CEN 4010 Introduction to Software Engineering Instructor Masoud

CEN 4010 Introduction to Software Engineering Instructor: Masoud Sadjadi http: //www. cs. fiu. edu/~sadjadi/Teaching CEN 4010 - Second Lecture

Acknowledgements Overview: Introduction Evaluation Dr. Peter Clarke Dr. Betty Cheng Dr. Bernd Bruegge Dr. Allen Dutoit SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 2

What is Software Engineering? (1) Overview: Introduction Systematic approach for developing software “Methods and techniques to develop and maintain quality software to solve problems. ” [Pfleeger, 1990] “Study of the principles and methodologies for developing and maintaining software systems. ” [Zelkowitz, 1978] “Software engineering is an engineering discipline which is concerned with all aspects of software production. ” [Sommerville] Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 3

What is Software Engineering? (2) Overview: Introduction “Practical application of scientific knowledge in the design and construction of computer programs and the associated documentation required to develop, operate, and maintain them. ” [Boehm, 1976] “Deals with establishment of sound engineering principles and methods in order to economically obtain software that is reliable and works on real machines. ” [Bauer, 1972] Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 4

Questions Addressed by SE Overview: Introduction How do we ensure the quality of the software that we produce? How do we meet growing demand still maintain budget control? How do we avoid disastrous time delays? Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 5

Why apply SE to Systems? Overview: Introduction Provide an understandable process for system development. Develop systems and software that are maintainable and easily changed. Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle Develop robust software and system. Allow the process of creating computingbased systems to be repeatable and manageable. CEN 4010: Introduction to Software Engineering Second Lecture 6

How can we apply SE? Overview: Introduction Modeling Problem-solving Knowledge acquisition Rationale-driven Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 7

Modeling Overview: Introduction “A model is an abstract representation of a system that enables us to answer questions about the system. ” Why use a model? Home Page SE Overview Definition How to apply? Course Outcome – Systems are too large, too small, too complicated, or too expensive, to experience firsthand. Evaluation SW Life Cycle Models allow – Visualization – Comprehension CEN 4010: Introduction to Software Engineering Second Lecture 8

Problem Solving Overview: Introduction Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle Steps in problem solving: – Formulate the problem – Analyze the problem – Search for solutions – Decide on the appropriate solution – Specify the solution CEN 4010: Introduction to Software Engineering Second Lecture 9

Knowledge Acquisition Overview: Introduction Domain specific knowledge. New knowledge can affect the development process. Knowledge acquisition is nonlinear – affects several of the software development models. Risk assessment is important. Home Page SE Overview Definition How to apply? Course Outcome Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 10

Rationale Management Overview: Introduction Assumptions made about systems change constantly. Application domain models stabilize, solution domain models are in constant flux. Home Page SE Overview Definition How to apply? Course Outcome – Changes to the solution models due to: Evaluation SW Life Cycle design and implementation faults new technology Need to understand the context in which each design decision was made. CEN 4010: Introduction to Software Engineering Second Lecture 11

Course Outcomes Overview: Introduction Home Page SE Overview Course Outcome Evaluation SW Life Cycle Familiarity with the Software Development Life Cycle. Mastering the techniques to gather and specify the requirements of a medium-size software system using UML. Mastering the techniques to design and implement a medium-size software system. Familiarity with software testing techniques. Familiarity with software documentation. Familiarity with working in a small software development team. Familiarity with system walkthroughs. Familiarity with maintaining software and managing change. CEN 4010: Introduction to Software Engineering Second Lecture 12

Evaluation Overview: Introduction What is Software Engineering? What questions are answered by Software Engineering? How can we apply Software Engineering? What should you expect from this class? What are the outcomes? Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 13

Agenda Overview: Introduction Course Introduction Evaluation Software Life Cycle Evaluation SW Life Cycle CEN 4010: Introduction to Software Engineering Second Lecture 14

Our Intention Overview: Introduction Evaluation SW Life Cycle Motivation Requirements Terminology SW Processes SW Life Cycle Cap. Maturity Software CEN 4010: Introduction to Software Engineering Second Lecture 15

