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The PeP Project: Evaluating the Responsiveness of SAP Applications
from a User-Centered Perspective – Appendix
By Gerd Waloszek, SAP User Experience,
SAP AG, and Ulrich Kreichgauer,
oCTO, SAP AG – October 13, 2009
This page offers additional information for the article The
PeP Project: Evaluating the Responsiveness of SAP Applications
from a User-Centered Perspective.
Overview of the Aspects of Human Performance at the Computer
Figure 1 below provides a schematic overview of the aspects of human
performance at the computer, the primary questions that are involved, and how
these aspects are related to technology and UI design:
The Aspects and the Related Questions
- System performance relates to the question: "How fast is
Optimizing system performance includes all involved technical components,
such as the processing, the network, and the visual rendering. Speed is the
motto, here, and we are in a purely technical domain. Increasing speed reduces
waiting times, and it is hoped that with sufficient speed these can be reduced
to practically zero.
- Human performance relates to the question: "How can we improve
human performance through UI design?"
It points to the fact that user interface design plays a critical role for
the performance of human users and attempts to design software applications
in ways that the users' performance is optimized. Here, we are primarily
in the UI design domain, including interaction, information, and visual design,
although technical considerations also have to be considered.
- System responsiveness relates to the question: "How long
do users have to wait at the computer?"
When attempting to improve the system's responsiveness, developers and UI
designers strive to reduce the users' waiting times in spite of the fact
that some system processes – for example, the ones that the users just
had started – have not finished yet. That sounds like a paradox and
you can imagine that some creativity is needed to come up with good solutions
here. The question above sounds as if we were in a purely technical domain,
but this is not the case, as waiting times have an impact on users. Therefore,
this aspect requires close cooperation between technology and UI design,
and thus figure 1 puts it in both fields.
- Perceived performance relates
to the question: "How do users perceive the system's and their performance?"
It indicates that there is often a difference between objective performance
and the subjective impression that it makes on the users. It is not included
in figure 1.
Figure 1: Overview of system performance, system responsiveness,
and human performance and the related questions
This is a more extended version of the time range table presented in the main
article (from Human Performance at the
Computer – Part 2: Making Applications
Acceptable Response Times
Response/Feedback Does Not Appear Timely
|Comments on Untimely Response
||Acknowledge user input
(direct manipulation: key press, mouse click, open/close menu, highlighting,
|Perception of smooth animations and cause-and-effect relationship
||Must not happen!
|Present result of simple tasks
(navigation, open new window), finish unrequested actions (auto-save)
|Engaged user-system dialog breaks down
||Should not happen; provide feedback, allow
user to abort the process
|Present result of common tasks (simple search/calculation)
||User has time to think: the system is perceived as slow,
the user's focus starts to wander, and the user may turn to other
|Present result of complex tasks (complex search/calculation)
||User loses focus on task and may turn to other tasks
||Present result of very complex tasks (extensive search/calculation)
||User gets annoyed; detrimental to productivity and
Table 1: Human time ranges
*) Because these times are only rough guides, most authors simply list the
powers of 10, such as 0.1, 1, and 10 seconds; we have extended the numbers
into consecutive ranges but please do not take the transition points too literally.
The limit of 2 seconds for the dialog level may already be too high.
**) We took the terms "simple," "common," and "complex" tasks
directly from the literature. In our opinion, they are only of limited use
because they do not clearly describe the task types at the respective levels.
The following graphic offers a graphical overview of human time ranges and
the corresponding tasks and user reactions:
Figure 1: Graphical description of human time ranges (click image for
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