t-4

1. Explain the term “distributed systems”, contrasting it from “distributed computing” 

Distributed computing is a field of computer science that studies distributed systems. A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another.The components interact with one another in order to achieve a common goal. Three significant characteristics of distributed systems are: concurrency of components, lack of a global clock, and independent failure of components.Examples of distributed systems vary from SOA-based systems to massively multiplayer online games to peer-to-peer applications.

2. Compare and contrast the standalone systems with distributed systems, providing examples for advantageous use of both 
standalone systems
A standalone device is any mechanism or system that can perform its function without the need of another device, computer, or connection. A perfect example of astandalone device is a copy or fax machine, as shown in the picture.
ex-:  (JAVA, .NET)
                         

distributed systems
A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another.
ex-: (HTML +CSS + JS + PHP)

           


3. Discuss the elements of distributed systems 

• Data stores (data bases) and Data 
• Theconfiguration of the above elements
• The components to share the computing resources ,increasing the processing power ,provide better user experience 
• The users to share data and other resources, such as documents and files 
• The engineers to have a centralized control
• Processing components 
• Data networksfor components to communicate

4. Identify different types of services, which can be gained from distributed systems, specifying the protocols used for them 

• Mail service SMTP, POP3, IMAP
• File transferring and sharing FTP
• Remote logging (telnet) 
• Games and multimedia RTP, SIP,H.26x
• Web HTTP

5. Identify examples for both browser-based and non-browser-based clients of distributed systems 

• The world wide web – information, resource sharing
• Clusters, Network of workstations
• Distributed manufacturing system (e.g.,automated assembly line)
• Network of branch office computers -Information system to handle automatic
• processing of orders
• Network of embedded systems
• New Cell processor (PlayStation 3)
• 

6. Discuss the characteristics of different types of Web-based systems, including the RiWAs 

non-browser-based client-components of RiWAs 

The  standard desktop  application development TTs like JAVA  or  .Net  and  related libraries/frameworks  can  be utilized  for  non-browser-based  client-components development. For DC development, these frameworks  may contain  their  own  tools  or  some  third-party 

frameworks/libraries can be incorporated. 

Browser-based  Client-Components  of RiWAs 

There  are  several  approaches  for  the  browser-based RiWAs, inherited  from RIAs. The  first approach, which is the proprietary plugin based approach, uses the technologies such as Adobe (former Macromedia) Flash/Flex [13], JAVA Applets,  or  MS  Silverlight  .  These  technologies  are enriched  with  utensils for  developing desktop  applications like rich GUIs. 

https://www.youtube.com/watch?v=9qwq01qggYo

7. Explain different architectures for distributed systems, explaining special features of each.
client-server (or two-tier) architecture
Two Tier application AKA Client-Server application.

The Two-tier architecture is divided into two parts:

1. Client Application (Client Tier)
2. Database (Data Tier)

Client system handles both Presentation and Application layers and Server system handles Database layer. It is also known as client server application. The communication takes place between the Client and the Server. Client system sends the request to the Server system and the Server system processes the request and sends back the data to the Client System

                      
3-tier architecture
Three Tier application AKA Web Based application

The Three-tier architecture is divided into three parts:

1. Presentation layer (Client Tier)
2. Application layer (Business Tier)
2. Database layer (Data Tier)

Client system handles Presentation layer, Application server handles Application layer and Server system handles Database layer.

                 

n-tier architecture
n-tier architecture is a client–server architecture in which presentation, application processing, and data management functions are physically separated.

Service Oriented Architecture (SOA) 
Service-oriented architecture (SOA) is a style of software design where services are provided to the other components by application components, through a communication protocol over a network. The basic principles of service-oriented architecture are independent of vendors, products and technologies.

