Chapter 1. Software and Software Engineering. What is this course about?

Transcription

1 Chapter 1 Software and Software Engineering 1 What is this course about? 2

2 SW Development Project > > SW Eng Process > SW Product Analysis + Design models: DFDs, ERDs, STDs, DOs, etc. Coding, programming, code testing, validation, verificationetc. SW PROJECT PROCESS = Software Engineering PRODUCT: SW App Customer and his/her project FTR # 1 FTR # 2 FTR # 3 Final Software product Analysis: requirements (scope, functionality, constraints, user scenarios, data flow, patterns, Web apps, etc.) (ch. 4-7) Baseline Project Plan Design: concepts, models, system s architecture, system s components, graphic user interface (GUI), prototyping, etc. (ch. 8-13) Software Quality: concepts, techniques, testing, metrics (ch ) SW Dev. Project Management: concepts, metrics, estimates, scheduling, risk m., configuration m., etc. (ch ) 3 Software Product (SW) 4

3 What is Software (SW)? Software (SW) is: 1) Instructions 2) Data structures 3) Documents (computer programs) that when executed provide desired function and performance; (files structures) that enable the programs to adequately manipulate stored information, and that describe the operation and use of the programs. SW is used to perform the following functions: 1) produce, 2) manage, 3) acquire, 4) modify, 5) display, and 6) transmit information anywhere in the world. SW is a product designed and developed by software engineers. Software Engineering is a process,, a set of methods, and an array of tools to design and build top quality SW. 5 What is Software? SW is engineered (developed); it is not manufactured or assembled in the classical sense. Opportunities for SW replication without customization are NOT very common in SE. *) Cars (GM components for all Pontiac, GM, Chevy, etc. cars) *) SW (Word for Linux???; VB 2008 for Mac???) SW may become deteriorated (old, obsolete); but SW doesn t wear out. *) SW that uses COBOL programs years old. The main reason for SW to deteriorate is that many changes are made to a SW product over its lifetime due to new desired functions and features. *) Windows 3.1, 3.11, 95, 98, 2000, XP, 2003, Visat,, 7, etc. *) Event-driven programming: VB4, VB6, VB.Net,, VB2005, VB2008 6

4 Wear vs. Deterioration Failure rate increased failure rate due to side effects change actual curve idealized curve Time 7 What is Software? SW is complex (sometime VERY complex) product *) 1968 APOLLO program (1million lines of code in FORTRAN) 1 mistake $ 1.2 million *) 1994 Pentium II 1 mistake - $467 million (Intel) *) Windows Vista OS??? Although SW development industry is moving toward SW component- based construction: *) GUI: reusable graphic elements (menus, objects, etc. in GUI of o MS applications) *) object-oriented oriented programming *) components-based programming However, vast majority of SW systems continue to be custom-built. 8

5 The Cost of SW Change X x 1X 1x 1.5 6XX 1.5-6x Analysis Definition Design, Development Coding, After release SW system Testing release 9 Various Types of Software Applications General purpose software : * System SW (operating systems) Specific purpose (problem-oriented) oriented) software: 1) Business SW (IS, MIS, KWS, ES, DSS, etc.) 2) Engineering/scientific SW (industrial apps, calculations, simulation, CAD, CAE, CAM) 3) PC (PDA) SW (PC- and PDA-oriented oriented SW) 4) Real-time SW (monitors events in real time: military, security apps) 5) Embedded SW (with limited number of functions and weak functionality; microprocessors in consumer electronics). 6) AI SW (uses non-numerical numerical algorithms to solve problems; for example, IF-THEN THEN-ELSE ELSE production rules; predictions, prognosis apps) 7) Web Applications (HTML, Java instructions + hyperlinked data (hypertext) 10

6 In-Class Exercise 11 SW Crisis? The biggest problem facing by modern SW engineers is trying 1) to figure out how to produce SW fast enough AND 2) to meet the growing demand for many different SW products AND 3) to maintain a growing volume of existing SW products (applications) and new software development projects. It is necessary to understand: (by managers): only buying hardware and adding people DOES NOT spontaneously solve all SW development problems (by customers) computer SW solves one problem but it does not make all their other problems go away; if customer cannot define his or her problems or needs clearly, then it is impossible to build a SW to meet these needs. 12

7 Unique Attributes of WebApps (1) 1. Network intensiveness. A WebApp resides on a network and must serve the needs of a diverse community of clients. *) various backgrounds, various computers, various cultures, various 2. Concurrency. A large number of users may access the WebApp at one time; patterns of usage among end-users will vary greatly. *) professionals and kids, young and aged people 3. Unpredictable load. The number of users of the WebApp may vary by orders of magnitude from day to day. *) 10 users or 10,000 users leads to various servers, broadband requirements, and servers If a WebApp user must wait too long (for access, for server-side side processing, for client-side formatting and display), he or she may decide to go elsewhere. 4. Performance. If a WebApp user must wait too long (for access, *) text-based, graphic-based, animation-based, streaming video-based 13 Unique Attributes of WebApps (2) 5. Availability. Users of popular WebApps often demand access on a 24/7/365 basis. *) airlines, hotels, etc. Maintenance and updates/upgrades is an issue 6. Content sensitive. The quality and aesthetic nature of content remains an important determinant of the quality of a WebApp. *) especially, for educational and governmental web sites 7. Data driven. The primary function of many WebApps is to use hypermedia to present text, graphics, audio, and video content to the end-user (to make Web content more comfortable and convenient for users) *) especially, for educational web sites (see example below) 8. Continuous evolution. Unlike conventional application software that evolves over a series of planned, chronologicallyspaced releases, Web applications evolve continuously. *) especially, for educational web sites (see example below) 14

