# Integration of Cost and Work Breakdown Structures in the Management of Construction Projects
## 2 Literature Review
### BIM in the Construction Industry  
The implementation of BIM allows managing the construction project information (and its documentation) from the design phase to its maintenance and operation [121]. BIM has demonstrated its potential in several environments, such as facility management (FM) [122], lean management (LM) [123], and more recently in the railway industry [124]. The first reason is that BIM systems contain enriched information. This facilitates the exchange and interoperability of information making it capable of supporting multiple types of analysis, including PM analyses (e.g., scope, quality, schedule, cost, and risk) [111]. Thanks to the growing popularity of BIM, data automation (at least regarding acquisition and processing) is guaranteeing a more reliable, accurate, and precise scope definition and cost estimation. These aspects enable wider collaboration and more active participation of project stakeholders in all stages [11].  
In this context, where there is more available and reliable, but confidential, information, the whole construction process must be standardized. This can be done introducing a WBS in the BIM model [125]. The WBS has proven to be an excellent tool for the prevention and control of cost overruns, delays, and risk triggering [126], especially in combination with PM software [127]. Indeed, many BIM-based tools have been developed for construction scheduling and cost estimating [111], although most of them focus on product and element level [128].  
BIM-based WBSs have occasionally been introduced in construction (for example prototyping a linkage between the CBS and the WBS [125]). However, these have mostly focused on the product (the infrastructure or building) neglecting the management dimension. The integration of the CBS and the WBS must take into account this double dimension (the result and the necessary work to materialize it) [114]. However, the process classification system and the cost classification system must be assembled into BIM models. This means dimensional activities must be aligned to cost statements according to the combination of both WBS and CBS classification systems simultaneously. Fortunately, the object-oriented approach of modeling building information facilitates the standardization of different WBS databases [16].  
BIM offers the best automatic approach to generate accurate and direct quantity measurements from virtual models [129]. Management information such as progress, cost, safety, and quality is integrated via 3D models providing useful information for project managers [130]. Additionally, BIM adds many other engineering information database capabilities, such as storing architectural designs with geometric and technical information.  
However, a critical issue in current 3D BIM models is the discrepancy between the element breakdown structure (EBS) and the WBS of the project schedule. Integrating construction records into BIM remains a challenge due to their heterogeneous and unstructured data formats [131]. In fact, at the construction stage, a large number of construction reports are generated (e.g., schedule and cost reports, construction methods, site photos, shop drawings, change orders, etc.), but these are not properly integrated in the current as-built project documentation.