This paper presents a formalism for representing and reasoning about Web services with local closed world assumption (LCWA) on the basis of $\mathcal{ALCO@K}$. In our formalism, the knowledge about the states of the world is encoded in $\mathcal {ALCO@}$-ABoxes; atomic services are represented in terms of their preconditions (epistemic queries to the knowledge base) and effects (possibly negated $\mathcal{ALCO@}$-assertions involving only atomic concepts); and composite services are built up with action constructors in dynamic logics. We also summarize some reasoning tasks and develop a calculus for them. Our formalism also enjoys \emph{introspection}. The main features of our proposal (i.e., dynamic reasoning, local closed world assumption and introspection) make it more philosophically satisfying and much closer towards a practical formalism for agents with incomplete knowledge in the Web full of static information and dynamic processing.