8 Dr. Uskov s Evolution of e-learning e Courseware Continuous Evolution Learners can HEAR, SEE, SAY WRITE and DO ( RF: 65%-95%) Learners can HEAR and SEE ( RF: 40%-70%) Learners can SEE ( RF: 40%-50%) Learners can READ (e-learning by e-reading: 20-40% retention factor) 15 Bradley University: Streaming Technology (Video, Audio, Data) + Simulations at Bradley University Video/ Audio Text PPT slides Pictures Bulletin B. Chat Whiteboard Video-conf. Audio-conf. Data-driven App. + Availability (24/7) Web-based Animation Web-based programming and simulation 16

9 Main Components of a Virtual School System 17 Unique Attributes of WebApps (3) 9. Immediacy. WebApps WebApps often exhibit a time to market that can be a matter of a few days or weeks. With modern tools, sophisticated Web pages can be produced in only a few hours. *) auctions, online tests, etc. 10. Aesthetics. When an application has been designed to market or sell products or ideas, aesthetics may have as much to do with success as technical design. *) online shops (Bad design I will not buy anything here) 11. Security. In order to protect sensitive content and provide secure modes of data transmission, strong security measures must be implemented throughout the infrastructure that supports a WebApp and within the application itself. *) military apps, patients medical records, etc. 18

10 Aug 27, 2012, 10:47 AM ation.aspx 19 Software Engineering The IEEE definition: Software Engineering: The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software. 20

11 SE: A Layered Technology Software Engineering Tools Methods Process Model Goal = produce top quality product 1) SE rests on a goal - an organizational commitment to produce top quality product. 2) Process layer (that uses formal process models) is the glue that holds the SE technology layers together. 3) Methods to provide the concrete technical HOW-TO s for building SW. 4) Tools to provide automated or semi-automated support for SW development. 21 Software Development: Core Activities (SWLC) Initiation (communication) Planning Modeling/Simulation/Prototyping Analysis of requirements Design Model Development (construction) Code generation Testing Deployment/Implementation Communication / Initiation requirements) Planning / Scheduling Modeling/ Simulation/ Prototyping Construction/Code Development Deployment/Implementation (collaboration with a customer, gathering of requirements, meetings with stakeholders, formulation of doable tasks and (establishes engineering work plan, describes technical risks, lists resource requirements, work products produced, and defines timetable of all project activities) (creation of models to help developers and customers understand the requirements and software design) (code development and testing) (software delivered for customer implementation, evaluation, and feedback) 22

12 SW: Umbrella (Support) Activities Software project management (PM) Formal technical reviews (FTR) Risk management (RM) Software quality assurance (SQA) Measurement Software configuration management (SCM) Reusability management Work product preparation and production Software project management (allows team to assess progress and take corrective action to maintain schedule) Formal technical reviews (assess engineering work products to uncover and remove errors before they propagate to next activity) Risk management (assess risks that may affect project outcomes or quality) Software quality assurance (activities required to maintain software quality) Measurement (define and collect process, project, and product measures to assist the software team in delivering software meeting customer needs) Software configuration management / change management (manage effects of change) Reusability management (defines criteria for work product reuse and establish mechanisms to achieve component reuse) Work product preparation and production (activities to create models, documents, logs, forms, lists, etc.) 23 The Essence of Practice Polya (in 1945) suggests: Software Engineering/Development: 1. Understand the problem 1. communication and analysis 2. Plan a solution 2. modeling and software design 3. Carry out the plan 3. code generation 4. Examine the result for accuracy 4. testing and quality assurance (see details below) 24

13 Step # 1: Understand the Problem Who has a stake in the solution to the problem? That is, who are the stakeholders? What are the unknowns? What data, functions, and features are required to properly solve the problem? Can the problem be compartmentalized? Is it possible to represent smaller problems that may be easier to understand? Can the problem be represented graphically? Can an analysis model be created? 25 Step # 2: Plan the Solution Have you seen similar problems before? Are there patterns that are recognizable in a potential solution? Is there existing software that implements the functions, and features that are required? Has a similar problem been solved? If so, are elements of the solution reusable? Can subproblems be defined? If so, are solutions readily apparent for the subproblems? Can you represent a solution in a manner that leads to effective implementation? Can a design model be created? data, 26

14 Step # 3: Carry Out the Plan Does the solution conform to the plan? Is source code traceable to the design model? Is each component part of the solution provably correct? Has the design and code been reviewed, or better, have correctness proofs been applied to algorithm? 27 Step # 4: Examine the Result Is it possible to test each component part of the solution? Has a reasonable testing strategy been implemented? Does the solution produce results that conform to the data, functions, and features that are required? Has the software been validated against all stakeholder requirements? 28

15 Software Traditional Challenges How do we ensure the quality of the software that we produce? How do we meet growing demand and still maintain budget control? How do we upgrade an aging "software plant?" How do we avoid disastrous time delays? How do we successfully institute new software technologies? 29 New Software Challenges Ubiquitous computing Creating software to allow machines of all sizes to communicate with each other across networks anywhere in the world Netsourcing Architecting simple and sophisticated net-based applications that benefit targeted end-user markets worldwide Open Source Distributing source code for computing applications so customers can make local modifications easily and reliably make local modifications easily and reliably New economy Building applications that facilitate mass communication and mass product distribution using evolving concepts 30

16 Homework # 1 (for Topic # 1) the outcomes to instructor before NOON of the day of next class. 31