Our plan of attack Overview: Introduction Evaluation SW Life Cycle Requirements Analysis Motivation Terminology SW Processes Design SW Life Cycle Cap. Maturity Implementation Testing Delivery and Installation CEN 4010: Introduction to Software Engineering Second Lecture 16

How it often goes Overview: Introduction Evaluation SW Life Cycle Requirements Analysis Motivation Terminology SW Processes SW Life Cycle Cap. Maturity D E L A Y CEN 4010: Introduction to Software Engineering Vaporware Second Lecture 17

Inherent Problems Overview: Introduction Requirements are complex – The client does not know the functional requirements in advance. Evaluation SW Life Cycle Motivation – Technology enablers introduce new possibilities to deal with nonfunctional requirements. Terminology SW Processes SW Life Cycle Cap. Maturity Requirements may be changing Frequent changes are difficult to manage – Identifying milestones and cost estimation are difficult. There is more than one software system – Backward compatible with existing systems Let’s view these problems as the nonfunctional requirements for a system that supports software development! – This leads us to software life cycle modeling CEN 4010: Introduction to Software Engineering Second Lecture 18

Terminology (1) Overview: Introduction Evaluation SW Life Cycle e. g. , developers, project manager, client, end users. Motivation Terminology SW Processes SW Life Cycle Cap. Maturity participants – all persons involved in a project. role – associated with a set of tasks assigned to a participant. system – underlying reality. model – abstraction of the reality. work product – an artifact produced during development. deliverable – work product for client. CEN 4010: Introduction to Software Engineering Second Lecture 19

Terminology (2) Overview: Introduction Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Cap. Maturity activity – a set of tasks performed toward a specific purpose. milestone – end-point of a software process activity. task – an atomic unit of work that can be managed and that consumes resources. goal – high-level principle used to guide the project. functional requirement – an area of functionality that the system must have. CEN 4010: Introduction to Software Engineering Second Lecture 20

Terminology (3) Overview: Introduction Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Cap. Maturity nonfunctional requirement – a constraint on the system. notation – is a graphical or textual set of rules representing a model (e. g. , UML) method – a repeatable technique for solving a specific problem e. g. sorting algorithm methodology – a collection of methods for solving a class of problems (e. g. , Unified Software Development Process). CEN 4010: Introduction to Software Engineering Second Lecture 21

Software Processes Overview: Introduction 1. Specification – requirements elicitation and analysis. Evaluation SW Life Cycle Motivation Terminology 2. Development – systems design, detailed design (OO design), implementation. SW Processes SW Life Cycle Cap. Maturity 3. Validation – validating system against requirements (testing). 4. Evolution – meet changing customer needs and error correction (maintenance). CEN 4010: Introduction to Software Engineering Second Lecture 22

1. Software Specification (1) Overview: Introduction Functionality of the software and constraints (non-functional requirements) on its operation must be defined. Involves: Evaluation SW Life Cycle Motivation Terminology SW Processes Specification Development Validation Evolution SW Life Cycle Cap. Maturity – Requirements elicitation – The client and developers define the purpose of the system. – Output is a description of the system in terms of actors and uses cases. – Actors include roles such as end users and other computers the system needs. CEN 4010: Introduction to Software Engineering Second Lecture 23

1. Software Specification (2) Overview: Introduction Evaluation SW Life Cycle Uses cases are general sequences of events that describe all possible actions between actor and the system for a given piece of functionality. Motivation Terminology SW Processes Specification Analysis Development Validation Evolution SW Life Cycle Cap. Maturity Objective: produce a model of the system that is correct, complete, consistent, unambiguous, realistic, and verifiable. Developers transform the use cases into an object model that completely describes the system. Model is checked for ambiguities and inconsistencies. Output: Object model annotated with attributes, operations, and associations. CEN 4010: Introduction to Software Engineering Second Lecture 24

2. Software Development (1) Overview: Introduction Evaluation SW Life Cycle Producing the software that meets the specification. Motivation Terminology SW Processes System Design Specification Development Validation Evolution SW Life Cycle Goals of the project are defined. System decomposed into smaller subsystems (architectural model). Strategies to build system identified – HW and SW platform, data management, control flow, and security. Cap. Maturity Output: model describing subsystem decomposition and system strategies. CEN 4010: Introduction to Software Engineering Second Lecture 25

