Home > Articles > Programming

The Third Principle of the Incremental Commitment Spiral Model: Concurrent Multidiscipline Engineering

This chapter from The Incremental Commitment Spiral Model: Principles and Practices for Successful Systems and Software discusses the third principle of the model: concurrent multidiscipline engineering.
This chapter is from the book
  • “Do everything in parallel, with frequent synchronizations.”
  • —Michael Cusumano and Richard Selby, Microsoft Secrets, 1995
  • “As the correct solution of any problem depends primarily on a true understanding of what the problem really is, and wherein lies its difficulty, we may profitably pause upon the threshold of our subject to consider first, in a more general way, its real nature: the causes which impede sound practice; the conditions on which success or failure depends; the directions in which error is most to be feared. Thus we shall attain that great perspective for success in any work—a clear mental perspective, saving us from confusing the obvious with the important, and the obscure and remote with the unimportant.”
  • —Arthur M. Wellington, The Economic Theory of the Location of Railroads, 1887

The first flowering of systems engineering as a formal discipline focused on the engineering of complex physical systems such as ships, aircraft, transportation systems, and logistics systems. The physical behavior of the systems could be well analyzed by mathematical techniques, with passengers treated along with baggage and merchandise as a class of logistical objects with average sizes, weights, and quantities. Such mathematical models were very good in analyzing the physical performance tradeoffs of complex system alternatives. They also served as the basis for the development of elegant mathematical theories of systems engineering.

The physical systems were generally stable, and were expected to have long useful lifetimes. Major fixes or recalls of fielded systems were very expensive, so it was worth investing significant up-front effort in getting their requirements to be complete, consistent, traceable, and testable, particularly if the development was to be contracted out to a choice of competing suppliers. It was important not to overly constrain the solution space, so the requirements were not to include design choices, and the design could not begin until the requirements were fully specified.

Various sequential process models were developed to support this approach, such as the diagonal waterfall model, the V-model (a waterfall with a bend upward in the middle), and the two-leg model (an inverted V-model). These were effective in developing numerous complex physical systems, and were codified into government and standards-body process standards. The manufacturing process of assembling physical components into subassemblies, assemblies, subsystems, and system products was reflected in functional-hierarchy design standards, integration and test standards, and work breakdown structure standards as the way to organize and manage the system definition and development.

The fundamental assumptions underlying this set of sequential processes, prespecified requirements, and functional-hierarchy product models began to be seriously undermined in the 1970s and 1980s. The increasing pace of change in technology, competition, organizations, and life in general made assumptions about stable, prespecifiable requirements unrealistic. The existence of cost-effective, competitive, incompatible commercial products or other reusable non-developmental items (NDIs) made it necessary to evaluate and often commit to solution components before finalizing the requirements (the consequences of not doing this will be seen in the failure case study in Chapter 4). The emergence of freely available graphic user interface (GUI) generators made rapid user interface prototyping feasible, but also made the prespecification of user interface requirement details unrealistic. The difficulty of adapting to rapid change with brittle, optimized, point-solution architectures generally made optimized first-article design to fixed requirements unrealistic.

As shown in the “hump diagram” of Figure 0-5 in the Introduction, the ICSM emphasizes the principle of concurrent rather than sequential work for understanding needs; envisioning opportunities; system scoping; system objectives and requirements determination; architecting and designing of the system and its hardware, software, and human elements; life-cycle planning; and development of feasibility evidence. Of course, the humps in Figure 0-5 are not a one-size-fits-all representation of every project’s effort distribution. In practice, the evidence- and risk-based decision criteria discussed in Figures 0-7 and 0-8 in the Introduction can determine which specific process model will fit best for which specific situation. This includes situations in which the sequential process is still best, as its assumptions still hold in some situations. Also, since requirements increasingly emerge from use, working on all of the requirements and solutions in advance is not feasible—which is where the ICSM Principle 2 of incremental commitment applies.

