Variability in Software Product Lines, CMU/SEI-2005-TR-012, 2005. For each tactics question, ll the Supported column with Y if the tactic is supported in the architecture and with N otherwise. For example: 1. In Kubernetes, nodes (hardware or VMs) contain Pods, and Pods contain containers, as shown in Figure 16.4. However, it also admits the possibility that a lower-priority, but still important request might take an arbitrarily long time to be serviced, because it is stuck behind a series of higher-priority requests. [Xiao 16] L. Xiao, Y. Cai, R. Kazman, R. Mo, and Q. Feng. While this might be considered to be a subcase of behavioral semantics, it is so important (and often subtle) that we call it out explicitly. This connection has resulted in standard patterns to support user interface design. You then elaborate on this root node by listing the major QAs that the system is required to exhibit. In such cases, the parameters may be relaxed to re ect this possibility and avoid triggering unnecessary recovery actions. 817, https://doi.org/10.1145/62546.62549. 13.6 Discussion Questions 1. Setting and examining a programs internal state is an aspect of testing that will gure prominently in our tactics for testability. Such interactions are represented as connectors in C&C views. The work-breakdown structure in turn dictates units of planning, scheduling, and budget; interteam communication channels; con guration control and le-system organization; integration and test plans and procedures; and even project minutiae such as how the project intranet is organized and who sits with whom at the company picnic. 3. These are the measurements in the long tail on the right side of the histogram. This suggests keeping data on the cloud is a good ideabut then all the interactions between the cloud and the application need to be tested. Traceability Architecture, of course, does not live in a bubble, but in a milieu of information about the system under development that includes requirements, code, tests, budgets and schedules, and more. The results of ADD cannot be good if the inputs are poorly formed. The frequency of heartbeats determines the time for detection of a fault. In this important but often overlooked structure, the units are also modules, and perhaps classes. The new component is integrated into the system and deployed in 1 month, with no more than 1 person-month of e ort. Table 25.1 Technical Duties of a Software Architect Table 25.2 Nontechnical Duties of a Software Architect Architects also routinely perform many other duties, such as leading code reviews or getting involved in test planning. [Hohpe 20] Gregor Hohpe. Provide a centralized resource to analyze and help with architecture tools. Improve your nontechnical skills. You can read about SAFe at scaledagileframework.com/. The techniques outlined in this chapter are intended to discover possible hazards that could result from the systems operation and help in creating strategies to cope with these hazards. [Mo 15] R. Mo, Y. Cai, R. Kazman, and L. Xiao. Testability 13. The VoI technique is used to calculate the expected gain from a reduction in the uncertainty surrounding a decision through some form of data collection exercisein this case, the construction of prototypes. (However, this terminology is not always followed in practice.) The one exception to invertibility is the READ operation: Since measurement is destructive, the result of a READ operation does not allow the recovery of the original qubit. Nevertheless, some say that security and usability go (or should go) hand in hand, and argue that making the system easy to use securely is the best way to promote security to the users. Encapsulation may also hide interfaces that are not relevant for a particular integration task. Service dependencies are acyclic. Improving business processes 10. It is important to establish clear criteria that will allow a driver to be moved to the Partially Addressed or Completely Addressed columns. Finally, the analytic redundancy tactic permits not only diversity of components, but also a higher-level diversity that is visible at the input and output level. Recovery The nal category of safety tactics is recovery, which acts to place the system in a safe state. Thus, considering energy e ciency as a rst-class quality attribute is important for the following reasons: 1. And yet for all the ways that an exercise might go terribly wrong, for all the details that can be overlooked, for all the fragile egos that can be bruised, and for all the high stakes that are on the table, we have never had an architecture evaluation exercise spiral out of control. This death by a thousand cuts is common on software projects. Forcing the user to change those settings will prevent attackers from gaining access to the system through settings that may be publicly available. The DMZ sits between the Internet and an intranet, and is protected by a pair of rewalls, one on either side. Users may or may not know that they are being used as guinea pigser, that is, canaries. Many concerns that drive an architecture do not manifest themselves at all as observables in the system being speci ed, and so are not the subject of requirements speci cations. Return messages go directly from the service instances to the clients (determined by the from eld in the IP message header), bypassing the load balancer. In all modern systems, elements interact with each other by means of interfaces that partition details about an element into public and private parts. While it is common to omit one or more of these six parts, particularly in the early stages of thinking about quality attributes, knowing that all of the parts are there forces the architect to consider whether each part is relevant. This kind of mismatch is typically di cult to observe and predict, although the analysts life is improved somewhat if the elements involved employ metadata. Problems with system values. The allowedto-use relationship among the layers is subject to a key constraint: The relations must be unidirectional. Table 21.3 A Typical Agenda for Lightweight Architecture Evaluation There is no nal report, but (as in the ATAM) a scribe is responsible for capturing results, which can then be shared and serve as the basis for risk remediation. It also means considering whether the design purpose has been achieved or if additional design rounds are needed in future project increments. The executives, it turned out, were busy just now, so could we come back and meet with them a bit later? 