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5.3. The Artifact-Based Approach
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Accordingly, history of data is maintained in the same nature as the real-
world events have happened: this also allows fusion of data across artifacts
on the higher setting-layer, if the semantic of di erent artifacts is known, e.g.
meaning of co-location of specific objects.
In general, the output of the artifact layer is abstracted sensor data related to a
physical artifact. This can include symbolic or sub-symbolic data representing the
context. Additionally there is also access to a history of collected data.
Setting Layer
In the setting layer we look at a tightly grouped set of artifacts or devices that
are cooperating. The cooperation between them is for the purpose of supporting
a particular setting. On a conceptual level a setting presents a local collective
perception system that consists of a number of networked artifacts with perception
capabilities. The following questions help to establish the facts about the settings:
What is the relationship among artifacts?
What is the purpose of the setting?
Who are the users?
What perception primitives are provided?
As the perception is distributed and collective, it is interesting to establish how
the perception primitives within the setting are related. Of special interest is the
question if the same perception primitive in di erent artifacts within one setting is
observing the same phenomenon from di erent angles or if the report is on di erent
observations. This is a non-trivial problem, similar to the registration problem in
computer vision.
When looking at artifacts that o er perception and can take part in collective per-
ception systems (settings) at a larger scale, it is important to discriminate between
artifacts that are exclusively part of one setting and artifacts that are part of mul-
tiple settings. In the latter case conflicting interests between settings can lead to
a resource sharing problem (similar to operating systems). This can be resolved
by negotiating capabilities between the setting requesting and the artifact o ering
perception.
On a technical level, how the devices are connected and how communication is
realized becomes important. In the straightforward case, a pre-defined group of
artifacts (defined at implementation time) is permanently connected. However in
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