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Components

Components are at the core of ESL specifications. Typically, your (to be developed) systems will live as a component within the world. Components are introduced using a definition such that they can be instantiated in the world.

We are going to specify a water pump, that consists of a centrifugal pump driven by an electromotor, with several requirements to the subcomponents, dimensions, and performance.

So in our case, the world becomes:

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world
  components
    pump is a CentrifugalPump
    drive-mechanism is an ElectricalDriveMechanism


define component CentrifugalPump
  empty


define component ElectricalDriveMechanism
  empty

Where each component definition is defined using the define component keyword combination followed by the component [name], which cannot have any spaces. Dashes are fine.

Within the world definition, we instantiate defined components by given them a local name and referring to their definition with [name] is a [defined component].

Note

Note the difference between definition and instantiation. Definitions are similar to classes or templates in other programming languages and instantiations are similar to the actual instances or objects.

Tip

It is recommended to use a CamelCase notation for definition names and to use a lower-case notation with dashes for instantiation names.

Tip

We can refer to the defined components before their written definitions. The ESL compiler is smart that way and resolves later define component [name] statements by default.

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