4. 3.8 For Further Reading Some extended case studies showing how tactics and patterns are used in design can be found in [Cervantes 16]. The system processes all of the requests with an average latency of two seconds. The Internet Engineering Task Force has promulgated a number of standards supporting availability tactics. This design concept does not prescribe a particular structure. This issue is tied to available display resolution. Find step-by-step solutions and answers to Computer Security: Principles And Practice ( Edition) - 9780134794105, as well as thousands of textbooks so you can move forward with confidence. [Gajjarby 17] Manish J. Gajjarby. 21.9 Discussion Questions 1. There is a strong connection between the achievement of usability and modi ability. Until then, keep these examples in mind as a starting point: If your system requires high performance, then you need to pay attention to managing the time-based behavior of elements, their use of shared resources, and the frequency and volume of their interelement communication. MBSE per se is beyond the scope of this book, but we cant help but notice that what is being modeled is architecture. This tactic checks the validity or reasonableness of speci c operations or outputs of a component. 9 (1994): 87101. [Bachmann 05] F. Bachmann and P. Clements. What should you do? Revoke access. Software Product Lines. Address: Be the first to receive exclusive offers and the latest news on our products and services directly in your inbox. The technical, economic, and philosophical justi cations for your projects requirements practices are beyond the scope of this book. Sni ng out ASRs from a Requirements Document While requirements documents wont tell an architect the whole story, they are still an important source of ASRs. 4. Of course, the humans dont always get it right when the computers get it wrong. Safety is concerned with a systems ability to avoid straying into states that cause or lead to damage, injury, or loss of life to actors in its environment. This tactic is intended to tolerate speci cation errors by using separate requirement speci cations. 6. The plug-ins can be developed by di erent teams or organizations than the developers of the microkernel. Having multiple versions of the same service in operation, however, may introduce version incompatibilities. All. The cooperating elements must agree on assumptions about shared resources. Table 25.3 Skills of a Software Architect Knowledge A competent architect has an intimate familiarity with an architectural body of knowledge. Safety 11. Second, lists often generate more controversy than understanding. The Duties, Skills, and Knowledge of Software Architects, Proceedings of the Working IEEE/IFIP Conference on Software Architecture, 2007. Escalating restart. Services get events from other services. Implementation bugs should be xed by adding the usage failure scenario as an additional test case to avoid regressions. Connectors are the communication vehicles among components, such as call-return, process synchronization operators, pipes, or others. Table 25.4 gives a set of knowledge areas for an architect. Clients must be designed so that they resend a request if they do not receive a timely response, allowing the load balancer to distribute the request to a di erent service instance. VM images can be created by various techniques for provisioning, including using operating system functions or loading a pre-created image. Although one might conceivably describe all possible traces to generate the equivalent of a comprehensive behavioral model, trace-oriented documentation does not really seek to do so. This is done to reduce the container load timeyour service is constrained to be a thin image layer on top of the providers base image layer. Error Handling When designing an interface, architects naturally concentrate on how it is supposed to be used in the nominal case, when everything works according to plan. Authorization means ensuring that an authenticated actor has the rights to access and modify either data or services. Detect intrusion. Architecture tells implementers which modules to implement and how those modules are wired together. The scenario techniques we introduced for software QAs work equally well for system QAs. Processor sharing is achieved through a thread-scheduling mechanism. When the analysis is complete, the evaluation team examines the full set of discovered risks to look for overarching themes that identify systemic weaknesses in the architecture or even in the architecture process and team. Unfortunately, this is not usually the case, although information in the requirements documents can certainly be useful. . What happens when the mode select button is pushed? interrupted one of the audience members. The Role of Architects in Projects 24.1 The Architect and the Project Manager 24.2 Incremental Architecture and Stakeholders 24.3 Architecture and Agile Development 24.4 Architecture and Distributed Development 24.5 Summary 24.6 For Further Reading 24.7 Discussion Questions 25. So an interface is more than what is provided by an element; an interface also includes what is required by an element. Are there any? Look up recovery point objective (RPO) and recovery time objective (RTO) and explain how these can be used to set a checkpoint interval when using the rollback tactic. We will discuss architectural tactics and patterns in Part 2. The accuracy of the analysis and expected degree of con dence in the analysis results will vary according to the maturity of the available artifacts. The levels and boundaries between them may vary depending on the system, but they are implied in several reference