural changes
• Defines a set of constraints on subsequent implementation
• Performance budgets, restricting design alternatives to focus on implementation
• Dictates the structure of an organization, or vice versa (Conway’s Law) and helps allocate work
• Enables evolutionary prototyping
• Allows architects and project managers to reason about cost and
schedule
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Why Architecture Matters
• An architecture will inhibit or enable a system’s driving quality attributes
• Performance, modifiability, security, scalability, reusability, etc.
• Allows you to reason about and manage change as the system evolves
• Local, nonlocal, architectural changes
• Defines a set of constraints on subsequent implementation
• Performance budgets, restricting design alternatives to focus on implementation
• Dictates the structure of an organization, or vice versa (Conway’s Law) and helps allocate work
• Enables evolutionary prototyping
• Allows architects and project managers to reason about cost and
schedule
• Allows incorporation of independently developed components
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Why Architecture Matters
• An architecture will inhibit or enable a system’s driving quality attributes
• Performance, modifiability, security, scalability, reusability, etc.
• Allows you to reason about and manage change as the system evolves
• Local, nonlocal, architectural changes
• Defines a set of constraints on subsequent implementation
• Performance budgets, restricting design alternatives to focus on implementation
• Dictates the structure of an organization, or vice versa (Conway’s Law) and helps allocate work
• Enables evolutionary prototyping
• Allows architects and project managers to reason about cost and
schedule
• Allows incorporation of independently developed components
• Foundation for training of new team members
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SOA is…
• A style of software design where services are provided to the other components by application components, typically through a communication protocol over a network.
• It integrates distributed, separately maintained and deployed software components (services).
• Arguably the most common architectural form practiced today
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A service is…
• A discrete unit of functionality that can be accessed remotely and acted upon and updated independently, or…
• A collection of self-contained business functionality that exist as applications with their own design characteristics that support the strategic goals of the organization.
• A service has four properties according to one of many definitions of SOA:
1 It logically represents a business activity with a specified outcome.
2 It is self-contained.
3 It is a black box for its consumers, meaning the consumer does not
have to be aware of the service’s inner workings.
4 It may consist of other underlying services.
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What is a web service?
• In the general form, a web service is a service offered by an electronic device to another electronic device, communicating with each other via the World Wide Web (HTTP/HTTPS)
• The phrase “web service” is often closely identified with a particular technology suite, namely WSDL and SOAP, which have mostly fallen out of favor
• In this course, when I use the term “web service”, I almost always mean the more general usage of the term
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What is a microservice?
• Microservices are small, autonomous services that work together.
• Microservice architecture is a variant of the service-oriented architecture (SOA) structural style where services are fine-grained and the protocols are lightweight.
• Some people believe “SOA” solely refers to out-of-favor SOAP and WSDL-based web services, and consider microservices a radical alternative. I, however, consider microservices merely a way in which one may practice SOA.
• We will discuss microservices more later in this course.
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Classifying services
A simple, and occasionally useful, way of classifying services is into three types:
1 An entity service is a service whose functional boundary is related to one or more business entities.
2 A task service is a service whose functional boundary is related to one or more business processes.
3 A utility services is a service whose functional boundary is non-business-centric.
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How does SOA differ from other architectural styles?
• Service-oriented architecture was largely created as a response to traditional, monolithic approaches to building applications. SOA breaks up the components required for applications into separate service modules that communicate with one another to meet specific business objectives.
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Another example SOA
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SOA Principles
• Abstraction: The services act as black boxes, that is their inner logic is hidden from the consumers.
• Autonomy: Services are independent and control the functionality they encapsulate, from a Design-time and a run-time perspective.
• Composability: Services can be used to compose other services.
• Discoverability: Services are supplemented with communicative meta data by
which they can be effectively discovered and interpreted.
• Longevity: Services should be designed to be long lived. Where possible services should avoid forcing consumers to change if they do not require new features, if you call a service today you should be able to call the same service tomorrow.
• Reusability: Logic is divided into various services, to promote reuse of code.
• Standardized service contracts: Services adhere to a standard communications agreement, as defined collectively by one or more service-description documents within a given set of services.
• Statelessness: Services are stateless, that is either return the requested value or give an exception hence minimizing resource use.
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The goals of SOA include…
• Help businesses respond more quickly and more cost-effectively to changing market conditions
• Promotes the decoupling of services from consuming projects to encourage good design
• Simplify testing by limiting the scope which needs to be tested on a change
• Increase intrinsic operability by allowing nearly any programming language or platform to act as a service client
• Increase federation by allowing services to maintain autonomy and self-governance
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SOC is challenging
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Service orientation is complex…
• NFRs may become more complex and difficult to maintain due to reuse.
• Services must be designed to scale and cluster.
• The approach to service contract versioning and the support of different contracts must be defined.
• This is a topic addressed as part of governance.
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Standards are essential…
• Standards help provide consistency to architecture and design decisions.
• Introducing standards into siloed environments can be challenging.
• A champion is critical for the widespread adoption of standards.
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Service delivery speed is typically sacrificed…
• The speed of service delivery is often sacrificed to improve the speed of solution delivery.
• It takes more effort to identify, design, and build services than it does to implement equivalent non-service-oriented logic.
• This can be a hard sell.
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Strong governance is critical…
• We must identify who “owns” particular services.
• May require alterations to the overall organizational, departmental, and team structures to facilitate the new delivery model.
• Having a senior sponsor at the appropriate level is critical to success.
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Service-orientation has some myths
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SOA is evolutionary…
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…not revolutionary
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Enterprise-wide standardization is required
• Service-orientation derives its biggest benefit when standardization occurs at the greatest scale possible.
• It’s only required at a meaningful extent for value to be derived.
• Standardization helps avoid problems and ensures the greatest benefit.
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Reuse is a requirement
• While reuse is a significant benefit of service-oriented computing, it isn’t the only one.
• Of equal, possibly even greater, importance is the interoperability achieved by allowing systems to interoperate in a standard way.
• Interoperability alone can result in a significant ROI.
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Class Exercise
• Amazon’s retail website is built using SOA.
• What do you think are some of the services behind the website?
• How do you think these services might interact?
• What might be some unique challenges they face?
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What’s a service inventory?
• An independently standardized and governed collection of complementary services within the boundary of an enterprise or meaningful segment of an enterprise.
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Inventory analysis builds a blueprint for the service inventory
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Service-oriented analysis identifies the services to be added to the inventory
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Service modeling is where the real work happens
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Design the service contracts and implementations
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Principle
Short Version
• Services share standardized contracts.
Long Version
• Services within the same service inventory are in compliance with the same contract design standards.
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What’s a service contract?
• A service contract defines the terms of engagement, describing technical service descriptions and constraints.
• This is what any consumer needs to know about the service and its properties.
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Emphasis is on technical contracts…
• Service contracts always require at least one technical service description, but may also include other non-technical elements such as service level agreements (SLAs).
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There are non-technical contracts
• Service level agreements are the classic example. They address things like:
• Availability schedule
• Response times guarantees • Charge-back costs
• This kind of information can be captured in a service profile.
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Contracts have evolved…
Client-Server Model
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Distributed Model

