Mubtadaʾ: the element about which something is said.
Khabar: the element by which the assertion is completed.
Default: definite topic, indefinite predicate; an indefinite topic may occur with meaningful licensing (qualification, question, negation, fronting, supplication).
Definite + indefinite: normally the definite is the topic, the indefinite the predicate.
Both definite: examine the intended predication and context.
In every parsing exercise state the role, case, and reason.