processes and standards such as Automotive SPICE. A criterion for Completely Addressed may be, for example, that the driver has been analyzed or that it has been implemented in a prototype, and you determine that the requirements for that driver have been satis ed. For example, if an organization is using an o -premises cloud, it might not have direct access to real-time energy data. A parameterized function f(a, b) is more general than the similar function f(a) that assumes b = 0. CH01-Comp Sec 4e - Lecture notes Chapter 1 - Computer Security: Principles and Practice ####### - Studocu Chapter 1 Slides computer security: principles and practice fourth edition : william stallings and lawrie brown chapter overview the nist report nistir 7298 ( Skip to document Ask an Expert Sign inRegister Sign inRegister Home Ask an ExpertNew C&C structures help answer questions such as the following: What are the major executing components and how do they interact at runtime? What insight did these questions provide into the design decisions made (or not made)? This is what gives the model its power. There are three approaches you can follow to create a new VM image: 1. Author James Gleick (A Bug and a Crash, around.com/ariane.html) writes that It took the European Space Agency 10 years and $7 billion to produce Ariane 5, a giant rocket capable of hurling a pair of three-ton satellites into orbit with each launch. The architect needs to determine which states of the system can safely support an update. That is, a message goes through a hierarchy of load balancers before arriving at the service instance. Since they are compiled by language-speci c compilers, the speci cation is necessary to ensure correct behavior of the interface. The performance community has events arriving at a system, the security community has attacks arriving at a system, the availability community has faults arriving, and the usability community has user input. All of these may actually refer to the same occurrence, but they are described using di erent terms. Separating di erent entities limits the scope of an attack. Such states and modes may, in some cases, be explicitly captured in protocols. This introduces a requirement for catalogs and databases of interfaces to assist in maintaining intellectual control. A module might take the form of a class, a collection of classes, a layer, an aspect, or any decomposition of the implementation unit. [Grinter 99] Rebecca E. Grinter. Communication diagrams are useful when the task is to verify that an architecture can ful ll the functional requirements. The Janitor Monkey ensured that the Net ix cloud environment was running free of clutter and waste. This gives us a weighting for each anti-pattern in terms of its contribution to architecture debt. The limiting factor on the size of a data center is the electric power it consumes and the amount of heat that the equipment produces: There are practical limits to bringing electrical power into the buildings, distributing it to the equipment, and removing the heat that the equipment generates. Projects likely already have issue tracking systems and revision histories, and plenty of reverse-engineering tools are available, including open source options. This tactic attempts to deal with the systematic nature of design faults by adding diversity to redundancy. That is, given a set of required functionality, there is no end to the architectures you could create to satisfy that functionality. The builder takes as input a description of the designed UI produced through direct manipulation techniques and which may then produce source code. Learning tools offered by Pearson+ include eTextbook plans and Channels video subscriptions. [Kazman 04] R. Kazman, P. Kruchten, R. Nord, and J. Tomayko. Documenting patterns. In many projects, these are must-have capabilities, so the purchase price of the tool which is not insigni cant in some cases should be evaluated against what it would cost the project to achieve these capabilities on its own. Like VMs and VM images, containers are packaged into executable container images for transfer. Within 10 meters. Multiple interfaces provide a kind of separation of concerns. That is, the client should not assume that the server has retained any information about the clients last request. Layers Pattern The layers pattern divides the system in such a way that the modules can be developed and evolved separately with little interaction among the parts, which supports portability, modi ability, and reuse. For example, we say that module A is dependent on component B if A calls B, if A inherits from B, or if A uses B. All of these uses depend on monitoring the current state of the battery. . Performance is often linked to scalabilitythat is, increasing your systems capacity for work, while still performing well. The Definitive, Practical, Proven Guide to Architecting Modern Software--Now Fully Updated There are limits to what can be achieved with vertical scaling. The rst category deals with adding controllability and observability to the system. Burt Rutan A substantial portion of the cost of developing well-engineered systems is taken up by testing. The melancholy fact is that operations on computers take time. Factors in Software Quality. 22.11 For Further Reading Documenting Software Architectures: Views and Beyond [Clements 10a] is a comprehensive treatment of the architecture documentation approach described in this chapter. More scenarios might be analyzed during this period, if desired, or answers to questions posed in phase 1 may be clari ed. For example, a request for a modi cation that arrives after the code has been frozen for a release may be treated di erently than one that arrives before the freeze. The Information Technology Architecture Body of Knowledge (ITABoK) is a free public archive of IT architecture best practices, skills, and knowledge developed from the experience of individual and corporate members of Iasa, the worlds largest IT architecture professional organization (https://itabok.iasaglobal.org/itabok/). 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