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%Assignment is conducted in pairs. Max. 8 pages. |
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\documentclass[12pt, a4paper]{article} |
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\usepackage[latin1]{inputenc} |
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|
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\begin{document} |
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\pagenumbering{roman} |
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\thispagestyle{empty} |
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\begin{centering} |
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Assignment 1 - PAC003: Software Metrics, 5p\\ |
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Jonas Petersson \& Mathias Börjeson\\ |
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\emph{jopd01@student.bth.se \& tb00mbo@student.bth.se}\\ |
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\end{centering} |
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\tableofcontents |
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\newpage |
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\pagenumbering{arabic} |
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\section{Internal product attributes} |
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\subsection{Explain how the three aspects of the software size (Length, |
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Functionality and Complexity) are supplementing each other to describe |
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the notion of software size.} |
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%length = is a physical size of the product |
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%functionality = counts the functions supplied by the product |
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%complexity = measures the complexity od underlying problem, or a solution |
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%utan att ha en aning om hur notationen ser ut drar jag till med följande |
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These three supplements each other adding references to |
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each other. None of these is useful by itself, but by |
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adding them up one can get a better perspective of the |
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size of the software. The length itself don't tell |
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anything of how large the completed software will be, but |
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together with functions and complexity one can understand |
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the size of the software. Once the size of the software is |
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established one may come with effort estimations, and |
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based on those make a budget for what resources the |
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project will need. Given these three it is possible to get |
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an idea of how productive a programmer is during a time |
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unit. It will not be a perfect answer, but it will be |
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something that could be used to measure deviations in work |
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etc. |
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\subsection{Give an example where code length measure can be useful and an |
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example where source code length measure is not useful.} |
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Code length is useful if it is not going to be used by |
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itself. One example of this could be if we are interested |
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in how much work is done in a week. Then we could look at |
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loc, and also take into account the complexity and the functions provided |
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(like loc * complexity / functions or something similar). |
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Then loc could be useful. |
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|
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Code length is useless if it is used by itself. For |
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example the statement I am a good programmer since I |
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produce more then n loc per week useless. |
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\subsection{Explain what are the main ideas behind Albrecht's Function Points. |
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Discuss advantages and disadvantages of the measure. Motivate.} |
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%denna var bra http://www.spr.com/products/function.htm |
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The main idea behind FP's are to provide language |
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independent metric that can be used no matter what |
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language are used. Albrech thought it was wrong that the |
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only way to tell effort and cost per effort until he begun |
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was in loc. A often used metric to tell productivity was |
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cost/loc, and that don't tell anything since different |
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languages require different number of loc's to solve the |
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same problem. This cost could be lover if the language |
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requires a lot of code, but the end cost could still get |
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higher if the program takes longer time to complete. |
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The main idea behind FP's is to give ways to |
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tell cost and productivity in a way that is language |
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independent. FP's does satisfy this idea. A easier |
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language will get a lower cost/FP and a greater number of |
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FP's/person\&month then a more complex language. |
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|
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The great advantage with this method is that it is (almost) truly |
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language independent, while a disadvantage would be that |
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if this is established in the beginning of a project and |
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should be used to choose a appropriate language to use, if |
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the language is unfamiliar, then these metrics can't be |
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computed (like FP's/person\&month). Also this way of presenting |
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the result does not take into account training and |
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inexperience while showing the result. Also this should |
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not be used to compare different projects or groups to se |
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the difference between them since this does not take |
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everything into account. Also one might be tempted to |
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always use the language with the highest productivity, |
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this is good in most cases, but sometimes there are other |
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factors to sum in, like speed, security etc. |
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\subsection{Describe structural measures presented by Fenton. (Control flow |
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structure, Data flow structure, Data structure). Give an example |
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where you explain how one could use the structural measures |
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(specify which structural measure) to ensure the quality of the |
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software product.} |
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%http://sern.ucalgary.ca/~kliewerc/SENG/623/summaries.htm#sum02 var lite halvbra... det bästa jag kunde hitta dock, + F4... |
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Control flow is a diagram with nodes, connected via the |
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directed connections showing the possible routs the |
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program (or actually the flow of data in the program) may |
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take. This could be broken down to several diagrams if it |
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gets to large and complex. This diagram can be used to |
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decide how many test cases is needed to test the program |
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completely. |
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|
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The data flow structure could be shown in a module-call |