2. Software Development (2) Overview: Introduction Evaluation Object Design SW Life Cycle Motivation Terminology SW Processes Specification Development Validation Evolution SW Life Cycle Cap. Maturity Bridges the gap between analysis model and the strategies identified in the system design. Includes: – Describing object and subsystem interfaces – Selecting off–the-shelf components – Restructure object model to attain design goals e. g. , extensibility, understandability, and required performance. Output: detailed object model annotated with constraints and supporting documentation. Implementation Translation of the object model into source code. No general process followed. There are tools to assists the programmer such as CASE tools. CEN 4010: Introduction to Software Engineering Second Lecture 26

Software Development Activities Overview: Introduction Evaluation Requirements Analysis What is the problem? System Design What is the solution? SW Life Cycle Motivation Terminology SW Processes Specification Development Validation Evolution SW Life Cycle Object Design What is the solution in a specific context? Implementation How is the solution constructed? Problem Domain Implementation Domain Cap. Maturity CEN 4010: Introduction to Software Engineering Second Lecture 27

3. Software Validation (1) Overview: Introduction Evaluation SW Life Cycle Motivation Terminology Ensures the software does what the customer want. The software conforms to its specification and meets the expectations of the customer. SW Processes Specification Development Validation Evolution SW Life Cycle Cap. Maturity Validation: ‘Are we building the right product? ’ Ensures the software meets the expectations of the customer. Verification: ‘Are we building the product right? ’ Ensures the software conforms to the specification. CEN 4010: Introduction to Software Engineering Second Lecture 28

3. Software Validation (2) Overview: Introduction Techniques – Software inspections (static): Evaluation SW Life Cycle Motivation Terminology Analyze and check system representations (e. g. , requirements documents, design diagrams, and program source code). – Software testing (dynamic): SW Processes Specification Development Validation Executing an implementation of the software with test data and examining the outputs against expected results. Evolution SW Life Cycle Cap. Maturity V&V process establishes the existence of defects. Debugging is a process that locates and corrects these defects. CEN 4010: Introduction to Software Engineering Second Lecture 29

4. Software Evolution Overview: Introduction Evaluation SW Life Cycle Software must evolve to meet the customer needs. Motivation Terminology SW Processes Software maintenance is the process of changing a system after it has been delivered. Reasons for maintenance Specification Development Validation Evolution SW Life Cycle Cap. Maturity – To repair faults. – To adapt the software to a different operating environment. – To add to or modify system’s functionality. CEN 4010: Introduction to Software Engineering Second Lecture 30

Attributes of Good Software Overview: Introduction Maintainability – Ease of changing the software to meets the changing needs of the customer. Evaluation SW Life Cycle Motivation Terminology SW Processes Dependability – Reliability, security and safety. Specification Development Validation Evolution Efficiency – Responsiveness, processing time, and memory usage. SW Life Cycle Cap. Maturity Usability – Appropriate user interface and adequate documentation. CEN 4010: Introduction to Software Engineering Second Lecture 31

Software Life Cycle Overview: Introduction Software life cycle modeling – Attempt to deal with complexity and change. Evaluation SW Life Cycle Motivation Terminology Software life cycle – Set of activities and their relationships to each other to support the development of a software system. SW Processes SW Life Cycle Cap. Maturity Software development methodology – A collection of techniques for building models, which are applied across the software lifecycle. CEN 4010: Introduction to Software Engineering Second Lecture 32

Software Life Cycle Overview: Introduction Evaluation Software construction goes through a progression of states SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Conception Childhood Adulthood Retirement Cap. Maturity Pre. Development CEN 4010: Introduction to Software Engineering Post. Development Second Lecture 33

Software Life Cycle Models Overview: Introduction Waterfall model and its problems – Pure Waterfall Model – V-Model Evaluation SW Life Cycle Motivation Terminology SW Processes Iterative process models – Boehm’s Spiral Model – Unified Process Model SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity Entity-based models – Issue-based Development Model – Concurrent Development CEN 4010: Introduction to Software Engineering Second Lecture 34