                 

https://www.youtube.com/watch?v=L5BlpPU_muY

8. Compare and contrast the micro-service architecture from monolithic architecture 
micro-service architecture
micro service is a small application that has its own hexagonal architecture consisting of business logic along with various adapters.
monolithic architecture 
Micro services Architecture is to split your application into a set of smaller, inter connected services instead of building a single monolithic application. 

9. Explain the MVC style, indicating the limitations of it in the context of web-based systems 
MVC is Model-View-Controller Pattern.
This pattern is used to separate application's concerns. Model - Model represents an object or JAVA POJO carrying data.
Modularizing Styles

• Classic MVC

              

• client-side mvc

            

• client-mvc and server-mvc

                 

• MVC web version

                 

• BAW-MVC

   

10. Identify different approaches of use of MVC for web-based systems and discuss their strengths and weaknesses 

Model view controller (MVC) [1] is an architectural pattern usually used in web-based applications. It provides three main layers; model, view, and controller. Many developers use MVC as a standard design pattern. It is a complete framework. MVC provide three types of classes:

1. A. Model- Model classes are used to implement the logic of data domains. These classes are used to retrieve, insert or update the data into the database associated with our application.
2. View- Views are used to prepare the interface of our application. By using that interface users interact with our application.
3.  Controller- Controller classes are used to respond to the user’s requests. Controller classes perform the users requested actions. These classes work with model classes and select the appropriate view that should be displayed to the user according to user requests.

11. Discuss the need for very specific type of communication technologies/techniques for the distributed/web-based systems 
    1. Functional oriented communication 
             
    2. Message Oriented communication 
Message-oriented communication is a way of communicating between processes. Messages, which correspond to events, are the basic units of data delivered. ... In synchronouscommunication, the sender blocks waiting for the receiver to engage in the exchange.

    3. Resource oriented communication 
A resource-oriented architecture (ROA) is the structural design supporting the internet working of resources. A resource, in this context, is any entity that can be identified and assigned a uniform resource identifier .

12. Compare and contrast RPC with RMI 

RPC and RMI are the mechanisms which enable a client to invoke the procedure or method from the server through establishing communication between client and server. The common difference between RPC and RMI is that RPC only supports procedural programming whereas RMI supports object-oriented programming.

Another major difference between the two is that the parameters passed to remote procedures call consist of ordinary data structures. On the other hand, the parameters passed to remote method consist of objects

13. Explain the need for CORBA, indicating it’s use in web-based systems 
Common Object Request Broker Architecture
A software-based interface from the Object Management Group that allows software modules to communicate with each other no matter where they are located on a private network or the global Internet. CORBA is a "distributed objects" system designed for multi-tier, client/server applications, where processing data in one computer requires additional processing by some other service in another computer in order to complete the transaction.
         

14. Discuss the XML specification, highlighting the important sections such as element naming conventions 

XML stands for Extensible Markup Language. It is a text-based markup language derived from Standard Generalized Markup Language (SGML).

XML tags identify the data and are used to store and organize the data, rather than specifying how to display it like HTML tags, which are used to display the data. XML is not going to replace HTML in the near future, but it introduces new possibilities by adopting many successful features of HTML.

There are three important characteristics of XML that make it useful in a variety of systems and solutions −

• XML is extensible − XML allows you to create your own self-descriptive tags, or language, that suits your application.

• XML carries the data, does not present it − XML allows you to store the data irrespective of how it will be presented.

• XML is a public standard − XML was developed by an organization called the World Wide Web Consortium (W3C) and is available as an open standard.

XML Usage

A short list of XML usage says it all −

• XML can work behind the scene to simplify the creation of HTML documents for large web sites.
• XML can be used to exchange the information between organizations and systems.
• XML can be used for offloading and reloading of databases.
• XML can be used to store and arrange the data, which can customize your data handling needs.
• XML can easily be merged with style sheets to create almost any desired output.
• Virtually, any type of data can be expressed as an XML document.s

15. Compare and contrast XML and JSON, indicating the pros and cons of both 

JSON (JavaScript Object Notation) is a lightweight data-interchange format and it completely language independent. It is based on the JavaScript programming language and easy to understand and generate.