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graph. The module-call graph shows what modules calls what |
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other modules, and thereby showing more the flow of |
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information within the program. This may also be used to |
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show coupling and cohesion in the program. |
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|
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The data structure can be measured both locally and |
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globally. Locally it is interesting how much data |
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structure each data item has, and globally it is the |
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amount of data for the system. For the local data |
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structures very little research has been done, but for the |
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global there are more. |
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\subsection{Draw the flow graph for the program, which |
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based on the data provided by everyday measurements of the air |
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temperature will calculate the maximum, minimum and the most |
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commonly occurred temperature (the temperature that occurs twice |
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or more) for a given month. Present program paths that has to be |
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executed in order to satisfy the following testing strategies:} |
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See appendix a for the diagram. |
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\subsubsection{Statement coverage} |
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a-b-c-d-e-f-g-h-i-j-k-l-m-n |
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\subsubsection{Branch coverage} |
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a-b-c-d-e-f-g-h-i-j-k-l-m-n \\ |
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a-b-c-b-c-d-e-g-i-j-k-m-n \\ |
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a-b-c-d-e-f-g-h-i-j-k-l-m-k-m-n \\ |
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\subsubsection{Visit each loop} |
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%osäker på om detta är rätt...jag har bara antagit att man skall göra ett test så att man kör alla looparna |
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a-b-c-b-c-d-e-f-g-e-f-g-h-i-g-h-i-j-k-l-m-k-m-n |
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\subsection{Calculate the cyclomatic complexity of your program. What does |
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this figure tell you?} |
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%Cyclomatic complexity (CC) = E - N + p |
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%where E = the number of edges of the graph |
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%N = the number of nodes of the graph |
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%p = the number of connected components |
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%http://www.sei.cmu.edu/str/descriptions/cyclomatic.html |
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Hopefully you mean McCabe's cyclomatic complexity\\ |
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% e = no of arcs | n = no of nodes |
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e-n+2 | 18 - 14 + 2 = 18 - 16 = 2 \\ %men vad säger nu detta |
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This tells us the number of tests we have to do to cover |
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each path in the program. It could also be used to give a |
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estimation of how complex the final software will be. If |
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higher then 20 it should be seen as a high risk project, |
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and if higher then 50 as a very high risk project. %nuffrorna kommer från http://www.sei.cmu.edu/str/descriptions/cyclomatic.html |
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\section{OO metrics} |
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\textbf{Measuring the use cases} |
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%vi skall använda templaten, och bifoga denna... |
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\subsection{Measure the use case specifications shown in Design 1 using the |
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chosen use case metrics suite from the lecture} |
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See appendix b. |
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\subsection{Measure the use case specifications shown in Design 2 using the |
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chosen use case metrics suite from the lecture} |
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See appendix c. |
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\subsection{Write a short section (up to ½ page) with answers to the following |
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questions:} |
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\begin{itemize} |
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\item Which of the two systems presented can be expected to be |
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more complex and why? |
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\item Which of the two systems can be expected to require more |
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effort to be built? Why? |
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\end{itemize} |
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We expect design 2 to become more complex, both since |
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it has more use cases, but also since it has higher |
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values (in general) on the metrics suit. |
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|
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We expect design 2 to require more effort to build |
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since it has more use cases and more actions (more |
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functionality). Also since we feel that design 2 has a |
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higher complexity. Also most of the values that we can |
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get out from our metrics suit are greater, both in |
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total and if we count them per use case. |
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|
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We feel that it is hard to make good (accurate) |
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estimations based on this suit only and we also feel |
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that while good estimations on use case level can be |
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made using this suit, it is not a good thing to try to |
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make estimations of the system as a whole only based |
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on this information. |
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\\ \\ \textbf{Measuring designs} |
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\subsection{Measure the class diagram presented in Design 1 using the CK metrics suite presented on the |
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lecture.} |
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See appendix b. |
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\subsection{Measure the class diagram presented in Design 2 using |
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the CK metrics suite presented on the lecture.} |
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See appendix c. |
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\subsection{Measure the code in the files .java from Design 1 with the CK metrics suite |
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presented on the lecture.} |
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See appendix b. |
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\subsection{ Measure the code in the files .java |
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from Design 2 with the CK metrics suite presented on the lecture.} |
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See appendix c. |
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\subsection{Write a short section (up to ½ page) with answers to the following |
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questions:} |
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\begin{itemize} |
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\item Which of the metrics could not be computed based on the class |
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diagrams? Why? |
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\item Which of the two systems is more complex? Why? |
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\end{itemize} |
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Svar |
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\subsubsection{Which method of gathering metrics - from UML designs or source |
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code - is less time consuming?} |
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svar |
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\section{External product attributes} |
