ion axis Concepts/ ontology axis Experiments/ documentation/ evidence axis Figure 3.12 Abstraction, evidence, and concepts coordinates. cept can have several experimental results or evidences related to it. For example, we may define five different levels (molecule, cell, tissue, organ, and system) for human anatomical data, and each data source can be classified into a certain level. Figure 3.13 demonstrates the data source integrations from the horizontal and vertical approaches. The horizontal approach integrates data sources at the same abstraction level. In contrast, the vertical approach integrates data sources from different abstraction levels. In order to integrate data in different abstraction levels, we need to establish connections/interactions between them. It will be necessary to propose some biological relationships that can describe the relationships and interactions between data at the different levels as building blocks of vertical data integration.