Binding (1)

At a high level, binding is the process of establishing a relationship between nodes that can communicate in a meaningful way - for example, which switches control which lights. It therefore determines the overall functionality of the network.

Binding Mechanism

At a more detailed level, the binding mechanism associates applications which generate information with applications which can use that information.

The information is exchanged as clusters - in order for two applications to be bound, they must have compatible clusters. For example, for two applications on different nodes to be bound for the purpose of temperature control, one must be able to generate an output cluster related to temperature, and the other must be able consume it as an input cluster.

The binding between two applications is specified by:

The source network address and endpoint of the application where the cluster is generated
The destination network address and endpoint of the receiving application
The cluster ID of the cluster being sent between them

Binding Tables

Bindings are stored in a binding table. This lists the cluster IDs, the network addresses and application endpoints for each association. It is possible to generate complex bindings from a single output or input cluster by having multiple entries for the cluster ID in the binding table.

Binding Types

The types of binding that can be achieved are one-to-one, one-to-many and many-to-one:

One-to-one: A binding in which an endpoint is bound to one (and only one) other endpoint
One-to-many: A binding in which a source endpoint is bound to more than one destination endpoint
Many-to-one: A binding in which more than one source endpoint is bound to a single destination endpoint

As an example of these bindings, consider a switch and load controller from the HCL profile.

In the one-to-one case, a single switch controls a single light
In the one-to-many case, a single switch controls several lights, perhaps in the same room
In the many-to-one case, several switches control a single light, such as a light on a staircase, where there are switches at the top and bottom of the stairs, either of which can be used to turn on the light

It is also possible to envisage many-to-many bindings where in the last scenario there are several lights on the staircase, all of which are controlled by either switch.

Click on the light switches in the illustrations below!

One-to-one Binding

One-to-many Binding

Many-to-one Binding

Click "Next Page" to continue.

Quiz