1.For each of the following kinds of errors, define the error type and give an a
ID: 3697347 • Letter: 1
Question
1.For each of the following kinds of errors, define the error type and give an actual occurrence of an error of that type: data-entry error, data-retrieval error, software bug.
2. Explain the mistakes that led to the failure of the Patriot missile system.
3. Explain the mistakes that led to the failure of the AT&T long-distance network.
4. Explain the error that caused NASA’s Mars Climate Orbiter to crash. 18. What evidence is there that software quality is improving?
5. Explain how computer simulations are validated.
6. Explain why the courts reached different conclusions about the validity of software licenses in Step-Saver Data Systems v. Wyse Technology and The Software Link and Mortenson v. Timberline Software.
Explanation / Answer
1.
A transcription error is a specific type of data entry error that is commonly made by human operators or by optical character recognition programs (OCR). When humans do data entry, errors are therefore expected. Unfortunately, data entry errors can have devastating effects on research results. Simple data entryerrors – such as typing an incorrect number, typing a number twice, or skipping a line – can ruin the results of a statistical analysis.
data retrieval The process by which data is selected and extracted from a file, a group of files, or a database.when ever we want to try to retrieve the information using the input and the output is displayed without the input information is called the data retrieval error.
software bug: A software bug is an error, flaw, failure or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.
A software bug is a problem causing a program to crash or produce invalid output. The problem is caused by insufficient or erroneous logic. A bug can be an error, mistake, defect or fault, which may cause failure or deviation from expected results. Most bugs are due to human errors in source code or its design.
2. failure of the Patriot missile system:
It turns out that the cause was an inaccurate calculation of the time since boot due to computer arithmetic errors. Specifically, the time in tenths of second as measured by the system's internal clock was multiplied by 1/10 to produce the time in seconds. This calculation was performed using a 24 bit fixed point register. In particular, the value 1/10, which has a non-terminating binary expansion, was chopped at 24 bits after the radix point. The small chopping error, when multiplied by the large number giving the time in tenths of a second, lead to a significant error. Indeed, the Patriot battery had been up around 100 hours, and an easy calculation shows that the resulting time error due to the magnified chopping error was about 0.34 seconds
A Scud travels at about 1,676 meters per second, and so travels more than half a kilometer in this time. This was far enough that the incoming Scud was outside the "range gate" that the Patriot tracked. Ironically, the fact that the bad time calculation had been improved in some parts of the code, but not all, contributed to the problem, since it meant that the inaccuracies did not cancel.
The range gate's prediction of where the Scud will next appear is a function of the Scud's known velocity and the time of the last radar detection. Velocity is a real number that can be expressed as a whole number and a decimal. Time is kept continuously by the system's internal clock in tenths of seconds but is expressed as an integer or whole number. The longer the system has been running, the larger the number representing time. To predict where the Scud will next appear, both time and velocity must be expressed as real numbers. Because of the way the Patriot computer performs its calculations and the fact that its registers are only 24 bits long, the conversion of time from an integer to a real number cannot be any more precise than 24 bits.
This conversion results in a loss of precision causing a less accurate time calculation. The effect of this inaccuracy on the range gate's calculation is directly proportional to the target's velocity and the length of the the system has been running. Consequently, performing the conversion after the Patriot has been running continuously for extended periods causes the range gate to shift away from the center of the target, making it less likely that the target, in this case a Scud, will be successfully intercepted.
3.the failure of the AT&T long-distance network
The fault was in the code" of the new software that AT&T loaded into front-end processors of all 114 of its 4ESS switching systems in mid-December, said Larry Seese, AT&T's director of technology development.
The problem began and when a piece of trunk interface equipment developed internal problems for reasons that have yet to be determined. The equipment told the 4ESS switch in New York that it was having problems and couldn't correct the fault. "The recovery code is written so that the processor will run corrective initialization on the equipment. That takes four to six seconds. At the same time, new calls are stopped from coming into the switch.
message as a "congestion signal." After the switch successfully completed the reintialization, the New York switch went back in service and began processing calls. That is when the fault in the new software reared its ugly head. Under the previous system, switch A would send out a message that it was working again, and switch B would double-check that switch A was back in service. With the new software, switch A begins processing calls and sends out call routing signals. The reappearance of traffic from switch A is supposed to tell switch B that A is working again.
The event just repeated itself in every switch over and over again. If the switches hadn't gotten a second message while resetting, there would have been no problem. If the messages had been received farther apart, it would not have triggered the problem."
AT&T solved the problem by reducing the messaging load of the CCS7 network. That allowed the switches to rest themselves and the network to stabilize.
4. error that caused NASA’s Mars Climate Orbiter to crash.