XML (Extensible markup language) was designed to carry data, not to display data. It is a W3C recommendation. Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The design goals of XML focus on simplicity, generality, and usability across the Internet. It is a textual data format with strong support via Unicode for different human languages. Although the design of XML focuses on documents, the language is widely used for the representation of arbitrary data structures such as those used in web services.

16. Identify other data formatting/structuring techniques available for the communication of web-based systems 

In a web-based learning environment communication can be either:

Synchronous- communication takes place at the same time. This requires that all participants are present at the same time. This type of communication is used fairly rarely for specific purposes such as getting acquainted, changing opinions, working in small groups, brainstorming etc.

Asynchronous- communication takes place at different times or over a certain period of time. This allows more time to work on your messages and to react to other students' messages.

Communication can vary also depending on the amount of people it involves. Communication on the web can be divided into the following types, involving a different amount of participants at a time:

One to one- one person communicates with somebody else, for example a student sends an A&O e-mail message to his/her trainer
One to many- one person communicates with many others, e.g. a student posts a message in A&O's discussion forum
Many to many- many persons communicate with each other, e.g. via videoconferencing

The most relevant tools for communication in the VERT courses you are about to take are the 
following:

Internet e-mail- The regular e-mail can be sent to the instructor or other students e.g. if there is something that needs immediate attention.
A&O's mail- This e- mail is dedicated to studying and stays in A&O virtual learning environment.
A&O discussion forum- A tool for asynchronous, one-to-many communication for many purposes.

References

• https://medium.com/koderlabs/introduction-to-monolithic-architecture-and-microservices-architecture-b211a5955c63
• https://ifs.host.cs.st-andrews.ac.uk/Books/SE9/Web/DistribSys/Corba.html

t-3

1. Discuss the importance of maintaining the quality of the code, explaining the different aspects of the code quality 

• Code quality matters in many ways
• Code is ,

              long-term usefulness
              long-term maintainability

• Minimize errors and easily debugged 
• Improve understandability 

 Impact of Quality code

• Efficiency

The goal of code efficiency is to reduce resource consumption and completion time as much as possible with minimum risk to the business or operating environment. The software product quality can be accessed and evaluated with the help of the efficiency of the code used

• Clarity

Clarity is an indicator of quality that says good code should be unambiguous. If you look at a piece of code and wonder what on earth it does, then that code is ambiguous.

This, along with readability and documentation,  means any other developer can easily use code written by someone else, without taking a long time to understand how it works.

• Maintainable

Code maintainability is a qualitative measurement of how easy it is to make changes, and the risks associated with such changes.

Developers can make judgments about maintainability when they make changes — if the change should take an hour but it ends up taking three days, the code probably isn’t that maintainable.

Another way to gauge maintainability is to check the number of lines of code in a given software feature or in an entire application. Software with more lines can be harder to maintain.

• Documented

f the program is not documented, it will be difficult for other developers to use it, or even for the same developer to understand the code years from now. One common definition of quality is that it may be “used long term, can be carried across to future releases and products” (without being considered “legacy code”). Documentation is essential to make this happen.

Documentation also provides a way to improve by formalizing the decisions you make when writing. When you document code and do it well, you need to think differently about each component and why it exists in the software. Writing out the reasons for certain programming decisions can improve application design.

• Well-tested

Well tested programs are likely to be of higher quality, because much more attention is paid to the inner workings of the code and its impact on users. Testing means that the application is constantly under scrutiny.


