Notes

Outline

Object-Oriented and Classical Software Engineering   Fifth Edition, WCB/McGraw-Hill, 2002 Stephen R. Schach srs@vuse.vanderbilt.edu

CHAPTER 2

Overview Client, Developer, and User Requirements Phase Specification Phase Design Phase Implementation Phase Integration Phase Maintenance Phase Retirement Problems with Software Production: Essence and Accidents Improving the Software Process

The Software Process The life-cycle model CASE tools The individuals

Terminology Systems analysis Requirements + specifications phases Operations mode Maintenance Design Architectural design, detailed design Client, developer, user Internal software development/contract software

Testing Phase? There is NO testing phase Testing is an activity performed throughout software production Verification Performed at the end of each phase Validation Performed before delivering the product to the client

Documentation Phase? There is NO documentation phase Every phase must be fully documented before starting the next phase Postponed documentation may never be completed The responsible individual may leave The product is constantly changing—we need the documentation to do this The design (for example) will be modified during development, but the original designers may not be available to document it

Requirements Phase Assumption The software being considered is economically justifiable Concept exploration Determine what the client needs, not what the client wants Moving target problem

Requirements Phase Testing Rapid prototyping

Requirements Phase Documentation Rapid prototype, or Requirements document

Specification Phase Specifications document (“specifications”) Legal document Must not have phrases like “optimal,” or   “98% complete”

Specification Phase (contd) Specifications must not be Ambiguous Incomplete Contradictory

Specification Phase (contd) Once the specifications have been signed off The software product management plan (SPMP) is  drawn up This is the earliest possible time for the SPMP

Specification Phase Testing Traceability Review Check the SPMP

Specification Phase Documentation Specification document (specifications) SPMP

Design Phase Specification—what Design—how Retain design decisions When a dead-end is reached For the maintenance team Ideally, the design should be open-ended Architectural design Decompose the product into modules Detailed design Design each module: data structures, algorithms

Design Phase Testing Traceability Review

Design Phase Documentation Design Architectural design Detailed design

Implementation Phase Implement the detailed design in code

Implementation Phase Testing Review Test cases Informal testing (desk checking) Formal testing (SQA)

Implementation Phase Documentation Source code Test cases (with expected output)

Integration Phase Combine the modules and check the product as a whole

Integration Phase Testing Product testing Acceptance testing

Integration Phase Documentation Commented source code Test cases for the product as a whole

COTS Software “Shrink-wrapped software” Commercial off-the-shelf (COTS) Nowadays, COTS software is often downloaded “Click-wrapped software” Alpha testing Beta testing

Maintenance Phase Maintenance Any change once the client has accepted the software The most money is devoted to this phase The problem of lack of documentation

Maintenance Phase Testing Regression testing

Maintenance Phase Documentation Record of all changes made, with reasons Regression test cases

Retirement Good software is maintained Sometimes software is rewritten from scratch Software is now unmaintainable because A drastic change in design has occurred The product must be implemented on a totally new hardware/operating system Documentation is missing or inaccurate Hardware is to be changed—it may be cheaper to rewrite the software from scratch than to modify it True retirement is a rare event

Process-Specific Difficulties Does the product meets the user’s real needs? Is the specification document free of ambiguities, contradictions, and omissions?

Inherent Problems of Software Production Hardware has inherent limits So does software No Silver Bullet Complexity Conformity Changeability Invisibility Aristotelian categories Essence Accidents

Complexity Software is far more complex than hardware Traditional abstraction will not work We cannot understand the whole, so we cannot understand any part Management is difficult Maintenance is a nightmare (documentation, too)

Conformity Type 1: Existing gold refinery Type 2: New gold refinery

Changeability Software is easier to change than hardware Pressure to change Reality Useful software Easier to change Software has a long lifetime (~15 yrs)    compared to hardware (~4 yrs)

Invisibility Software is invisible and unvisualizable Complete views are incomprehensible Partial views are misleading However, all views can be helpful

Is There a Silver Bullet? What about High-level languages Time sharing CASE tools These did not solve the intrinsic problems We have experienced 6% annual productivity increase But, no “silver bullet” (order-of-magnitude increase) is possible

Improving the Software Process U.S. Department of Defense initiative Software Engineering Institute (SEI) The fundamental problem with software The software process is badly managed

Improving the Software Process (contd) Software process improvement initiatives Capability maturity model (CMM) ISO 9000-series ISO/IEC 15504

Capability Maturity Model Not a life-cycle model Set of strategies for improving the software process SW–CMM for software P–CMM for human resources (“people”) SE–CMM for systems engineering IPD–CMM for integrated product development SA–for software acquisition These strategies are being unified into CMMI (capability maturity model integration)

SW–CMM A strategy for improving the software process Put forward in 1986 by the SEI Fundamental idea: Improving the software process leads to Improved software quality Delivery on time, within budget Improved management leads to Improved techniques Five levels of “maturity” are defined Organization advances stepwise from level to level

Level 1.  Initial Level Ad hoc approach Entire process is unpredictable Management consists of responses to crises Most organizations world-wide are at level 1

Level 2.  Repeatable Level Basic software management Management decisions should be made on the basis of previous experience with similar products Measurements (“metrics”) are made These can be used for making cost and duration predictions in the next project Problems are identified, immediate corrective action is taken

Level 3.  Defined Level The software process is fully documented Managerial and technical aspects are clearly defined Continual efforts are made to improve quality, productivity Reviews are performed to improve software quality CASE tools are applicable now (and not at levels 1 or 2)

Level 4.  Managed Level Quality and productivity goals are set for each  project Quality, productivity are continually monitored Statistical quality controls are in place

Level 5.  Optimizing Level Continuous process improvement Statistical quality and process controls Feedback of knowledge from each project to the next

Summary

Key Process Areas There are key process areas (KPAs) for each level Level 2 KPAs include: Requirements management Project planning Project tracking Configuration management Quality assurance Compare Level 2: Detection and correction of faults Level 5: Prevention of faults

Experience It takes: 3 to 5 years to get from level 1 to level 2 1.5 to 3 years from level 2 to level 3 SEI questionnaires highlight shortcomings, suggest ways to improve the process Original idea: Defense contracts would be awarded only to capable firms

Experience (contd) Profitability Hughes Aircraft (Fullerton, CA) spent $500K (1987–90) Savings: $2M per year, moving from level 2 to level 3 Raytheon moved from level 1 in 1988 to level 3 in 1993 Productivity doubled Return of $7.70 per dollar invested in process improvement

Other SPI Initiatives Other software process improvement (SPI) initiatives: ISO 9000-series ISO/IEC 15504

ISO 9000 Set of five standards for industrial activities ISO 9001 for quality systems ISO 9000-3, guidelines to apply ISO 9001 to software There is an overlap with CMM, but they are not identical Not process improvement Stress on documenting the process Emphasis on measurement and metrics ISO 9000 is required to do business with the E.U. Also by many U.S. businesses, for example, GE More and more U.S. businesses are ISO 9000 certified

ISO/IEC 15504 Original name: Software Process Improvement Capability dEtermination (SPICE) International process improvement initiative Started by British Ministry of Defence (MOD) Includes process improvement, software procurement Extends and improves CMM, ISO 9000 Framework, not a method CMM, ISO 9000 conform to this framework Now referred to as ISO/IEC 15504 Or just 15504 for short

Process Improvement Data SEI report on 13 organizations in the original study They used a variety of process improvement techniques, not just SW–CMM

Process Improvement Data (contd) Results of 34 Motorola projects