Software Architecture

Transcription

1 Software Architecture Quiz with Explainations Hans-Petter Halvorsen, M.Sc.

2 Questions 1. Explain 3-layer Architecture 2. What is a Web Service? 3. What is SOA? 4. What is an API? 5. What is Client-Server Architecture? 6. What is a Presentation Layer? 7. What is a Business Layer? 8. What is a Data Layer? 9. What is the main purpose with 3-layer/n-tier architecture? 10. List the different parts in Web Services (SOAP)?

3 Explain 3-layer Architecture

4 n-tier/3-tier In software engineering, multi-tier architecture (n-tier architecture) is a client server architecture in which presentation, application processing, and data management functions are logically (and/or physically) separated. 3 layers are most used.

5 3-tier Architecture Presentation Layer Business Logic Layer Data Access Layer Data Source Note! Different Litterature may use different Names for the Layers

6 Client/Presentation Layer/Tier Business/Logic Layer/Tier Data Layer/Tier Note! Different Litterature may use different Names for the Layers Note! The different layers can be on the same computer (Logic Layers) or on different Computers in a network (Physical Layers)

7 What is a Web Service?

8 Problem How to Share Data between Devices in a Network? Server(s) Firewalls Security Local Network/Intern et Clients Routers/Switches, etc. Database

9 Problem How to Share Data between Devices in a Network? Database Clients Direct Connection between the Database and the Clients that need the Data is normally not possible, due to security, compatibility issues, etc. (Firewalls, Hacker Attacks, etc.) Direct Connection in a Local Network (behind the Firewall) is normally OK but not over the Internet.

10 Solution: Web Service Web Service Internet HTTP Clients Database Web Services uses standard web protocols like HTTP, etc. HTTP is supported by all Web Browser, Servers and many Programming Languages 10

11 Client Client Client Data Web Services: A Standard way to get data over a network/internet Using standard Web protocols Server Data Network/Intern et Web Service Web Server Data Data Web Services Data Database Normally you dont have direct access to a Database over a network, and espesially not over Internet

12 Web Services A Web service is a method of communications between two devices over the World Wide Web. Web API Standard defined by W3C Cross-platform Web Services can be implemented and used in most Programming Languages (C#/ASP.NET, PHP, LabVIEW, Objective- C, Java,...) Uses standard Web technology (Web protocols) HTTP, REST, SOAP, XML, WSDL, JSON,...

13 Why Web Service? Today Web Services have been very popular Easy Data sharing over Internet Platform-independent Communication Makes it possible of integration of different systems and platforms Distributed Application Development Web Service Internet HTTP Clients

14 Web Services Web Services 1.0: Uses SOAP Complex Web Services 2.0: Uses REST Less Complex than using SOAP Lightwight and Flexible The prefered model today

15 The database-centric style. Typically, the clients communicate directly with the database. A three-tier style, in which clients do not connect directly to the database. Web Services, etc. 15

16 What is SOA?

17 SOA Service Oriented Architecture. Distributed Application Development Typical example: Web Services

18 What is an API?

19 API API - Aplication Programming Interface A specification of how some software components should interact with each other. A library with functions, etc. you can use in your code Examples: Windows API Java API But you can also create your own API that you use internally in the team or expose to others

20 Software Design without APIs Pros: Fast to implement in small projects. Agile can serve as a starting point for API design. No need to consider how code interfaces with other software. Can be appropriate for small dead end projects. Cons: Inappropriate for large projects. Code has a limited (as opposed to general) functionality. Code is not reusable. Code is hard to maintain/modify. Prone to errors and bugs.

21 Why a Good API is hard to Design Forces designer to anticipate future usage of code. Requirements are incomplete (may never be complete). Requires abstraction. Requires modularization. Requires skills in programming languages. Requires code rewrites time consuming and labor intensive.

22 The Benefits of API Driven Design When an API is used in a project, it Allows to focus on the project. Saves development time. Reduces errors and debugging. Facilitates modular design. Provides a consistent development platform. è API driven design requires planning and programming skills. API driven design is costly initially, but it pays in the long run. So, obviously, creating APIs is good software practice in most cases.

23 API

24 What is Client-Server Architecture?

25 Client-Server Client 2-layer architecture Response Server Request Data Storage

26 Client Client-Server Example Web Browser Response Web Server Request Database Internet Information Services (IIS)

27 What is a Presentation Layer?

28 Presentation Layer Typical the Graphical User Interface

29 What is a Business Layer?

30 Presentation Layer Typical the Business Logic, which handle the data between the User Interface and the Database. A Web Service is typically implmented in this layer.

31 What is a Data Layer?

32 Presentation Layer Typical the Database

33 What is the main purpose with 3-layer/n-tier architecture?

34 Why 3-tier? Decoupling They (the layes/tiers) can be developed and tested seperately.

35 List the different parts in Web Services (SOAP)?

36 SOAP Web Services WSDL (API Description) SOAP (Messaging) XML (Data) WSDL - Web Services Description Language SOAP - Simple Object Access Protocol XML Extensible Markup Language HTTP - Hypertext Transfer Protocol HTTP (Transport)

37 SOAP vs. REST SOAP: A service architecture WSDL (API Description) XML based SOAP (Messaging) Runs on HTTP but envelopes the message XML (Data) Slower than REST Very mature, a lot of functionality HTTP (Transport) Not suitable for browser-based clients More complicated REST: WADL (API Description) A service architecture Uses the HTTP headers to hold meta information REST (Messaging) Can be used with XML, JSON or whatever necessary XML/JSON(Data) Usually used with JSON due to the easily parsable content HTTP (Transport) Faster than SOAP

38 References Software Development - A Practical Approach Halvorsen, Hans-Petter, 2015 Essentials of Software Engineering Frank Tsui; Orlando Karam; Barbara Bernal, 3 ed., Jones & Bartlett Learning Software Engineering I. Sommerville, 10 ed.: Pearson, 2015 Software Engineering. Modern Approaches E. J. Braude and M. E.Bernstein, 2 ed.: Wiley, 2011.

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40 Hans-Petter Halvorsen, M.Sc. University College of Southeast Norway Blog: