## 2 State of the Art
### Usage of Web Interfaces and BIM Data Exchange in AECO Industry  
The two most important criteria related to the openBIM approach are, as described in [PERSON] et al. [1], are the openness and neutrality of data standards. In the AECO industry, buildingSMART acts as a neutral body for the standardization of interfaces and data exchange standards in the field of BIM [30]. Relevant standards, such as the openCDE specification, are further developed, and new ones are being launched by buildingSMART. For the improvement of interoperability within the AECO software ecosystem, buildingSMART has developed several APIs. A major innovation is the openCDE-API family consisting of the already established BCF-API [31], a new Documents-API [32], and a basic Foundations-API [33]. The basis for the buildingSMART openCDE family is the German national DIN SPEC 91391-2 [9] (also known as the openCDE specification). It is an industry specification for the exchange of data in the context of shared data environments, specified by leading software companies in the field of CDEs. It describes the data exchange needed to synchronize CDEs with other applications, using RESTful API to exchange, store, and manage data with project partners. CDE fulfilling the requirements and API specification by DIN SPEC 91391-2 are denoted as openCDE [9]. The specification standardizes both technical functionalities through the use of data structures and protocols, as well as logical aspects through the use of workflows for data management. Furthermore, the openCDE specification [9] defines metadata for managing information containers and the inherent information contents in CDEs. It specifies a set of RESTful routes for obtaining the current version of the API, logging in and out, accessing projects, accessing different container types in projects and managing the respective information containers with GET and POST requests. Each time a container is posted, it either creates a new container or a new version of the container. There is no overriding or changingof containers possible according to the specification, which is defined in the versioning concept in DIN SPEC 91391-2 [9]. Furthermore, the specification defines use cases for the usage of the API. Basic functions of the openCDE-APIs are user management, the authorization and authentication process, as well as filtering, sorting and managing resources. The Foundations-API [33] also includes these basic functions and acts as a foundation for the BCF-API [31] and Documents-API [32]. The uploading and providing of documents can also be used in combination with the functions of the BCF-API. This API specializes the BCF and is used to document project-specific problems that occur during the modeling process of a structure so that they can be solved by project participants in the further course. For this purpose, the BCF-API provides functionalities to create these topics. Further functions are the management of comments, viewpoints and related documents. Building data, such as objects and processes, are modeled in the IFC schema to provide an open and vendor-neutral format for interoperability between BIM tools [3]. Currently, IFC files are manually exchanged using three data formats, including.ifc in step format,.ifcxml in XML format, and.ifcZIP with the PKzip 2.04 g compression algorithm [34]. The chosen serialization of an IFC file significantly affects the data transfer rate and performance of a system [35]. The study by [PERSON] et al. [5] on cloud BIM data integration and data exchange has shown that the model-based data exchange is a major challenge and that current methods do not fully exploit the potential of the cloud. In common web applications, individual services communicate via data serialized either in XML or JSON. The result of previous research studies was that JSON serialized data are processed much faster, and the parsing efficiency is much higher compared to XML [35; 36]. In response to these results, [PERSON] et al.