Questions and Answers of Software Architecture In Practice

For that QA, assemble a set of specific scenarios that describe what you mean by it. Use that set of scenarios to construct a general scenario for it.
For the QA you chose for question 2, assemble a set of design mechanisms (patterns and tactics) that help you achieve it.Data from Question 2For that QA, assemble a set of specific scenarios that
Repeat questions 2 and 3 for the QA of development cost, and then for the QA of operating cost.Data from Question 2For that QA, assemble a set of specific scenarios that describe what you mean by it.
What might cause you to add a tactic or pattern to the sets of QAs already described (or any other QA, for that matter)?
Section 18.5 discussed several aspects of testing that are more challenging in mobile systems. What testability tactics from can help with these issues?
Is architecture debt more or less detrimental than other kinds of debt, such as code debt, documentation debt, or testing debt?
Aircraft have architectures that can be characterized by how they resolve some major design questions, such as engine location, wing location, landing gear layout, and more. For many decades, most
What is architecture’s role in project risk reduction?
Sailing ships have architectures, which means they have “structures” that lend themselves to reasoning about the ship’s performance and other quality attributes. Look up the technical
Prioritize the list of 13 reasons in this chapter according to some criteria that are meaningful to you. Justify your answer. Or, if you could choose only two or three of the reasons to promote the
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.
Write a set of concrete scenarios for deployability using each of the possible responses in the general scenario.
Write a concrete deployability scenario for the software for a car (such as a Tesla).
Write a concrete deployability scenario for a smartphone app. Now write one for the server-side infrastructure that communicates with this app.
If you needed to display the results of a search operation, would you perform A/B testing or simply use the color that Google has chosen? Why?
Which structures would be involved in implementing the package dependencies tactic? Would you use the uses structure? Why or why not? Are there other structures you would need to consider?
Which structures would be involved in implementing the manage service interactions tactic? Would you use the uses structure? Why or why not? Are there other structures you would need to consider?
Under what circumstances would you prefer to roll forward to a new version of service, rather than to roll back to a prior version? When is roll forward a poor choice?
Write a set of concrete scenarios for energy efficiency using each of the possible responses in the general scenario.
Create a concrete energy efficiency scenario for a smartphone app (for example, a health monitoring app).
Create a concrete energy efficiency scenario for a cluster of data servers in a data center. What are the important distinctions between this scenario and the one you created for question 2?Data from
Enumerate the energy efficiency techniques that are currently employed by your laptop or smartphone.
What are the energy tradeoffs in your smartphone between using Wi-Fi and the cellular network?
Calculate the amount of greenhouse gases in the form of carbon dioxide that you, over an average lifetime, will exhale into the atmosphere. How many Google searches does this equate to?
Suppose Google reduced its energy usage per search by 1 percent. How much energy would that save per year?
How much energy did you use to answer question 7?Data from in question 7Suppose Google reduced its energy usage per search by 1 percent. How much energy would that save per year?
Think about an integration that you have done in the past—perhaps integrating a library or a framework into your code. Identify the various “distances” that you had to deal with. Which of these
Write a concrete integrability scenario for a system that you are working on (perhaps an exploratory scenario for some component that you are considering integrating).
Which of the integrability tactics do you think would be the easiest to implement in practice, and why? Which would be the most difficult, and why?
Many of the integrability tactics are similar to the modifiability tactics. If you make your system highly modifiable, does that automatically mean that it will be easy to integrate into another
A standard use of SOA is to add a shopping cart feature to an e-commerce site. Which commercially available SOA platforms provide different shopping cart services? What are the attributes of the
Write a program that accesses the Google Play Store, via its API, and returns a list of weather forecasting applications and their attributes.
Sketch a design for a dynamic discovery service. Which types of distances does this service help to mitigate?
In the list you compiled for question 1, which tactics and patterns are especially helpful for each?Data from Question 1Modifiability comes in many flavors and is known by many names; we discussed a
In many laundromats, washing machines and dryers accept coins but do not give change. Instead, separate machines dispense change. In an average laundromat, there are six or eight washers and dryers
For the laundromat in question 4, describe the specific form of modifiability (using a modifiability scenario) that seems to be the aim of arranging the machines as described.Data from Question 4In
A wrapper, introduced in Chapter 7, is a common architectural pattern to aid modifiability. Which modifiability tactics does a wrapper embody?