Waterfall Model (1) Overview: Introduction – First described by Royce in 1970 Evaluation SW Life Cycle Motivation Terminology The waterfall model There seem to be at least as many versions as there authorities - perhaps more SW Processes SW Life Cycle Requirements Definition Waterfall Iterative System and software design Entity-Based Cap. Maturity Implementation and unit testing Integration and system testing Operation and maintenance CEN 4010: Introduction to Software Engineering Second Lecture 35

Waterfall Model (2) Overview: Introduction One or more documents are produced after each phase and “signed off”. Points to note: Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity – “Water does not flow up”. it is difficult to change artifact produced in the previous phase. – This model should be used only when the requirements are well understood. – Reflects engineering practice. – Simple management model. CEN 4010: Introduction to Software Engineering Second Lecture 36

From Waterfall to V Model Overview: Introduction Evaluation Horizontal lines denote the information flow between activities at the same abstraction level. SW Life Cycle Motivation Terminology Requirements Specification Acceptance test SW Processes SW Life Cycle Waterfall System and integration test System design Iterative Entity-Based Cap. Maturity Detailed Design Unit Test Implementation CEN 4010: Introduction to Software Engineering Second Lecture 37

V Model Overview: Introduction Similar to pure waterfall model but makes explicit the dependency between development and verification activities. The left half of the V represents development and the right half system validation. Note the requirements specification includes requirements elicitation and analysis. Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity CEN 4010: Introduction to Software Engineering Second Lecture 38

Spiral Model (1) Overview: Introduction Basic Idea – develop initial implementation, expose it to user, and refine it until an adequate system is produced. Evaluation SW Life Cycle Motivation Terminology SW Processes Two types: – Exploratory – Throw-away prototyping SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity Advantages – model used when problem is not clearly defined. Disadvantages – Process not visible, systems are poorly constructed, may require special tools and techniques. CEN 4010: Introduction to Software Engineering Second Lecture 39

Spiral Model (2) Overview: Introduction Design objectives, alternatives, and constraints Evaluate alternatives, identify and resolve risks Evaluation Risk analysis SW Life Cycle Risk analysis Motivation Terminology Risk analysis SW Processes Prototype 3 Prototype 2 1 SW Life Cycle Waterfall Requirements Concept of plan operation S/w Reqs. Iterative Entity-Based Development Plan Cap. Maturity Integration Plan Design Validation Acceptance Test Plan next phase CEN 4010: Introduction to Software Engineering Detailed Design Sys. Product Design Reqs. Validation Not shown in detail Code Unit Test Integration & Test Develop and verify next level product Second Lecture 40

Spiral Model (3) Overview: Introduction Tries to accommodate infrequent change during development. Each round of the spiral involves: Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity – – – – Determine objectives Specify constraints Generate alternatives Identify risks Resolve risks Develop and verify next level product Plan CEN 4010: Introduction to Software Engineering Second Lecture 41

Incremental Development (1) Overview: Introduction Mills et al. 1980 Evaluation SW Life Cycle Motivation Terminology SW Processes Define outline requirements Assign requirements to increments Design system architecture SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity Develop system increment Validate increment Integrate increment Validate system Final system System incomplete CEN 4010: Introduction to Software Engineering Second Lecture 42

Incremental Development (2) Overview: Introduction Software specification, design and implementation is broken down into a series of increments which are developed in turn. Gives customers some opportunities to delay decisions on the detailed requirements of the system. Services are identified and a priority allocated. Each increment provides a subset of the system’s functionality. Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity CEN 4010: Introduction to Software Engineering Second Lecture 43

Incremental Development (3) Overview: Introduction Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Advantages: – Customers do not have to wait for the entire system. – Customers gain experience using early increments of the system. – Lowers the risk of overall project failure. – Most important system services receives the most testing. Iterative Entity-Based Cap. Maturity Disadvantages: – May be difficult to map meaningful functionality into small increments. CEN 4010: Introduction to Software Engineering Second Lecture 44

Extreme Programming Overview: Introduction The incremental approach has evolved to ‘extreme programming’ (Beck 1988). Extreme programming: Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Iterative Entity-Based Cap. Maturity – – Development and delivery of very small increments. Customer involvement in the process. Constant code improvement. Egoless programming Programs are regarded as group property! CEN 4010: Introduction to Software Engineering Second Lecture 45

