35 lines
2.0 KiB
Markdown
35 lines
2.0 KiB
Markdown
---
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layout: documentation
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---
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{% include base.html %}
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# Concepts
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Eclipse SmartHome strictly differentiates between the physical view and the functional view on the system.
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While the physical view is required for setup, configuration, troubleshooting, etc., the functional side covers the information that matter to applications, such as user interfaces and automation logic.
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## Things, Channels, Items and Links
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**Things** are the entities that can be physically added to a system and which can potentially provide many functionalities at once. It is important to note that things do not have to be devices, but they can also represent a web service or any other manageable source of information and functionality.
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Things provide their functionality through a set of **Channels**. Channels are "passive" and can be regarded as a declaration of a Thing, what it can offer. It is up to the individual setup, which of the Channels are actively used through Items (see below).
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**Items** represent (fine-grained) functionality that is used by applications - as user interfaces or automation logic. Items have a state and they can receive commands.
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The glue between Things and Items are **Links**. Links are associations between exactly one Thing Channel and one Item.
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If a Channel is linked to an Item, it is "enabled", which means that the functionality that the Item represents is handled through the given Channel.
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Channels can be linked to multiple Items and Items can be linked to multiple Channels.
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To illustrate these concepts, take a two-channel actuator that controls two lights:
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The actuator is the _Thing_. This might be installed in the electrical cabinet, it has a physical address and needs to be setup and configured in order to be used.
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The user is instead interested in the two lights, which are located at different locations in his home. These lights are the desired functionality, thus the _Items_ and they are linked to the _Channels_ of the actuator.
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A _Link_ can be regarded like a physical wire in this example.
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