Other common architectural patterns that can increase a system’s modifiability include blackboard, broker, peer-to-peer, model-view-controller, and reflection. Discuss each in terms of the
“Every system has real-time performance constraints.” Discuss. Can you provide a counterexample?
Write a concrete performance scenario that describes the average on-time flight arrival performance for an airline.
Write several performance scenarios for an online auction site. Think about whether your major concern is worst-case latency, average-case latency, throughput, or some other response measure. Which
Web-based systems often use proxy servers, which are the first element of the system to receive a request from a client (such as your browser). Proxy servers are able to serve up often-requested
A fundamental difference between interaction mechanisms is whether interaction is synchronous or asynchronous. Discuss the advantages and disadvantages of each with respect to each of these
Find physical-world (that is, non-software) examples of applying each of the manage resources tactics. For example, suppose you were managing a brick-and-mortar big-box retail store. How would you
List 10 computer-controlled devices that are part of your everyday life right now, and hypothesize ways that a malicious or malfunctioning system could use them to hurt you.
Write a safety scenario that is designed to prevent a stationary robotic device (such as an assembly arm on a manufacturing line) from injuring someone, and discuss tactics to achieve it.
The U.S. Navy’s F/A-18 Hornet fighter aircraft was one of the early applications of fly-by-wire technology, in which onboard computers send digital commands to the control surfaces (ailerons,
According to slate.com and other sources, a teenage girl in Germany “went into hiding after she forgot to set her Facebook birthday invitation to private and accidentally invited the entire
Write a safety scenario to protect the unfortunate girl in Germany from Facebook.
On February 25, 1991, during the Gulf War, a U.S. Patriot missile battery failed to intercept an incoming Scud missile, which struck a barracks, killing 28 soldiers and injuring dozens. The cause of
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
Discuss how you think safety tends to “trade off” against the quality attributes of performance, availability, and interoperability.
Discuss the relationship between safety and testability.
What is the relationship between safety and modifiability?
With the Air France flight 447 story in mind, discuss the relationship between safety and usability.
Create a list of faults or a fault tree for an automatic teller machine. Include faults dealing with hardware component failure, communications failure, software failure, running out of supplies,
Write a set of concrete scenarios for security for an automobile. Consider in particular how you would specify scenarios regarding control of the vehicle.
One of the most sophisticated attacks on record was carried out by a virus known as Stuxnet. Stuxnet first appeared in 2009, but became widely known in 2011 when it was revealed that it had
Security and usability are often seen to be at odds with each other. Security often imposes procedures and processes that seem like needless overhead to the casual user. Nevertheless, some say that
List some examples of critical resources for security, which a DoS attack might target and try to exhaust. Which architectural mechanisms could be employed to prevent this kind of attack?
Which of the tactics detailed in this chapter will protect against an insider threat? Can you think of any that should be added?
In the United States, Netflix typically accounts for more than 10 percent of all Internet traffic. How would you recognize a DoS attack on Netflix.com? Can you create a scenario to characterize this
The public disclosure of vulnerabilities in an organization’s production systems is a matter of controversy. Discuss why this is so, and identify the pros and cons of public disclosure of
Similarly, the public disclosure of an organization’s security measures and the software to achieve them (via open source software, for example) is a matter of controversy. Discuss why this is so,
A testable system is one that gives up its faults easily. That is, if a system contains a fault, then it doesn’t take long or much effort to make that fault show up. In contrast, fault tolerance is
What other quality attributes do you think testability is most in conflict with? What other quality attributes do you think testability is most compatible with?
Many of the tactics for testability are also useful for achieving modifiability. Why do you think that is?
Write some concrete testability scenarios for a GPS-based navigation app. What tactics would you employ in a design to respond to these scenarios?
