# An Inspection of IFC Models from Practice
## 5 Results
### Discussing Implications for Use Cases  
The results showed that, at the present situation, the direct use of models for automatic processing is very difficult. Looking more specifically at some of the use cases, other than visualization and building design, as exemplified in Section 3, we notice that a very small number of the inspected models could be used directly as-they-were within automatic tools. The accuracy of automatic calculation of building costs would be prevented for all but 5 models out of 39, for the combined quality of semantics (entities, attributes and use of _IfcBuildingElementProxy_) and materials (see Figure 4). Moreover, the low quality in geometry modelling and intersections would additionally affect this use case in at least 23 models out of the considered 57. Semantic and geometric inaccuracies could prevent the use of most of models also for the structural analysis use case. Entities were represented with a sufficient consistency in 36 out of 39 models, although they were assessed as fully consistent in only 23 models. However, the wide use of the generic class _IfcBuildingElementProxy_ in most of the models would make this information little usable anyway, and a manual check should still be necessary before going to any automatic processing. Materials (having sufficient representation in 30 out of 39 models) are also important to be added with their specific structural characteristics. Again, when considering all those semantic features together, no more than five models could be considered sufficient for automatic processing. Finally, grouping of elements was of importance: 15 out of 50 models reached the minimum score for _IfcBuildingStoreys_ grouping. For energy simulations, the materials were not properly specified in nine cases. The modelling of spaces was also important for this use case, but in 70% of models this  
Figure 7: Distribution of models according to the quality of _IfcSpace_ use. information could not be properly used and in an additional 10% human editing was necessary to choose among the redundantly modelled spaces. At least an approximate georeferencing was necessary for this use case (minimum yellow in Table 3) for both planar coordinates and elevation. Only 10 models out of the whole sample had this property, without considering a minimum for the _LoGeoRef,_ so that a _LoGeoRef10_ (the address) was also considered as a valid indication. Moreover, in half of the 10 cases, redundant but less accurate or wrong georeferencing information was stored according to different _LoGeoRefs_ (see as example the models n.9 or 10 in Table 3). In those cases, human intervention would be necessary anyhow in order to select the correct alternative. For urban planning, correctness of semantics (at least consistency of entities) was necessary, for which the same considerations applied as for the structural analysis use case. With respect to the grouping of storeys, 15 out of 50 models reached the minimum score about the use of _IfCBuildingStorey,_ however, 11 out of them presented elements occupying more than one storey, although this was not a modelling error per se. In addition, the representation of spaces was important, for which the same comments as for the energy simulations use case applied and the quality of geometric modelling did not help: intersections and further irregularities could be noticed in at least half of the inspected models. Georeferencing in this case must be very accurate (green in Table 3) and store rotation as well. This means that only five models met the necessary requirement. An additional four could be considered in case they were modelled considering the correct orientation, but there was no way to check this. Additionally, in this case, all five models presented concurrent storage of wrong or less accurate information as different _LoGeoRefs,_ that should probably be checked and adjusted manually.