Unified Software Development Process (1) Overview: Introduction Similar to Boehm’s spiral model. A project consists of several cycles, each ends with the delivery of a product to the customer. Each cycle consists of four phases: Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall Iterative – – Entity-Based Cap. Maturity Inception Elaboration Construction Transition Each phase consists of a number of iterations. CEN 4010: Introduction to Software Engineering Second Lecture 46

Unified Software Development Process (2) Overview: Introduction Inception ends with – commitment from the project sponsor to go ahead. Evaluation SW Life Cycle Motivation Terminology Elaboration ends with – – SW Processes SW Life Cycle Waterfall Iterative basic architecture of the system in place, a plan for construction agreed, all significant risks identified, and major risks understood enough not to be too worried. Entity-Based Cap. Maturity Construction ends with – a beta-release system. Transition – is the process of introducing the system to it users. CEN 4010: Introduction to Software Engineering Second Lecture 47

Unified Software Development Process (2) Overview: System Development Introduction Evaluation SW Life Cycle specified by Motivation Analysis model Terminology realized by SW Processes Design model SW Life Cycle Waterfall Iterative Use case model Entity-Based distributed by Deployment model implemented by Cap. Maturity Requirements captured as a set of use cases. verified by Implementation model Test model CEN 4010: Introduction to Software Engineering Second Lecture 48

Unified Software Development Process (3) Overview: Introduction – physical communication links between hardware items. Evaluation SW Life Cycle Motivation – relationships between physical machines and processes. Terminology SW Processes SW Life Cycle Deployment model Waterfall Iterative The models in the Unified Process are traceable – A model element can be traced to at least one element in an associated model. Entity-Based Cap. Maturity Transition between models are seamless – we can tell in a foreseeable way how to get from an element in one model to one/more elements in an associated model. CEN 4010: Introduction to Software Engineering Second Lecture 49

Issue-Based Development Overview: Introduction A system is described as a collection of issues – Issues are either closed or open. – Closed issues have a resolution. – Closed issues can be reopened (Iteration!). Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Waterfall The set of closed issues is the basis of the system model Iterative Entity-Based I 1: Open Cap. Maturity A. I 1: Open SD. I 1: Closed SD. I 3: Closed I 2: Closed I 3: Closed Planning A. I 2: Open Requirements Analysis CEN 4010: Introduction to Software Engineering SD. I 2: Closed System Design Second Lecture 50

What to Choose? Overview: Introduction PT = Project Time, MTBC = Mean Time Between Change rarely occurs (MTBC >> PT): Evaluation SW Life Cycle – Waterfall Model – All issues in one phase are closed before proceeding to the next phase Motivation Terminology SW Processes SW Life Cycle Change occurs sometimes (MTBC = PT): – Boehm’s Spiral Model – Change occurring during a phase might lead to an iteration of a previous phase or cancellation of the project Cap. Maturity “Change is constant” (MTBC << PT) – Issue-based Development (Concurrent Development Model) – Phases are never finished, they all run in parallel Decision when to close an issue is up to management. The set of closed issues form the basis for the system to be developed. CEN 4010: Introduction to Software Engineering Second Lecture 51

Capability Maturity Model (CMM) Overview: Introduction Evaluation SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Cap. Maturity 1. Initial Level – ad hoc, no feedback from user, black box. 2. Repeatable Level – Each project has a well-defined sw life cycle model. 3. Defined Level – A document sw life cycle model for all managerial and technical activities across the org. exists. 4. Managed Level – Metrics for activities and deliverables are defined. 5. Optimizing Level – Process allows feedback of information to change process itself. CEN 4010: Introduction to Software Engineering Second Lecture 52

State of the Software Industry in 1995 Overview: Introduction Evaluation Maturity Level Frequency SW Life Cycle Motivation Terminology SW Processes SW Life Cycle Cap. Maturity 1. Initial 2. Repeatable 3. Defined 4. Managed 5. Optimizing 70% 15% < 10% < 5% < 1% Source: Royce, Project Management, P. 364 CEN 4010: Introduction to Software Engineering Second Lecture 53