This establishes the context for the “Do everything in parallel” quote at the beginning of this chapter. Even though preferred sequential-engineering situations still exist in which “Do everything in parallel” does not universally apply, it is generally best to apply it during the first ICSM Exploratory phase. By holistically and concurrently addressing during this beginning phase all of the system’s hardware, software, human factors, and economic considerations (as described in the Wellington quote at the beginning of the chapter), projects will generally be able to determine their process drivers and best process approach for the rest of the system’s life cycle. Moreover, as discussed previously, the increasing prevalence of process drivers such as emergence, dynamism, and NDI support will make concurrent approaches increasingly dominant.

Thus suitably qualified, we can proceed to the main content of Chapter 3. Our failure and success case studies are two different sequential and concurrent approaches to a representative complex cyber–physical–human government system acquisition involving remotely piloted vehicles (RPVs). The remaining sections will discuss best practices for concurrent cyber–physical–human factors engineering, concurrent requirements and solutions engineering, concurrent development and evolution engineering, and support of more rapid concurrent engineering.

An example to illustrate ICSM concurrent-engineering benefits is the unmanned aerial system (UAS; i.e., RPV) system enhancement discussed in Chapter 5 of the NRC’s Human–System Integration report 1. These RPVs are airplanes or helicopters operated remotely by humans. The systems are designed to keep humans out of harm’s way. However, the current RPV systems are human-intensive, often requiring two people, and often considerably more, to operate a single vehicle. The increase in need to operate numerous RPVs is causing a strong desire to modify the 1:2 (one vehicle controlled by two people) ratio to allow for a single operator to operate more than one RPV, as shown in Figure 3-1.

FIGURE 3-1

FIGURE 3-1 Vision of 4:1 Remotely Piloted Vehicle System (from Pew and Mavor, 2007)

A recent advanced technology demonstration of an autonomous-agent–based system enabled a single operator to control four RPVs flying in formation to a crisis area while compensating for changes in direction to avoid adverse weather conditions or no-fly zones. Often, such demonstrations to high-level decision makers, who are typically focused on rapidly getting innovations into the competition space, will lead to commitments to major acquisitions before the technical and economic implications have been worked out (good examples have been the Iridium satellite-based personal telephone system and the London Ambulance System).

Based on our analyses of such failures and complementary successes (e.g., the rapid-delivery systems of Federal Express, Amazon, and Walmart), the failure and success stories in this chapter illustrate failure and success patterns in the RPV domain. In the future, the technical, economic, and safety challenges for similarly autonomous air vehicles will become even more complex, as with Amazon’s recent concept and prototype of filling the air with tiny, fully autonomous, battery-powered helicopters rapidly delivering packages from its warehouse to your front door.

In this chapter, the demonstration of a 4:1 vehicle:controller ratio capability highly impressed senior leadership officials viewing the demo, and they established a high-priority rapid-development program to acquire and field a common agent-based 4:1 RPV control capability for use in battlefield-based, sea-based, and home-country–based RPV operations.

3.1 Failure Story: Sequential RPV Systems Engineering and Development

This section presents a hypothetical sequential approach representative of several recent government acquisition programs, which would use the demo results to create the requirements for a proposed program that used the agent-based technology to develop a 4:1 ratio system that enabled a single operator to control four RPVs in battlefield-based, sea-based, and home-country–based RPV operations. A number of assumptions were made to sell the program at an optimistic cost of $1 billion and schedule of 40 months. Enthusiasm was such that the program, budget, and schedule were established, and a multi-service working group of experienced battlefield-based, sea-based, and home-country–based RPV controllers was established to develop the requirements for the system.

The resulting requirements included the need to synthesize status information from multiple on-board and external sensors; to perform dynamic reallocation of RPVs to targets; to perform self-defense functions; to communicate status and observational information to central commanders and other RPV controllers; to control RPVs in the same family but with different releases having somewhat different controls; to avoid harming friendly forces or noncombatants; and to be network-ready with respect to self-identification when entering battle zones, establishing security credentials and protocols, operating in a publish–subscribe environment, and participating in replanning activities based on changing conditions. These requirements were included in a request for proposal (RFP) that was sent out to prospective bidders.