2. Explain different approaches and measurements used to measure the quality of code 

• Weighted Micro Function Points
• Halstead Complexity Measures 
• CyclomaticComplexity 
• Lines of code 
• Lines of code per method

3. Identify and compare some available tools to maintain the code quality 

  SonarQube

 It is an open source web-based tool, extending its coverage to more than 20 languages, and also allows a number of plugins 

Coverity

Coverity Scan is an open source cloud-based tool. It works for projects written using C, C++, Java C# or JavaScript. This tool provides a very detailed and clear description of the issues which helps in faster resolution. A good choice if you are looking for an open source tool

Code Compare

CodCode Compare – is a file and folder comparison and merge tool. Over 70,000 users actively use Code Compare while resolving merge conflicts and deploying source code changes. Code Compare is a free compare tool designed to compare and merge differing files and folders. Code Compare integrates with all popular source control systems: TFS, SVN, Git, Mercurial, and Perforce. Code Compare is shipped both as a standalone file diff tool and a Visual Studio extension.
Key features:

• Text Comparison and Merging
• Semantic Source Code Comparison
• Folder Comparison
• Visual Studio Integration
• Version Control Integration and moree Compare

GAMMA
Gamma is an intelligent software analytics platform, developed by Acellere. It supports developers and teams in building higher quality software in less time, by speeding up code reviews.

It automatically prioritizes hotspots in the code and provides clear visualizations. With its multi-vector diagnostic technology, it analyses software from multiple lenses, including software design, and enables companies to manage and improve their software quality transparently.
4. Discuss the need for dependency/package management tools in software development? 

Package managers automate the process of installing, upgrading, configuring, and removing computer programs from an operating system in a consistent manner. A package manager deals with ‘packages’ – distributions of software and data in archive files. Packages contain metadata, such as the software’s name, its purpose, version number, checksum and a list of dependencies necessary for the software to run properly. Upon installation, metadata is stored in a local package database. Package managers typically maintain a database of software dependencies and version information to prevent software mismatches and missing prerequisites. They work closely with software repositories, binary repository managers and app stores.

5. Explain the role of dependency/package management tools in software development 

Contemporary distributions of Linux-based operating systems install software in pre-compiled packages, which are archives that contain binaries of software, configuration files, and information about dependencies. Furthermore, package management tools keep track of updates and upgrades so that the user doesn’t have to hunt down information about bug and security fixes.

• Third party packages 
• External libraries 
• Plug-ins

These external artefacts may introduce many integration issues

• file structures and may use different ways of integrating into the main framework
• Different versions are available and difficult to upgrade

There are tools to manage these external artefacts..

• Composer [php ] 
• Maven [Java] 
• NuGet [.net] 
• NPM (Node Package Manager) [JS] 
• Bower [JS]

EX- Maven [Java] 

 Maven is a multi-purpose tool

Having a common directory layout would allow for users familiar with one Maven project to immediately feel at home in another Maven project. The advantages are analogous to adopting a site-wide look-and-feel.

The next section documents the directory layout expected by Maven and the directory layout created by Maven. Please try to conform to this structure as much as possible; however, if you can't these settings can be overridden via the project descriptor.

                         


6. Compare and contrast different dependency/package management tools used in industry 

Maven

 A repository in Maven holds build artifacts and dependencies of varying types.

There are exactly two types of repositories: local and remote. The local repository is a directory on the computer where Maven runs. It caches remote downloads and contains temporary build artifacts that you have not yet released

Yum

Yum is an automatic updater and package installer/remover for rpm systems. It automatically computes dependencies and figures out what things should occur to install packages. It makes it easier to maintain groups of machines without having to manually update each one using rpm. Yum has a plugin interface for adding simple features. Yum can also be used from other python programs via its module inteface.

NuGet

NuGet is the package manager for the Microsoft development platform including .NET. The open-source NuGet client tools provide users with the ability to produce and consume packages in a similar fashion to RedHat's yum, but with a software development focus. The central package repository for NuGet is known as the NuGet Gallery and is used by all package authors and consumers

Chocolatey

Chocolatey is a package manager for Windows. Designed as a decentralized framework for quickly installing applications and tools, it is built on the NuGet infrastructure and uses PowerShell to deliver packages. Chocolatey packages can be used independently, but also integrate with configuration managers like SCCM, Puppet and Chef.

