  The paper investigates the relative expressiveness of two logic-based
languages for reasoning over streams, namely LARS Programs -- the language of
the Logic-based framework for Analytic Reasoning over Streams called LARS --
and LDSR -- the language of the recent extension of the I-DLV system for stream
reasoning called I-DLV-sr. Although these two languages build over Datalog,
they do differ both in syntax and semantics. To reconcile their expressive
capabilities for stream reasoning, we define a comparison framework that allows
us to show that, without any restrictions, the two languages are incomparable
and to identify fragments of each language that can be expressed via the other
one.
