BioMaterial is an abstraction of various states of biology-based materials used in various stages of the microarray experiment. Biosource refers to the initial source of material used in hybridization (e.g., cell line or tissue). Biosample is what is extracted from the biosource, and labeled extract is the last state of the biomaterial before hybridization. A biomaterial can be a result of a chain of treatments, each treatment involving one or more biomaterials in some amounts. A special kind of treatment is treatment with some amount of a compound. A simple way to model compounds consisting of other compounds is provided.