7. What is a build tool? Indicate the 
significance of using a build tool in large scale software development, distinguishing it from small scale software development 

Build tools are programs that automate the creation of executable applications from source code. 

In small projects, developers will often manually invoke the build process. This is not practical for larger projects, where it is very hard to keep track of what needs to be built, in what sequence and what dependencies there are in the building process. Using an automation tool allows the build process to be more consistent.

The advantages of build automation to software development projects include

• A necessary pre-condition for continuous integration and continuous testing
• Improve product quality
• Accelerate the compile and link processing
• Eliminate redundant tasks
• Minimize "bad builds"
• Eliminate dependencies on key personnel

8. Explain the role of build automation in build tools indicating the need for build automation 

Main 3 types Build automation

• On-demand automation
• Scheduled automation 
• Triggered automation

    On-demand automation

   On-Demand Automation is how innovators like DHL Supply Chain meet customer               demands in an evolving workforce environment. On-Demand Automation enables distributors, manufacturers, and fulfillment centers to find, track and move anything in their facilities. On-Demand Automation means no limitations on workflow types

    Scheduled automation

Automated planning and scheduling, sometimes denoted as simply AI planning, is a branch of artificial intelligence that concerns the realization of strategies or action sequences, typically for execution by intelligent agents, autonomous robots and unmanned vehicles.

              

   Triggered automation

An automation that is initiated when a file is dropped into a designated Enhanced FTP Folder. B. An automation that is triggered based on a schedule that has been defined. C. An automation that is initiated when a designated value in a data extension is changed.

                         

9. Compare and contrast different build tools used in industry 

Maven
Apache’s Maven is a build automation tool primarily for Java projects, and is the most popular choice for Java developers today by the usage numbers. Unlike Apache Ant, it uses conventions for the build procedure, and only exceptions need to be written down.When to use it: If you want the de facto tool and plugin repository. If you’re running anything unusual with your other tools, Maven will support it. Well suited for large enterprises due to its very fast build speed.

Price: free

Pros:

• Extensive ecosystem for plugins.
• Common structure between builds makes understanding other projects easy.
• Full support for almost any CI, app server, or IDE tool.

Cons:

• Lots of download requirements for dependencies and plugins.
• Up and down documentation quality.
• Community is largely quiet.
• Customization is weak.

Gradle

Gradle is an open source build automation system. With version 1.0 released in 2012, Gradle aims to “combine the power and flexibility of Ant with the dependency management and conventions of Maven into a more effective way to build.” Its build scripts are written in Groovy, not XML, which creates a host of different advantages and disadvantages compared to Ant or Maven. Despite being a newer tool in this space, it’s seen widespread adoption.When to use it: Gradle is designed for multi-project environments and incremental builds. It’s good if you’re comfortable with Groovy or are willing to get there. It’s also great for personal projects and SMBs.

Price: free

Pros:

• DSL base means you have a more customizable and streamlined tool.
• No required build script boilerplate makes for a simpler experience.
• Excellent documentation and active community. For example, Gradleware is a company designed around facilitating the adoption and use of Gradle through consultancy and other guidance.
• It’s simple to create custom plugins.

Cons:

• DSL base means you have a less straightforward and standardized tool.
• As the new kid on the block, the ecosystem for plugins and the like is less developed.
• As a newer tool, its support for CI tools and app servers isn’t as fleshed out as Maven or Ant

10. Explain the build life cycle, using an example (java, .net, etc…) 

Maven is based around the central concept of a build lifecycle. What this means is that the process for building and distributing a particular artifact (project) is clearly defined.

For the person building a project, this means that it is only necessary to learn a small set of commands to build any Maven project, and the POM will ensure they get the results they desired.

There are three built-in build lifecycles: default, clean and site. The  lifecycle handles your project deployment, the  lifecycle handles project cleaning, while the lifecycle handles the creation of your project's site documentation.

