## 4 Results and Discussion
### Gaps Related with Digital LCA Data
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Gap** & **Name** & **Analysis** \\ \hline \multirow{4}{*}{6} & Unique identification of the & \begin{tabular}{c} The options for the RSL should be predefined in the relevant PCR and provided in \\ the digital format as enumerated values. It can be based on parameters to be \\ declared in the EPD. The RSL should also include any conversion factors required \\ to transform the functional or declare unit into a usable quantity at building level. \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} Information modules, defined in \\ CEN/TC 350 or ISO/TC 59/SC 17 \\ standards, not included in IFC 4.3 \\ \end{tabular} \\ \hline \multirow{4}{*}{8} & Parametric definition of all the & \begin{tabular}{c} IFC should include parameters for general properties, but the parameters specific \\ for a product family should be defined in the relevant PCR. Therefore, this gap \\ cannot be resolved solely by revising the IFC schema. \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} Unique identification of the \\ constituent materials, including \\ their percentage in mass \\ or volume \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} The unique identification of materials should be globally recognized to ensure \\ interoperability. Therefore, this gap cannot be resolved solely by revising the IFC schema. \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} Unique identification of the \\ constituent materials, including \\ their percentage in mass \\ or volume \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} The unique identification of materials should be globally recognized to ensure \\ interoperability. Therefore, this gap cannot be resolved solely by revising the IFC schema. \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} Unique identification of the \\ constituent materials, including \\ their percentage in mass \\ or volume \\ \end{tabular} \\ \cline{2-3}  & \begin{tabular}{c} The identification of LCA sources should be globally recognized to ensure \\ interoperability. Therefore, this gap cannot be resolved solely by revising the IFC schema. \\ \end{tabular} \\ \cline{2-3}  & \
\begin{tabular}{c} Identification of any LCA \\ databases or sources for \\ background data \\ \end{tabular} \\ \cline{2-3}  &
\begin{tabular}{c} The declaration of this information should be globally standardized in a revision \\ of ISO 22057. The PCR should include the relevant criteria for this information, \\ which should then be used to compare the assumptions with the actual building. \\ This will help determine if the information can be transferred with modifications. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Gaps related to the LCA information. The gaps identified in Tables 1-3 are common to most formats used to manage dEPDs and are not always relevant for the IFC model of a built asset. However, when IFC is used to transfer product information in a manufacturer's catalogue, all the elements above apply. Therefore, unless a specific format for product data aligned with IFC is defined, the standardized schema should be able to store this data. According to [PERSON] et al. [45], EPDs also present limitations due to the lack of uniformity in the criteria used to calculate their LCA or the uncertainties associated with the use of different background databases, together with the human factor. However, the limitations inherent to current EPDs are not part of this study, which only covers their machine-interpretability. [PERSON] et al. [46] concluded that a new data structure should be developed, with a view to aligning it with the BIM and LCA fields. This structure should include improved and unified naming conventions. The study highlights the current situation, in which the transfer of data from BIM models to LCA tools is dependent on manual processes. This approach is susceptible to unexpected errors, including information loss and deviations in the BIM models.