A Review of the Next Generation Air Transportation System Implications and Importance of System Architecture (2015) / Chapter Skim
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2 Assert Architectural Leadership
2 Assert Architectural Leadership
Pages 24-48
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From page 24... ...
Accordingly, and consistent with other elements of its task, such as software development,3 the committee 1 The Office of Management and Budget (OMB) requires that every federal agency have an enterprise architecture designed to "promote mission success by serving as an authoritative reference, and by promoting functional integration and resource optimization with both i nternal and external service partners" (OMB, "The Common Approach to Federal Enterprise Architecture," Washington, D.C., May 2, 2012, http://www.whitehouse.gov/sites/ default/files/omb/assets/egov_docs/common_approach_to_federal_ea.pdf, p.
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From page 25... ...
This chapter discusses the committee's assessment of the Federal Aviation Administration's (FAA's) current architectural approach for NextGen, key elements of architectural leadership, and recommendations for change.
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. The enterprise architecture "describes the enterprise that directly supports operational air traffic services" and "describes the enterprise that supports FAA administrative operations."4 Parts of the enterprise architecture 4 Remarks from FAA briefing "Role of Enterprise Architecture NextGen: Briefing to ational N Research Council" to study committee, March 2013.
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From page 27... ...
A close reading of architecture description standards, such as the Department of Defense Architecture Framework, will show that this issue was recognized by the description standard authors. Such frameworks are careful to identify the need for an architecture team to identify the purpose of the system, the purpose of the architecture, the information needed, and only then fold that information into standardized document products.
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These views provide overviews and details aimed at specific stakeholders. In addition to the views provided by DoDAF -- all view, systems view, operational view, and technical view -- the NextGen enterprise architecture provides for two additional views that are important for acquisition.
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Nor is it clear that the abstractions generated are sufficient to describe the 9 National Research Council (NRC) , Interim Report of a Review of the Next Generation Air Transportation System Enterprise Architecture, Software, Safety, and Human Factors, The National Academies Press, Washington, D.C., 2014.
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The commitments also include expectations regarding performance, security, and other behavioral characteristics of the constituent components of a system, such that an overall architectural model can facilitate prediction of significant quality-related characteristics of a system that is consistent with the architectural model. Architecture represents the earliest and often most important design decisions -- those that are the hardest to change and the most critical to get right.
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From page 31... ...
The lack of a well-defined, sufficiently deeply decomposed system architecture for NextGen poses at least two serious problems. First, the fact that the architecture description is insufficiently deeply defined means that the specifications for the system's component parts continued
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Moreover, it is not clear how or if there are systems engineering work products that are derived from the midterm architecture. As one example, the committee noted that the first architecture rule written in the AV-1 "Mid-Term Overview and Summary Information" document states that NAS [enterprise architecture]
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From page 33... ...
With regard to data alone, NextGen has to cope with a range of information from weather data to flight plans to real-time traffic data to emergency declarations. In both cases, the building archi tecture and the NextGen system architecture, different notations and formalisms may be used to support specification of the different kinds of architectural features.
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The committee urges a focus on system architecture that reflects a set of fundamental, structural decisions about a system and that is distinguished from the architecture description, a document that records those decisions (much like the FAA uses the enterprise architecture)
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Modern software architecture standards all call for a "data view" or "logical view" or something equivalent. This is usually conceived of as an implementation-independent definition of core data, which is transformed into physical data models during implementation.
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14 This statement suggests that the NextGen organization provides little architectural direction to the enterprise. Although the choice above may in the end be a plausible architectural decision, the committee is concerned that this choice is being made by default rather than the result of a considered process through trades on the bases of explicitly stated criteria.15 Moreover, insufficient abstractions to high-level services place roadblocks in the way of those attempting to insert new technologies or services (such as unmanned aircraft systems (UAS)
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But ERAM relies on complex 17 NRC, Pre-Milestone A and Early-Phase Systems Engineering, 2008. 18 The fire at Chicago Air Route Traffic Control Center in September 2014 provides further evidence of an architectural resilience failure in the NAS architecture.
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The extensive number of routings that would have been required to de-conflict the aircraft with lower-altitude flights used a large amount of available memory and interrupted the computer's other flight-processing functions.1 Because ERAM is a major NextGen program, the committee asked for infor mation about this failure in order to better understand how such failures come about, how they are handled, and what improvements with regard to architecture and software development the committee could suggest.2 While not tasked with undertaking a complete analysis of this or any other specific incident, the com mittee offers the following limited analysis -- based on necessarily limited data -- of why such failures are a concern and how appropriate system architecture and software development approaches could help reduce the likelihood of such failures in the future. First, it should be noted that this incident led to a considerable loss of air traffic control service.
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2 FAA, "ZLA Air Traffic Control (ATC) - Summary of Events Surrounding Declaration of ATC Zero at ZLA," 2014; received following committee inquiry.
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Elements of Architectural Leadership Any large-scale, software-intensive systems endeavor requires a system architecture that specifies how all of its parts fit together and interact, and which can be used in a dynamic way to help inform and drive plan
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• Architectural leadership at the system-of-systems level to help maintain appropriate alignment among the various architectural perspectives and to ensure that as requirements change and development proceeds that the architecture is kept consistent. • Thoughtful and consistent attention to ensuring that the system architecture is flexible and evolvable.19 While modernization and incremental improvements proceed, care should be taken to ensure that the architecture does not become too rigid such that innovative changes cannot be put in place later on.
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Instead, the committee has focused on the importance of a suitable architectural approach -- regardless of which key performance parameters are chosen -- to make progress. A stronger architectural foundation will also make it possible to explore the relationship between the key parameters and the system design.
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Developing an effective architectural leadership team is more of a selection and hiring challenge than it is a training issue. Major software companies and system integrators have highly evolved career paths, mentoring programs, and peer selection boards in place to identify, develop, and certify qualified architects.
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One downside of advisory panels as typically structured is that they do not have an explicit stake in the outcome of the development or responsibility to stay with an effort if it goes astray. In whatever form it takes, an architecture leadership community is a locus within which to accomplish the following: • Provide leadership regarding requirements negotiation, acquisition, budgeting, verification and validation, testing and certification, acceptance, integration, and key changes and their anticipated effects on the system as a whole.
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From page 45... ...
• Determine appropriate approaches to information hiding and abstraction to support basic system infrastructure services. For example, the NextGen architecture does not address availability or cybersecurity in a comprehensive way, which in part derives from this lack of infrastructure abstraction.24 By abstracting infrastructure aggressively, the system avoids reliance on particular hardware choices, but can instead allow the hardware (and some systems layers above, perhaps)
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Balance with regard to both documentation and technical commitments is important. Finding an appropriate balance between the level of specific technical commitment in a system-architectural model (with all the benefits of fixing on particular choices in this regard)
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The architectural leadership should be responsible for balancing tensions among a number of competing goals, such as innovation and stability or safety, value delivered and costs incurred, security and openness, uncertainty and predictability, process maturity and agility, and so on -- avoiding an excessively bureaucratic process- and document-bound approach while providing sufficient leadership and direction. Governance will be needed to facilitate an effective process by which issues can be raised, debated, decided, recorded, and implemented.
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From page 48... ...
should initiate, grow, and engage a capable architecture ommunity -- leaders c and peers within and outside FAA -- who will expand the breadth and depth of expertise that is steering architectural changes. Recommendation: The Federal Aviation Administration should conduct a small number of experiments among its system integra tion partners to prototype candidate solutions for establishing and managing a vibrant architectural community.
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