SAPERE Incarnation

The SAPERE incarnation for Alchemist was the first stable incarnation produced for the simulator. It was developed in the context of the SAPERE EU project.

At the core of SAPERE is the concept of Live Semantic Annotation (LSA), namely a description of a resource (sensor, service, actuator…) always mapping the current resource status (somewhat a prelude to the currently famous digital twin concept).

These annotations evolve following so-called Eco-Laws, mimicking the complex behaviours of natural ecosystems.

The SAPERE approach fostered subsequent approaches, such as aggregate computing.

Live Semantic Annotations

An LSA as modeled in Alchemist is a tuple of values. These tuples can be injected in nodes as data items. From the point of view of the Alchemist metamodel, the concept of Molecule is mapped to LSA (LsaMolecule). As a consequence, LSAs can be inserted in nodes.

Eco-Laws

Tuple matching is used to define Eco-Laws. An Eco-Law is a rewriting rule very similar in concept to chemical reactions: elements on the left-hand side of the reaction are removed from the container, elements on the right-hand side are inserted instead.

The following program matches LSAs with two arguments, the former must be foo, the latter a number greater than 30, and produces in a new tuple having as first element bar and as second the opposite of the matched number:

{ foo, def: N > 30 } --> { bar, -N }