In event driven architectures following RMS patterns you have a few different ways of handling incoming events – we can think of four different patterns, three of them supported in QuantLET:

Specialized Declarative

Mostly through a declarative language (CEP guys/gals love that) like EQL or dialects. In other words, a language specialized for event handling (DSL). But be advised – despite of its ‘coolness’ and being (most times at least) a time saver and a shortcut it requires specialized skills and tools not available on every corner (translation: lots of $$$).

Functional Declarative

Similar to above, one example would be something like a lisp-like dialect. Another example are constructs based on paradigms like map-reduction for large data fabric clusters. All as above applies

Second-Order Declarative

Based on inferences derived from second-order logic descriptions. You: “What? Why are you bringing this up here?” Me: Well, inference engines, specially RETE engines, are basically a correlated forwarded-chain of rules and facts, optimized in a tree-like fashion for speed in which “triggering” can be seen as an event’s action.

A time saver, flexible, and ideal when proper tools and resources are not available.

Finite State Machines

Actions are associated to changes in state represented by a directed graph. Conditional transitions are also supported by ‘guards’. Incoming events carry either a next state of the graph, or the indication of a transition. Different types of actions are then performed based on the transition and the association, i.e: actions performed when entering a state (entry), leaving a state (exit), or when changed from one specific state to another (transition).

Observer-Observable Imperative

Simplest, but can lead to a lot of code to write that *will* turn into spaghetti if done by the uninitiated. Base yourself on proven paradigms that enforce separation of control and state to avoid adding to your own pain.

Procedural Imperative

Read ‘anything-else-imperative-except-the-observer-pattern-mentioned-above’ – Don’t even think about trying that unless your model is *really* simple…

Ok — Now, pick one, any one…