In the ITEA2 Do-It-Yourself Smart Experiences project (DIY-SE), we are required to design an ontology-based ambient computing environment to support users to DIY their personalized solutions. In this paper, we illustrate how to manage data semantics using Semantic Decision Table (SDT). We use a simple rule writing language called Decision Commitment Language (DECOL) to store the SDT commitments. Semantic Decision Rule Language (SDRule-L), which is an extension to Object Role Modelling (ORM), is used to graphically represent DECOL. In this paper, we will demonstrate how SDT, together with SDRule-L and DECOL, are used by both technical and non-technical end users.