SE Process Steps and Requirements Allocation

EMIS 7307 Problem definition Consumer need Feasibility System operational requirements Maintenance and support concepts Determine/prioritize TPMs Functional analysis Requirements allocation System synthesis Design integration T&E Production Operational use Retirement Chapter 3 From Chapter 2 we had these “steps” in the SE process:

EMIS 7307 Chapter 3 From SE Fundamentals

EMIS 7307 Chapter 3 • Notice how the steps on previous slide map into Fig 3.1 and Fig 1.12. • In Fig 3.2 the MIL-STD-490 terms are used. • Type A, B etc. • Names aren’t important the ideas of flowdown and increasing design detail are! • We’ll use the “490” terminology but understand the meaning behind the type.

EMIS 7307 Chapter 3 • Type A (system spec) - usually only 1. • Technical, performance, operational and support characteristics of the system as whole. • Feasibility,operational requirements, functional analysis products go here. • Defines subsystems. • Has a Section 4!

EMIS 7307 Chapter 3 • Type B (development spec) - usually several. • Technical, performance, operational and support characteristics of specific subsystems. • Performance, effectiveness, and support characteristics are included. • Defines assemblies or CSCIs. • Has a Section 4!

EMIS 7307 Chapter 3 • Type C (product spec) - usually many. • Design details. • Hardware separate from software. • Has a Section 4! • Type D and E • Specific process and material requirements.

EMIS 7307 Chapter 3 • The requirement allocation process selects assignments of specific allocated requirements to specific specifications. • See Fig 3.3 for an example of a spec “tree”. • Order of precedence is important!

EMIS 7307 Chapter 3 • See Fig 3.4. • Type A, • TPMs usually here. • These are the typically used sections. • The essence is the important part but, using this format is comfortable within DOD. • Types B, C etc are typically laid-out the same. • Next page from SEF Guide.

EMIS 7307 software development reliability maintainability human factors safety security producibility logistics disposability quality environmental value/cost Chapter 3 Blanchard selects 12 design disciplines for further discussion because they have been historically inadequately integrated into system developments and mainstream design effort. They are: We’ll discuss them briefly, be sure to be aware of the existence of them all and the type of engineering they accomplish!

EMIS 7307 Chapter 3 • Software engineering things to know: • Same processes and flow in the system engineering of software as hardware. • Software engineers may have their own special names but they are equivalent. • Testing subroutines, subprograms and integration into programs flows in a similar fashion as hardware.

EMIS 7307 Chapter 3 • Software engineering things to know: • Verification can include evaluating the consequences of every data path regardless of it’s use likelihood. • Stress testing explores the limits of i/o, throughput and processing. • Software QC deals with subjects like - were the standards followed? • Following three charts are examples of software development methodologies...

EMIS 7307 Structured Analysis, Structured Design User Requirements Analysis User Requirements Specifications Software Requirements Specification System/Broad Design Logical Design Program/Detailed Design Physical Design Implementation/Coding Program Testing: Units Program Testing: System Program Use Software Maintenance

EMIS 7307 Requirements Analysis Design 1 Implement 1 Design 2 Implement 2 Design 3 Implement 3 Test Planning Certification 1 Certification 2 Certification 3

EMIS 7307 Effort Implementation Detailed Design Broad Design Software requirements Requirements analysis Time Object Oriented Design Basic Classes Specific Classes I disagree with the author’s note 12 page 127. Objects are determined by the functional flowdown.

EMIS 7307 Chapter 3 • Reliability Engineering things to know: • Probability based. • Item is considered reliable if the mission of the device is accomplished. • Implies a component may fail it’s mission while the system may not fail it’s mission and vice versa • R, MTBF and  are important parameters. • R= e-t where t = operating time and = average failure rate. • e-t represents the probability of zero failures in t.

EMIS 7307 Chapter 3 • Reliability Engineering things to know: • Look at the typical failure curves in Fig 3.8. • What’s the difference between a software failure and a hardware failure? • Note the effects of redundancy on reliability in Fig 3.11. • In Fig 3.14 items 1-5 are for SE’s, and 17-20 for testers (also SE’s).

