  Life, services and activities within cities have commonly been studied by
separate disciplines, each one independent from the others. One such approach
is the computer simulation, which enables in-depth modelling and cost-effective
evaluation of city phenomena. However, the adoption of integrated city
simulations faces several barriers, such as managerial, social, and technical,
despite its potential to support city planning and policymaking. This paper
introduces the City Physiology: a new conceptual framework to facilitate the
integration of city layers when designing holistic simulators. The physiology
is introduced and applied through a process of three steps. Firstly, a
literature review is offered in order to study the terminology and the progress
already made towards integrated modelling of different urban systems. Secondly,
interactions between urban systems are extracted from the approaches studied
before. Finally, the pipeline to carry out the integration strategy is
described. In addition to providing a conceptual tool for holistic simulations,
the framework enables the discovery of new research lines generated by
previously unseen connections between city layers. Being an open framework,
available to all researchers to use and broaden, the authors of this paper
envisage that it will be a valuable resource in establishing an exact science
of cities.
