Commit 61fa30d37740a434e8de1b48f6e9a40903e97443

Authored by Geoffrey Challen
1 parent 5b8d931f

Mine.

Showing 1 changed file with 26 additions and 49 deletions
usage.tex
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2 2 \label{sec-usage}
3 3  
4 4 To motivate the need for a value measure, we return to the questions posed in
5   -the introduction. We explore each in more depth, providing a more detailed
6   -description of how a value measure could be used. These use cases also help
7   -us develop requirements for our metric, which are summarized at the end of
8   -this section. We begin by exploring the basic question at the heart of the
9   -problem: what is the value delivered by an app?
  5 +the introduction and explore each in more depth. These use cases also help us
  6 +develop requirements for our measure, which are summarized at the end of this
  7 +section. We begin by exploring the basic question at the heart of the
  8 +problem: what is the value of an app?
10 9  
11   -\subsection{What is Value?}
12   -
13   -\begin{comment}
14   -
15   -\begin{quote}
16   -I shall not today attempt further to define the kinds of material I
17   -understand to be embraced within that shorthand description; and perhaps I
18   -could never succeed in intelligibly doing so. But I know it when I see it,
19   -and the motion picture involved in this case is not that.\\
20   ----Justice Potter Stewart~\cite{jacobellisvohio}.
21   -\end{quote}
22   -
23   -\end{comment}
  10 +\subsection{What is App Value?}
24 11  
25 12 All smartphone users intuitively realize that smartphone apps differ in
26 13 value---an email client, for example, is probably more valuable than a app
27   -that makes farting sounds, and a chat client is probably more valuable than a
28   -chat client that only sends the message ``yo''. In Supreme Court Justice
29   -Potter Steward's famous formulation, they know value when they see it. But is
30   -it possible to quantify these subjective distinctions and produce a value
31   -measure?
  14 +that makes farting sounds. But is it possible to quantify these subjective
  15 +distinctions and produce a value measure?
32 16  
33 17 To argue that this is possible we present two experiments that elucidate
34 18 smartphone app value in the form of both ordinal and cardinal utilities,
... ... @@ -49,19 +33,15 @@ battery percentages to each app you use.
49 33 %
50 34 We plan to engage smartphone users in studies to explore in more detail which
51 35 of these approaches is more effective, comparing them by comparing users'
52   -levels of satisfaction under each scenario. As an alternate formulation of
53   -the second experiment to make it more similar to the first, the adversary
54   -could remove the apps consuming the least energy up to a given target.
55   -
56   -For our value measure we are hopeful that users will prove capable of
57   -assigning cardinal utilities to apps---as in the second experiment---since
58   -this matches most directly with our proposed value measure and could provide
59   -ground truth for a value measure computed automatically. The second
60   -experiment also engages users directly in the task of allocating energy,
61   -which is one way that a value measure could be used. However, if ordinal
62   -utilities prove more intuitive we can still compare the ordering generated by
63   -our value metric with the ordering generated by users, although the specific
64   -values of the measure will still require justification.
  36 +levels of satisfaction under each scenario. For our value measure we are
  37 +hopeful that users will prove capable of assigning cardinal utilities to
  38 +apps---as in the second experiment---since this matches most directly with
  39 +our proposed value measure and could provide ground truth for a value measure
  40 +computed automatically. The second experiment also engages users directly in
  41 +the task of allocating energy, which is one way that a value measure could be
  42 +used. However, if ordinal utilities prove more intuitive we can still compare
  43 +the ordering generated by our measure with the ordering generated by users,
  44 +although the values of the measure will still require justification.
65 45  
66 46 In either case, we believe that these experiments do suggest the existence of
67 47 quantifiable value for smartphone apps. We are not claiming, however, that
... ... @@ -90,15 +70,14 @@ consumption. Unless it is terribly written, the chat client will consume less
90 70 energy. But this does not mean that it is efficient, or that the
91 71 videoconferencing app is not. Ultimately, all the energy consumption
92 72 comparison truly reveals is that the two apps do different things---which we
93   -knew.
  73 +already knew.
94 74  
95 75 Using energy consumption alone even makes apples-to-apples of the same app
96 76 difficult. Given an app that consumes twice as much energy on Alice's
97 77 smartphone than on Bob's, the question of why is left unanswered by pure
98 78 energy measures. Even if usage time can be used to normalize the comparison
99 79 to the power consumed, power consumption alone cannot incorporate differences
100   -due to the different app features used by Alice and Bob or the different ways
101   -that they have configured the app.
  80 +due to the different app features or configurations used by Alice and Bob.
102 81  
103 82 By computing value and, thus, energy efficiency, we can overcome these
104 83 weaknesses. A value measure should allow us to compare the efficiency of two
... ... @@ -108,10 +87,10 @@ video players. Comparisons within the same app category should allow users to
108 87 select the most efficient email client or web browser. Aggregating results
109 88 over all users, differences in app energy efficiency should reflect how well
110 89 the app is written and how well it predicts and adapts to users, not just
111   -differences in the core features it provides. And when comparing two users
112   -using the same app, differences in energy efficiency should reflect different
113   -configurations or differences in how efficiently at app provides certain
114   -features, not just that one user is using one feature and another is not.
  90 +differences in the core features it provides. When comparing two users using
  91 +the same app, differences in efficiency should reflect different
  92 +configurations or differences in how efficiently the app provides certain
  93 +features.
115 94  
116 95 \subsection{Evaluating App Changes}
117 96  
... ... @@ -150,9 +129,9 @@ allocates a rate to each app and enforces that rate by slowing or stopping
150 129 the app when it exceeds its
151 130 allocation~\cite{odyssey-osr99,cinder-eurosys11,Zeng:2003,pixie-sensys08}.
152 131 However, all of these previous efforts have ignored the critical question of
153   -\textbf{how rates should be set}. No matter how effective the enforcement
154   -mechanisms are, systems that rely on rates will fail if they provide the same
155   -rate to Skype and Snapchat, or to a very efficient app and an energy virus.
  132 +how rates should be set. No matter how effective the enforcement mechanisms
  133 +are, systems that rely on rates will fail if they provide the same rate to
  134 +Skype and Snapchat, or to a very efficient app and an energy virus.
156 135  
157 136 A measure of value can be used alone or in conjunction with energy consumption
158 137 to help prioritize limited energy resources. The simplest approach is to
... ... @@ -186,10 +165,8 @@ inputs, requiring that it be calculable given data from a single user.
186 165 app generate value and what parts do not.
187 166  
188 167 \item It should be able to be efficiently computed to not overly consume the
189   -very resource that it is designed to help manage.
  168 +resources that it is designed to help manage.
190 169  
191 170 \item It should be derived with little to no input from the user.
192 171  
193 172 \end{itemize}
194   -%
195   -We continue by discussing possible inputs to such a metric.
... ...