The primary cause of this discrepancy was that one piece of ground software supplied by Lockheed Martin produced results in a United States customary unit, contrary to its Software Interface Specification (SIS), while a second system, supplied by NASA, expected those results to be in SI units, in accordance with the SIS. Specifically, software that calculated the total impulse produced by thruster firings calculated results in pound-seconds. The trajectory calculation software then used these results -- expected to be in newton-seconds -- to update the predicted position of the spacecraft.
The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed. A meeting of trajectory software engineers, trajectory software operators (navigators), propulsion engineers, and managers, was convened to consider the possibility of executing Trajectory Correction Maneuver-5, which was in the schedule. Attendees of the meeting recall an agreement to conduct TCM-5, but it was ultimately not done.
That probably stopped the engine from completing its burn, so Climate Orbiter likely plowed through the atmosphere, continued out beyond Mars and now could be orbiting the sun.
Climate Orbiter was to relay data from an upcoming partner mission called Mars Polar Lander, scheduled to set down on Mars in December. Now mission planners are working out how to relay its data via its own radio and another orbiter now circling the red planet.
Climate Orbiter and Polar Lander were designed to help scientists understand Mars' water history and the potential for life in the planet's past. There is strong evidence that Mars was once awash with water, but scientists have no clear answers to where the water went and what drove it away.
NASA has convened two panels to look into what led to the loss of the orbiter, including the internal peer review panel that released the Thursday finding. NASA also plans to form a third board -- an independent review panel -- to look into the accident.
5. computer simulations are validate
a computer simulation is a program that is run on a computer and that uses step-by-step methods to explore the approximate behavior of a mathematical model.
The algorithm takes as its input a specification of the system's state at some time t. It then calculates the system's state at time t+1. From the values characterizing that second state, it then calculates the system's state at time t+2, and so on. When run on a computer, the algorithm thus produces a numerical picture of the evolution of the system's state, as it is conceptualized in the model.
Computer simulation as a comprehensive method for studying systems. In this broader sense of the term, it refers to an entire process. This process includes choosing a model; finding a way of implementing that model in a form that can be run on a computer; calculating the output of the algorithm; and visualizing and studying the resultant data. The method includes this entire process—used to make inferences about the target system that one tries to model—as well as the procedures used to sanction those inferences
6. Step-Saver Data Systems v. Wyse Technolog
U.S. Court of Appeals for the Third Circuit primarily concerned with the enforceability of box-top licenses and end user license agreements (EULA) and their place in U.S. contract law. During the relevant period, Step-Saver Data Systems was a value-added reseller, combining hardware and software from different vendors to offer a fully functioning computer system to various end users. Step-Saver's products included software produced by Software Link, Inc (TSL), computer terminals produced by Wyse Technology, and main computers produced by IBM. The fundamental question raised in this case was whether the shrinkwrap licenses accompanying TSL's software were legally binding, given that different terms were negotiated over the phone with Step-Saver prior to receiving physical copies of the software.
The case was first heard in the United States District Court for the Eastern District of Pennsylvania, where the court ruled that the shrinkwrap licenses were legally binding. However, the U.S. Court of Appeals for the Third Circuit subsequently reversed this decision, ruling that the shrinkwrap licenses were not legally binding.
Step-Saver's customers filed lawsuits against them. As producers of key components of Step-Saver's overall product, Step-Saver contended that TSL and Wyse were liable in these suits, arguing that the same implied warranties Step-Saver made to its consumers were also made to Step-Saver by TSL and Wyse.
Step-Saver initiated this case in an effort to hold Wyse and TSL liable in their customer lawsuits. Step-Saver argued, that any liability that it had to its customers should be shared by both Wyse and TSL since they were the original providers of the allegedly defective software and hardware. Step-Saver also argued that an implied contract existed between Step-Saver and these merchants at the time of purchase.
Mortenson v. Timberline Software.
Mortenson Company licensed software from defendant Timberline Software Corporation which it used to prepare a construction bid. Due to a "bug" in defendant's software, the bid submitted by Mortenson was $2 million less than Mortenson intended it to be. Mortenson brought suit, seeking to recover consequential damages arising out of an alleged breach of warranty.
The central issue before the court was the terms of the contract between the parties. Mortenson argued that the terms were reflected in a purchase order it had sent to one of Timberline's authorized dealers. Timberline argued that the parties' contract included license terms shipped by Timberline to Mortenson along with the software at issue. As this license contained a clause limiting any claim that could be asserted for consequential damages, Timberline sought to dismiss the suit on a motion for summary judgment.
The license provided that use of the program constituted an agreement to be bound by the terms of the license. If the user did not wish to be so bound, he was permitted to promptly return the program to Timberline in exchange for a refund of the purchase price. The court held that this was a permissible "accept-or-return" license and "that the terms of the present license agreement are part of the contract as formed between the parties.
We find that Mortenson's installation and use of the software manifested its assent to the terms of the license and that it is bound by all terms of that license that are not found to be illegal or unconscionable."
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