EMIS 7307 Chapter 3 • Reliability Engineering things to know: • Importance of FRACAS! • Suggest an automated problem identification and notification system! • Anyone who suspects a problem documents it and then it gets dispositioned (i.e. reviewed and actions assigned to correct as required). • Let’s look at the reliability qualification testing paragraph page 142, para7 • Notice the synergism that can/should occur • Results in time and $ savings

EMIS 7307 Chapter 3 • Maintainability Engineering things to know: • Maintainability is the ability of an item to be maintained. • Maintenance is the action to restore or retain a specified operating condition. • See the time relationships in Fig 3.17. • A log-normal distribution is typical of maintenance times. See Fig 3.18.

EMIS 7307 Chapter 3 • Maintainability Engineering things to know: • See Fig 3.19. How many were false alarms? • Availability is the factor of interest to your customer. • A = MTBM/(MTBM + MDT) • If one has or anticipates low A what’s the fix? • Lots of units, Lots of spares, Lots of maintenance personnel, Lots of $$$$! • Maintainability demonstrations are valuable but extremely expensive (See page 156) • Look for alternative ways to get the data.

EMIS 7307 Chapter 3 • Human factors engineering things to know: • Human as a part of the system! • Called ergonomics, considers: • Size (page 159). • Senses. • Physiological factors. • Psychological factors. • Interface called MMI. • This interface requires as much or more definition as machine to machine. This can be a big time consumer.

EMIS 7307 Chapter 3 • Human factors engineering things to know: • Mockups and simulators likely required during design. • Human subjects typical of end user (I.Q., training, etc.) needed as test subjects during design. • See Fig 3.26 for tasks especially #15- testing.

EMIS 7307 Chapter 3 • Safety engineering things to know: • This is not about conducting a test safely. • This is about designing a system to minimize human and hardware/software exposure to unsafe conditions. • When a hazard can’t be eliminated then safety engineering determines a safe (acceptable risk) way to deal with it.

EMIS 7307 Chapter 3 • Safety engineering things to know: • Notice how many of the “ilities” come together synergistically (integrated by the SEMP) to support safety. • Paragraph 1 section 3.4.5 page 167.

EMIS 7307 Chapter 3 • Security engineering things to know: • Prevents planned introduction of faults/failures. • Similar to preventing inadvertent faults by careless operators… except for intent. • Includes encryption techniques and devices. • Virus detectors and physical access barriers are examples.

EMIS 7307 critical materials critical processes proprietary items special production tooling unrealistic tolerances special test systems highly skilled personnel production/procurement lead times Chapter 3 • Producibility engineering things to know: • Objective is to convert the results of R&D efforts into something that can be produced outside the lab. • Minimize the following:

EMIS 7307 Chapter 3 • Logistics engineering things to know: • Figure 3.32 is a good summary of the elements of logistics. • Figure 3.33 shows when engineering can influence the design to reduce risk and costs. • Logistics is an area with tremendous lifetime costs ! • OT&E is the typical place for evaluation of the logistics “stream”.

EMIS 7307 Chapter 3 • Quality engineering things to know: • QC and QA are after the fact i.e. checking the final product. • TQM and QFD are from the beginning. • Emphasis on the following: • Customer satisfaction – no satisfaction – no quality. • Continuous improvement. • Variability minimization (6 sigma). • Everyone (not just an inspector) involved.

EMIS 7307 Chapter 3 • Environmental engineering things to know: • Ecological, political and social factors. • Affects test choices e.g.: • Bombing range in Puerto Rico. • Sonar test impact on whales. • Use and retirement issues. • Lithium batteries in airplanes. • Nuclear “leftovers” like old submarine reactors -where do you dispose of them?

EMIS 7307 Chapter 3 • Value/Cost engineering things to know: • See top of page 188 for examples of “figures of merit”. • From a functional flow diagram, estimate the costs of the various functions from beginning to end. • Lots of models exist. • Appendix B provides details and examples. • LCC analysis may justify expensive testing.

SE Process Steps and Requirements Allocation