The intended outcome of this working group is to derive consensus on modeling strategies for achieving observational data interoperability. To accomplish this goal we will solicit and follow recommendations from a broad community of researchers to develop a core semantic model for scientific observations onto which current and future data models can be mapped. Key to the success of the proposed core semantic model will be outreach to the broader environmental science communities and stakeholders. The goal will be to engage a diverse group of community members to contribute requirements and use cases, and provide feedback on proposed approaches, ultimately leading to ratification of a specification for observational data modeling.