OBRAS CONSULTADAS Alsina Thevenet, Homero

As design team members rely on their own discipline specific software to build and manage their models, it is necessary that there is movement of information from one BIM application to another (Cheung et al., 2012; Matipa et al., 2008). The smooth sharing of information across all BIM applications and disciplines (where different software can recognise the product of another) is described by Arayici et al. (2011) as ‘interoperability’. Cheung et al. (2012) view interoperability as the key underpinning of BIM, because it allows various stakeholders to work together by exchanging information, even if they are working with different applications. Taylor & Bailey (2011) note that interoperability’s importance in BIM is based on how information can be exchanged for the beneficial reuse for another. If this process is lacking or data is lost in that exchange full collaboration cannot be realised (Smith, 2014). Eastman et al. (2011) explain that in order for collaboration to be efficient and effective, the object based data exchange needs to include geometric shape,

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specification, parametric properties, a classification structure, assembly data and the overall design intent - so that this information can be extracted and utilised by other stakeholders in the supply chain. Goucher & Thurairajah (2012, p. 3) found that interoperability is currently underdeveloped and is a major issue “that BIM adoption has got to deal with”. Crotty (2012) outlines the need for agreed exchange formats to

be used in all key applications.

Bylund and Magnusson (2011) claim that there are two approaches to interoperability and data exchange. They state that users can either stay in one software vendor’s product range and use their specific file formats or use software from various vendors that can exchange information in a common language. Matipa et al. (2010) clarify an example of this first approach would be the exchange of proprietary DXF (Data eXchange Format) files between the Autodesk product range, such as ‘Revit’, ‘Navisworks’ and ‘Autodesk QTO’. Howell & Batcheler (2005) emphasise that this type of collaboration can be difficult to achieve because it is rare that all the design and construction team will be using one application or one vendor’s product range.

Bylund and Magnusson’s (2011) second approach describes a more flexible process where open-proprietary file formats can be exchanged between different applications. An example of an open proprietary file format is a Portable Document Format (PDF). However, this is a vector format, which only contains geometry rather than data, thus it would not constitute a BIM data exchange under the definitions of BIM outlined above (Crotty, 2012; Eastman et al., 2011; NIBS- BuildingSMART alliance, 2012).

Goucher & Thurairajah (2012) say that open–proprietary data exchange has been improved through the establishment of Industry Foundation Class (IFC), which is a common data ‘schema’ that makes it possible to exchange data between different proprietary BIM software applications. Sawhney (2014, p.15) defines a ‘schema’ “as a formal structure of a defined set of information”. IFC is developed by

BuildingSMART International (BSI) (formerly the International Alliance of Interoperability), an international not-for-profit organisation which constructs and supports what they describe as ‘Open BIM’ (BuildingSmart; Dhillon, Jethwa, & Rai, 2014; Wijayakumar & Jayasena, 2013). As an open format, IFC does not belong to a single software vendor, it is neutral and independent of a particular vendor’s native

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format and plans for software development (BuildingSmart, n.d). The IFC language is specified using the EXPRESS data definition, as defined by ISO103-11:1994 (Dhillon et al., 2014; Eastman et al., 2011). Sabol (2008) states that IFC is now recognised as an internationally accepted framework to facilitate information exchange among participants throughout the built asset’s entire lifecycle. IFC has gone through a number of evolutions, with the newest version IFC4 published in 2013 as ISO 16739:2013 (BuildingSmart; Dhillon et al., 2014). At present, many BIM software vendors have integrated IFC importers/exporters within their applications. This enables models to be imported and exported from BIM authoring applications, such as Autodesk Revit into 5D estimating applications such as Exactal CostX, Autodesk QTO and Nomitech CostOS (Dhillon et al., 2014; Fu et al., 2007).

However, IFC is not without issues. A number of authors comment that IFC does not completely solve the problem of interoperability as there is a degree of data loss through the exchange of information between heterogeneous software (Eastman et al., 2011; Redmond et al., 2011). Cheung et al. (2012) explain that this can happen due to the lack of uniformity between object schemas adopted between individual BIM tools and the IFC objects and properties. Redmond et al. (2011) claim that true interoperability will only be achieved when every software being used on a project can read and write to and from a centralised web hosted database by standardising the process of passing information between stakeholders and representing the latest information on the project.

Open-proprietary file formats such as IFC are a ‘collaboration benefit’ from a technological perspective, but they do not fully address all the implementation issues when adopting a BIM approach (Moore, 2015). Moore (2015) and Eastman et al. (2011) agree that a ‘collaborative working environment’ needs to be promoted to help teams produce information in a consistent format and at certain designated stages throughout the lifecycle of the built asset. A collaborative working environment is achieved through the production of co-ordinated design and construction information, providing order to the information flow for all those involved. This is achieved through ‘collaboration exchange standards’, where teams agree to produce information using standard processes and agreed standards and methods to ensure a consistent form and quality of information in a timely manner (BSI, 2013b). Collaboration exchange standards can take the form of a bespoke

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agreed protocol; a BIM execution plan or the adherence to published jurisdictional standards or guidance documentation (Moore, 2015).