## 3 Data and Method
### Workflow of the Developed Methodology
#### 3.2.3 Project and Management Planning
Figure 5 presents the information requirements hierarchy for a BIM-enabled project. According to the recommendations presented in references [18; 21], it is essential that the appointing party (e.g., the customer) understands exactly what asset and/or project-related information is required to achieve organisational and project objectives. Information requirements can come from both within the organisation and from external project stakeholders involved in the development, operation, and maintenance of the asset. The appointing party must be able to clearly communicate these requirements to all project stakeholders. It is important to mention that these principles apply in a proportionate manner (i.e., only provide the necessary information, at the required level of detail, to actors actively using the information). Additionally, appointed parties (i.e., general contractor and subcontractors) may introduce information requirements in addition to those defined by the employing party. Existing Conditions Modelling (ECM) [22] is one of 50 specific Building Information Modelling (BIM) use cases defined by buildingSMART [23] with the goal of exchanging experiences from already implemented or ongoing BIM projects among experts. It refers to the development of a digital model that represents the existing conditions of a built asset and involves precise modelling and documentation of the current state of a building or infrastructure, prior to any intervention. The ECM case is very important for efficient planning and to avoid problems during project implementation. The resulting digital model provides a detailed reference for all parties involved in the project (customer, designer, contractor, etc.) and allows them to make informed decisions based on accurate field data. Figure 6 presents the information requirements definition for a BIM-enabled ECM project. Figure 5: Information development process for a BIM-enabled project. Figure 6: Information development process for a BIM-enabled ECM project. The model development according to the requirements of the ECM use case includes three steps:  
* In the first stage, data collection is achieved through technologies such as 3D laser scanning (TLS) and/or photogrammetry, where data about the conditions of the physical asset are collected. The result is an accurate digital representation that includes the structural elements, installations, finishes and other relevant characteristics of the asset in accordance with the defined requirements; for collecting data related to elements that are not visible (e.g., underground installations), GPR (Ground Penetration Radar) can be used. * In the second stage, field data are consolidated and used to create a detailed BIM model (at the minimum agreed LoD--Level of Detail) that includes digital representations of all relevant components of the asset. This model constitutes the Project Information Model (PIM), a vital tool for consolidating information about the current state of the asset;
* In the third stage, the PIM is further augmented with detailed information (e.g., history of previous interventions, material testing results, technical expertise, etc.) reflecting the current state of the asset; within this step, the PIM consolidates as the single source of truth for the project. In all subsequent steps, the ECM model is used by all project stakeholders (i.e., BIM specialists, architects, design engineers, project managers) to perform detailed analyses, identify potential problems and efficiently plan interventions, ensuring that they are carried out in a manner that minimizes risks and optimises resource use. All stakeholders involved in the development and implementation of a BIM project contribute to the development of related documents. For instance, considering that the OIR is usually an internal document of the appointing party, its content is not discussed during the project initiation phase, but the requirements stemming from it directly influence the content of AIR and PIR.