The winning bidder provided an even more impressive demo of agent technology and a proposal indicating that all of the problems were well understood, that a preliminary design review (PDR) could be held in 120 days, and that the cost would be only $800 million. The program managers and their upper management were delighted at the prospect of saving $200 million of the taxpayers’ money, and they established a fixed-price contract to develop the 4:1 system to the requirements in the RFP in 40 months, with a System Functional Requirements Review (SFRR) in 60 days and a PDR in 120 days.

At the SFRR, the items reviewed were transcriptions and small elaborations of the requirements in the RFP. They did not include any functions for coordinating the capabilities, and included only sunny-day operational scenarios. There were no capabilities for recovering from outages in the network, from the loss of RPVs, or from incompatible sensor data, or for tailoring the controls to battlefield-based, sea-based, or home-country–based control equipment. The contractor indicated that it had hired some ex-RPV controllers who were busy putting such capabilities together.

However, at the PDR, the contractor could not show feasible solutions for several critical and commonly occurring scenarios, such as coping with network outages, missing RPVs, and inconsistent data; having the individual controllers coordinate with each other; performing self-defense functions; tailoring the controls to multiple equipment types; and satisfying various network-ready interoperability protocols. As has been experienced in practice 2, such capabilities are much needed and difficult to achieve.

Because the schedule was tight and the contractor had almost run out of systems engineering funds, management proposed to address the problems by using a “concurrent engineering” approach of having the programmers develop the software capabilities while the systems engineers were completing the detailed design of the hardware displays and controls. Having no other face-saving alternative to declaring the PDR to be a failure, the customers declared the PDR to be passed.

Actually, proceeding into development while completing the design is a pernicious misuse of the term “concurrent engineering,” as there is not enough time to produce feasibility evidence and to synchronize and stabilize the numerous off-nominal approaches taken by the software developers and the hardware-detail designers. The situation becomes even worse when portions of the system are subcontracted to different organizations, which will often reuse existing assets in incompatible ways. The almost-certain result for large systems is one or more off-nominal architecture-breakers that require large amounts of rework and throwaway software to reconcile the inconsistent architectural decisions made by the self-fulfilling “hurry up and code, because we will have a lot of debugging to do” programmers. Figure 3-2 shows the results of such approaches for two large TRW projects, in which 80% of the rework resulted from the 20% of problem fixes resulting from critical off-nominal architecture-breakers 3.

FIGURE 3-2

FIGURE 3-2 Results of Creating or Neglecting Off-Nominal Architecture-Breakers

As a result, after 40 months and $800 million in expenditures, some RPV control components were developed but were experiencing integration problems, and even after descoping the performance to a 1:1 operator:RPV ratio, several problems were still unresolved. For example, the hardware engineers used their traditional approach to defining interfaces in terms of message content (e.g., “The sensor data crossing an interface is defined in terms of the following units, dimensions, coordinate systems, precision, frequency, or other characteristics”). They then took full earned value credit for defining the system’s interfaces. However, the RPVs were operating in a Net-centric system of systems, where interface definition includes protocols for joining the network, performing security handshakes, publishing and subscribing to services, leaving the network, and so on. As there was no earned value left for defining these protocols, they remained undefined while the earned value system continued to indicate full credit for interface definition. The resulting rework and overruns could be said to result from off-nominal architecture breakers or from shortfalls in the concurrent engineering of the sensor data processing and networking aspects of the system, and from shortfalls in accountability for results.

Eventually, the 1:1 capability was achieved and the system delivered, but with reduced functionality, a cost of $3 billion, and a schedule of 80 months. Even worse, the hasty patching to get the first article delivered left the customer with a brittle, poorly documented, poorly tested system that would be the source of many expensive years of system ownership and sub-par performance.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020