In component-based simulation, models developed in different locations and for specific purposes can be selected and assembled in various combinations to meet diverse user requirements. This paper proposes CODES (COmposable Discrete-Event scalable Simulation), an approach to component-based modeling and simulation that supports model reuse across multiple application domains. A simulation component is viewed by the modeller as a black box with an in- and/or out-channel. The attributes and behavior of the component abstracted as a meta-component are described using COML (COmponent Markup Language), a markup language we propose for representing simulation components. The integrated approach, supported by a proposed COSMO (COmponent-oriented Simulation and Modeling Ontology) ontology, consists of four main steps. Component discovery returns a set of syntactically valid model components. Syntactic composability is determined by our proposed EBNF syntactic composition rules. Validation of semantic composability is performed using our proposed data and behavior alignment algorithms. The semantically valid simulation component is subsequently stored in a model repository for reuse. As proof of concept, we discuss a prototype implementation of the CODES frameworkusing queueing system as an application domain example.