The primary(default) life cycle of Maven is used to build the application

• Validate  
• Initialize  
• Generate-sources 
• Compile 
• Generate-test-sources 

    EX -:
      JAVA
            

    .NET
          

11. What is Maven, a dependency/package management tool or a build tool or something more? 

At first glance Maven can appear to be many things, but in a nutshell Maven is an attempt to apply patterns to a project's build infrastructure in order to promote comprehension and productivity by providing a clear path in the use of best practices. Maven is essentially a project management and comprehension tool and as such provides a way to help with managing:

• Builds
• Documentation
• Reporting
• Dependencies
• SCMs
• Releases
• Distribution

If you want more background information on Maven you can check out The Philosophy of Maven and The History of Maven. Now let's move on to how you, the user, can benefit from using Maven

12. Discuss how Maven uses conventions over configurations, explaining Maven’s approach to manage the configurations 

Maven uses Convention over Configuration, which means developers are not required to create build process themselves.

Developers do not have to mention each and every configuration detail. Maven provides sensible default behavior for projects. When a Maven project is created, Maven creates default project structure. Developer is only required to place files accordingly and he/she need not to define any configuration in pom.xml.

13. Discuss the terms build phases, build life cycle, build profile, and build goal in Maven 

       Terms build phases
       A Maven phase represents a stage in the Maven build lifecycle. Each phase is responsible for a specific task.

       Build life cycle
                A Build Lifecycle is a well-defined sequence of phases, which define the order in which the goals are to be executed

       Build profile
                A Build profile is a set of configuration values, which can be used to set or override default values of Maven build.
               When we execute mvn post-clean command, Maven invokes the clean lifecycle consisting of the following phases.
              •pre-clean
              • clean
              •post-clean

       Build goal
Each phase is a sequence of goals, and each goal is responsible for a specific task.

Here are some of the phases and default goals bound to them

• compiler:compile 
• compiler:testCompile 
• surefire:test 
• install:install 
• jar:jar and war:war 

14. Discuss with examples, how Maven manages dependency/packages and build life cycle 

Maven build life cycle

A Build Lifecycle is a sequence of tasks we used to build a software. For example, compile, test, test more, package and publish or deploy are all tasks we need to do to build a software.

A Maven build lifecycle is a sequence of phases we need to go through in order to finishing building the software

Maven manages dependency/packages

Dependency management is a core feature of Maven. Managing dependencies for multi-module projects and applications that consist of hundreds of modules is possible. Maven helps a great deal in defining, creating, and maintaining reproducible builds with well-defined classpaths and library versions.

15. Identify and discuss some other contemporary tools and practices widely used in the software industry 

ADDITIONAL TOOLS AND PRACTICES

   Continuous Integration 
Continuous integration is a software development practice where members of a team integrate their work frequently, usually each person integrates at least daily – leading to multiple integrations per day. Continuous integration software tools can be used to automate the testing and build a document trail.

   Configuration Management 
Configuration Management helps organizations to systematically manage, organize, and control the changes in the documents, codes, and other entities during the Software Development Life Cycle. It aims to control cost and work effort involved in making changes to the software system.
                   

   Test automation 
HPE UFT offers testing automation for functional and regression testing for the software applications. Visual Basic Scripting Edition scripting language is used by this tool to register the test processes and operates the various objects and controls in testing the applications.

   Issue/bug tracking tools 

     

      Most Popular Bug Tracking Software

•         Plutora Test
•         Airbrake
•         Backlog
•         ReQtest
•         Bugzilla
•         JIRA
•         Mantis
•         Trac

             Agile methodologies

        Agile software development is an approach to software development under which requirements and solutions evolve through the collaborative effort of self - organizingand cross-functional teams and their end user. It advocates adaptive planning, evolutionary development, empirical knowledge, and continual improvement, and it encourages rapid and flexible response to change