The work of the state has been transformed by digitalisation and datafication, with paper systems increasingly complemented and replaced by digital data systems. While much research has been undertaken on the effects of these data systems on e-government and e-governance, relatively little critical attention has been paid to the ontological nature of the data systems themselves, how they come into being, operate, iterate, and work in conjunction with other systems. In this paper, we build on work that understands the nature of data systems as data assemblages; that is, as being thoroughly socio-technical in nature, emerging and unfolding contingently, contextual and relationally through material and discursive practices and processes. We extend Kitchin (2014) and Kitchin and Lauriault’s (2018) notion of a data assemblage through an engagement with assemblage theory, and detail how data systems are articulated and scaffolded into being, and scaled into a functioning data ecosystem, which is conceptualised as an assemblage of data assemblages. We illustrate the utility of this reconceptualization through an analysis of the development and control function of the Irish planning system, which is composed of a number of interlinked data systems used for managing the entire planning process from seeking planning permission, monitoring construction, to completed property.