Write a concrete usability scenario for your automobile that specifies how long it takes you to set your favorite radio stations. Now consider another part of the driver experience and create
One of our tactics is to limit nondeterminism, and one method is to use locking to enforce synchronization. What impact does the use of locks have on other quality attributes?
Suppose you’re building the next great social networking system. You anticipate that within a month of your debut, you will have half a million users. You can’t pay half a million people to test
Suppose you use executable assertions to improve testability. Make a case for, and then a case against, allowing the assertions to run in the production system as opposed to removing them after
How might usability trade off against security? How might it trade off against performance?
Pick a few of your favorite websites that do similar things, such as social networking or online shopping. Now pick one or two appropriate responses from the usability general scenario (such as
Why is it that in so many systems, the cancel button in a dialog box appears to be unresponsive? Which architectural principles do you think were ignored in these systems?
Why do you think that progress bars frequently behave erratically, moving from 10 to 90 percent in one step and then getting stuck on 90 percent?
Research the crash of Air France flight 296 into the forest at Habsheim, France, in 1988. The pilots said they were unable to read the digital display of the radio altimeter or hear its audible
The Kingdom of Bhutan measures the happiness of its population, and government policy is formulated to increase Bhutan’s GNH (gross national happiness). Read about how the GNH is measured
Discuss how you think development distributability tends to trade off against the QAs of performance, availability, modifiability, and integrability.
Research some QA lists for things that are not software systems: qualities of a good car, for example, or a good person to be in a relationship with. Add qualities of your own choosing to the list or
Development-time tactics have to do with separating and encapsulating responsibilities. Performance tactics have to do with putting things together. That is why they are perpetually in conflict. Must
Is there a taxonomy of tactics? Chemists have the periodic table and laws of molecular interaction, atomic physicists have their catalogs of subatomic particles and laws for what happens when they
Security is a QA that is especially sensitive to processes that take place in the physical world outside the computer: processes for applying patches, processes for choosing and safeguarding your
What is the relationship between each pair of QAs in the following list?• Performance and security• Security and buildability• Energy efficiency and time to market
Describe the interface to a dog, or another kind of animal with which you are familiar. Describe its operations, events, and properties. Does a dog have multiple interfaces (e.g., one for a known
Document the interface to a light bulb. Document its operations, events, and properties. Document its performance and resource utilization. Document any error states it may enter and what the result
Under what circumstances should performance (e.g., how long an operation takes) be a part of an element’s published interface? Under what circumstances should it not?
Suppose an architectural element will be used in a high-availability system. How might that affect its interface documentation? Suppose the same element will now be used in a high-security system.
The section “Error Handling” listed a number of different error-handling strategies. For each, when is its use appropriate? Inappropriate? What quality attributes will each enhance or diminish?
What would you have done to prevent the interface error that led to the loss of the Mars Climate Orbiter, as described at the beginning this chapter?
On June 4, 1996, an Ariane 5 rocket failed quite spectacularly, only 37 seconds after launch. Research this failure, and discuss what better interface discipline could have done to prevent it.
A database schema represents an interface between an element and a database; it provides the metadata for accessing the database. Given this view, schema evolution is a form of interface evolution.
Create a LAMP container using Docker. Compare the size of your container image to one you find on the Internet. What is the source of the difference? Under what circumstances is this a cause of
Calculate the cost of an ATAM-based evaluation for a large enterprise-scale system’s architecture. Assume a fully burdened labor rate of $250,000 per year for the participants. Assuming that an
Find a commonly accepted definition of system architecture and discuss what it has in common with software architecture. Do the same for enterprise architecture.
If you remember nothing else from this book, remember . . . what? Extra credit for not peeking
For each of the 13 reasons why architecture is important articulated in this chapter, take the contrarian position: Propose a set of circumstances under which architecture is not necessary to achieve
This chapter argues that architecture brings a number of tangible benefits. How would you measure the benefits, on a particular project, of each of the 13 points?
Suppose you want to introduce architecture-centric practices to your organization. Your management is open to the idea, but wants to know the ROI for doing so. How would you respond?
Do you suppose that the set of tactics for a quality attribute is finite or infinite? Why?

Showing 1 - 100 of 166