…to where we now have web services
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• The emphasis here is going to be on the representation of the contract itself.

Standardization has benefits
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So what needs to be standardized?
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Service Capability Expression
• Makes services easier to understand and to design.
• Can help reduce the chances that redundant services will be constructed through ignorance or misunderstanding.
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Service Data Representation
• Many services, even those spanning teams, may work with identical data.
• This means that to be most effective, the teams need to have a similar view of the service data.
• This often requires hand-crafted representations rather than automatically generating them from code.
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Service Policies
• Policies about the service can be declared separately from the service itself.
• Some of these policies are defined by other standards.
• Policies can be customized on a per-service basis while allowing for common aspects to be centralized.
• The integration of policy with contract can also be standardized.
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Data representation and transformation avoidance
• Contracts may not be standardized because:
• Auto-generation.
• 3rd party providers.
• Existing standards were
lacking.
• Existing standards were
ignored.
• Data transformation results in:
• Increased development effort. • Increased runtime overhead. • Increased complexity.
• Increased governance.
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Standardized service contracts can…
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Principle
Short Version
• Services are loosely coupled.
Long Version
• Service contracts impose low consumer coupling requirements and are themselves decoupled from their surrounding environment.
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What’s service coupling?
• Coupling is concerned with dependencies. Services with a high degree of coupling are more dependent on other, external resources, which can make them harder to change.
• High degrees of coupling can also force change when it isn’t wanted. For example, when an external resource changes.
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Coupling requires a careful balance
• Services need to be accessible to any consumer that wishes to use it, but…
• That same service must remain insulated so that the consumer knows only what they absolutely must know.
• This balance allows a service to evolve without breaking the consumers each time something changes.
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Emphasis is on the contract’s design
Steven Engelhardt (DePaul University)
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• In this case it isn’t how the contract is represented, but what the contract represents.
• Avoid exposing too much information about either the service logic or the runtime environment.

What kinds of coupling are possible?
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Service coupling is concerned with service design
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Logic-to-Contract coupling
• Logic-to-contract coupling reflects a “contract first” design approach.
• This is the preferred approach to designing service contracts since it helps ensure as much standardization as possible.
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Contract-to-Logic coupling
• Contract-to-logic coupling reflects an “implementation first” design approach.
• This typically happens when contracts are derived from or wrap an existing implementation.
• This is an SOA anti-pattern. It reflects the trade-off between rapid service implementation and slower solution implementation.
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Contract-to-Technology coupling
• Contract-to-technology coupling typically happens when there are proprietary communication transports involved.
• Examples include .NET remoting or Java RMI.
• These technologies may necessitate contracts changes to support the transport protocol.
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Contract-to-Implementation coupling
• Contract-to-implementation coupling typically happens when contracts are derived from implementations.
• For example, generating a contract from a database schema will often embed data model details into the contract.
• Minimizing this form of coupling improves autonomy.
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Contract-to-Functional coupling
• Contract-to-functional coupling
occurs when service logic is
designed to support functionality Examples include: that exists outside of the service.
• This isn’t always bad. For example, task services are intended to represent business processes and thus control the entire process.
• Parent Processes
• External Consumers
• Point-to-point integrations
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Consumer coupling is concerned with service access
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Consumer-to-Implementation coupling
• Consumer-to-implementation coupling occurs when a consumer does not use the service’s contract in favor of some other mechanism.
• This is an SOA anti-pattern. It reflects perceived trade-offs between using the contract with increased performance or simplicity.
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Consumer-to-Contract coupling
• Consumer-to-contract coupling occurs when a consumer uses only the published contract to access the service.
• This is the preferred approach to accessing services since it maintains the greatest autonomy of both.
• Multiple contracts can be provided if needed.
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Contract Centralization
• Contract centralization is an SOA design pattern that limits the choice of how to access a service to exactly one option: the contract.
• Remember that whatever coupling is exposed through the contract will apply to the consumer.
• Good contract design is critical in reducing coupling.
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Loose service coupling can…
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Assignments
• Quiz 1 is available on D2L. It is due Tuesday, April 6 at 5:30 PM.
• Homework 1 is available on D2L. It is due Tuesday, April 13 at 5:30
PM.
• Research presentation topic proposals are available on D2L. They are due Tuesday, April 13 at 5:30PM.
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Next Steps
• Read chapters 1-7 in the text.
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