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\subsection{Describe how the external product attributes differ from the |
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internal ones. Describe the connection between external and |
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internal product attributes.} |
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The internal attributes can be measured from within the |
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system (like loc etc) while for the external attributes |
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one must look at the finished product to se the external |
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attributes. Also in general internal attributes are |
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considered easier to measure (and then predict) then the |
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external attributes. |
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|
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This is partly since the internal attributes can be |
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measured more ``directly'' then the external. For |
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instance loc is easy to count while usability is a lot |
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harder to measure. For the internal attributes one can |
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expect to be able to get absolute values while on the |
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external attributes one can expect them to be less |
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accurate. |
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|
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However several of the internal attributes (if not all) |
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does affect the external attributes in a way that can |
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(in most cases) be predicted. One can for instance say |
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that in a specific solution if the loc is increased |
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(both with comments) then one could expect to get a |
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higher maintainability. Also most of the external |
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attributes can be affected via the internal if the |
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developers keep the external attributes in mind. |
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|
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In most cases (if not always) the customer of the product |
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is more interested in the external attributes. Does this |
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mean that the external attributes are of ``greater'' |
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value to the team developing the product? |
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|
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Not always but in many cases. Also one should keep in |
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mind that just because the external attributes are more |
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important that the internal could be forgotten. |
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%\subsection{Assume that you are working at the company that |
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%mainly specializes on developing of web-based applications. |
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%Your manager gives you an assignment to develop a software |
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%quality model for the company. The model should show external |
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%quality attributes, corresponding internal attributes and |
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%metrics. Present the assumptions that you will use while |
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%creating of the quality model. Provide an explanatory text |
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%for your model.} %Jag tyckte inte om att läsa den texten;) |
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\subsection{Assume that you are working at a company that |
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mainly specializes in development of web-based applications. |
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Your manager gives you an assignment to develop a software |
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quality model for the company. The model should show external |
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quality attributes, corresponding internal attributes and |
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metrics. Present the assumptions that you will use while |
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creating the quality model. Provide an explanatory text |
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for your model.} |
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Assumptions: We are using an iterative development |
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process, we are using function points to measure progress, |
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we are using a good configuration management tool, we are |
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identifying risks before starting a project, we are, but |
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not always using uml for our projects. |
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|
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Since we are working on web-based applications we also |
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assumed that we are selling those to a customer. This made |
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us make a value based quality view. This made us decide |
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that usability, lernability, reusability, maintainability, reliability, |
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is the most important external attributes. The internal |
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attributes are not considered as important, other than to |
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help up the external. Customer satisfaction does supersede |
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this thou. The external attributes has the following |
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impact on customer satisfaction: \\ |
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\begin{tabular}{|l|l|l|} |
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\hline |
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Attribute & Importance & Role \\ \hline |
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Usability & High & |
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Decides if the customer fells that he may use\\ |
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& & the product or not. The more usable the product\\ |
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& & becomes, the higher value it gets (and thereby\\ |
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& & higher quality). \\ \hline |
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%hmmm, borde finnas nått bättre sätt... |
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Learnability & High & |
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The quicker the end-user can learn to use the \\ |
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& & program, the quicker he feels the value of the\\ |
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& & program and does need it. This makes the \\ |
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& & customer feels a gain from buying our product \\ \hline |
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Reusability & Medium & |
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This is only important if using agreements like\\ |
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& & ``avtal 90'' or similar that gives us the freedom\\ |
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& & of the developed artifacts, and may use them in\\ |
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& & projects to come. If the customer has no demands\\ |
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& & on this, and will own the artifacts then it is \\ |
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& & not taken into consideration.\\ \hline |
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Maintainability & Medium & |
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This is only important if we are using the \\ |
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& to low & |
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reusability from above. And only to support that\\ |
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& & purpose. Otherwise this would not have been a \\ |
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& & issue at all. \\ \hline |
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Reliability & High & |
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This is important since a reliable program is \\ |
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& & seen as having a higher value. \\ \hline |
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\end{tabular} \\ \\ |
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Internal attributes are only important in order to gain |
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the external attributes. |
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\end{document} |
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