Algebraic observability of linear differential–algebraic systems with delay

The paper deals with the problem of algebraic observability for linear differential-algebraic systems with delay. For such systems, we present the observability matrix. By algebraic properties of the matrix we define some concepts of observability. We give necessary and sufficient conditions of these algebraic observabilities. We prove relations between these types of observabilities along with spectral observability. Practical verifiability of the conditions is demonstrated on several examples.