## 2 Methodology for Defining a Workflow
### Characterization of the Information of the Renovation Process  
The main objective of the characterization of the information is to set a commonly understood reference framework of the renovation process as it is, to consider the classification in the definition of workflows and the definition of use cases. Particularly, a taxonomy of the renovation process in terms of typologies, stakeholders, and phases was defined, which will pave the way for defining the overall workflow in renovation in a standard way. To characterize the type of renovation intervention proposed, some authors have considered the different technologies to be adopted [51; 52] while others focus on the final target of the intervention [53]. A combination of both the technology together with the specific result pursued after the intervention can also be considered [54; 55]. In the BIM4 Ren project, a categorization of renovation typologies was carried out that was further deepened through the elicitations gathered from the stakeholders participating in the Living Labs [42]. The standardization of the typologies, as well as the type of stakeholders involved and the tasks performed in each one, enabled the systematization of workflows. The typologies cover a range of factors, from the single works prior to renovation, such as maintenance and inspection, to more complex processes, such as deep renovation. In this article, to exemplify the definition of workflows, the typology identified as \"renovation in the envelope\" was selected to be addressed. On the other hand, considering the difficulties for cooperation in such a complex environment, it is becoming essential to automate the workflow with an appropriate identification of phases and activities, where the interrelations are well defined. Although many efforts have been conducted for the characterization of the construction phases according to several standards (UNIClass2, OMNIClass, PAS 1192) [56; 57; 58] and renowned associations, such as, RIBA [59], AIA [60], NATSPEC [61], CIC [62], etc., there is no agreed-upon standardization of the renovation phases. The renovation characterization must take into consideration the singularities of the renovation, which are mainly focused on the interaction of the works with the existing building and the involvement of the tenants, whose activity must be made compatible with the refurbishment works. On the basis of one of the most common classifications, i.e., the RIBA plan of work [59] for construction stages, the phases of a renovation process were set as follows, considering the particular approach of the retrofitting [63; 64]:  
1. Strategic definition. 2. Information gathering and survey. 3. Diagnosis. Figure 1: Methodology concept. Main components involved (**left**) and application sequence (**right**). Renovation conceptual design. * 5. Renovation technical project. * 6. Construction. * 7. Handover and close out. * 8. In use. Phases such as \"information gathering and survey\" and \"diagnosis\", which are the cornerstones of the renovation, were added to the standard classification. The first one is devoted to collecting information about the existing building such as geometry, materials, elements, constructive sections, pathologies, etc. It involves surveys and visual inspections, destructive or non-destructive techniques for the characterization of elements and/or materials, as well as technologies for data capture such as photogrammetry or 3D scanners. The second one consists of the assessment of key parameters of the existing building to set the most suitable solution for retrofitting according to the customer's requirements and the state of the building. The analysis of the stakeholders in a construction process is not the target of this paper, but rather to harmonize them in a framework with the common types of stakeholders involved in a renovation process.