# Combined MvdXML and Semantic Technologies for Green Construction Code Checking
## 4 Methodology of Green Construction Code Checking
### Conceptual Model Ontology  
Conceptual model ontology is to extract related concepts from building standards, construction documents, and BIM models, before using the ontology modeling method to build the relationship model of green construction concepts. Through analyzing the relationship between the green construction concepts, the relationship can be described by rules. During green construction code checking, when the information is input to the inference engine, the chosen concepts represent a series of potential requirements. These concepts are regarded as a series of hierarchical concepts, and some semantic relationships exist between concepts. The implementation of inference rules can infer and identify the necessary concepts and their relationships. Therefore, through the analysis of the characteristics of green construction, the conceptual model ontology includes two parts: (1) structure of concepts; (2) definition of semantic relationships. (1) Structure of concepts  
The first task of conceptual model ontology construction is to define the classification of concept structure and hierarchy structure related to green construction. Based on the previous studies and the characteristics of green construction, this paper defines the relevant attributes of the main classes and their sub-classes including project classification, building product, building feature, etc. (2) Definition of semantic relationships  
When the relationship between concepts is defined, the relationship should be associated with richer semantics. The semantic relationship describes the relationships between concepts in ontology, which can be divided into hierarchical and non-hierarchical [50; 51]. The relationship between classes can be divided into internal and external. Through the analysis of the definition of semantic relations, the semantic relations in green construction field are mainly divided into two kinds: hyponymy (also expressed as superclass-subclass) and association. Association can be mainly divided into synonymy relationships (also expressed as Equivalent (\(x\), \(y\))), antonymy relationships (also denoted as Disjoint (\(x\), \(y\))), and meronymy relationships (also expressed as Whole-Part (\(x\), \(y\))). The following is a brief introduction to these relationships:  
(1) Equivalent (\(x\), \(y\)) is used to describe the similarity between two concepts. (2) Disjoint (\(x\), \(y\)) is used to describe the relationship of independence or antinomy between two concepts. (3) Whole-Part (\(x\), \(y\)) is used to describe the meronymy relationship between two concepts. A work item is the smallest unit of work defined for building elements in a construction project. The work item can be applied to separate phases from design to operation. The classification of workitems is according to national standards for project coding and project naming. A construction process may consist of one or more sub-processes, and a sub-process may consist of a collection of work items for multiple building elements. To establish the ontology of work items, the proposed ontology needs to know the corresponding work items and the corresponding amount of resources necessary. Therefore, the construction of work item ontology can facilitate green construction inspection. Existing work item ontologies, such as FreeClassOWL ontology, are built based on datasets from the European building and building materials market [52]. By describing the building products and services, they can satisfy a wide range of products, suppliers, warehouses, and other related construction product search needs. More than 88 million triplet business data, 81 product brands, 19 distributors, 56,360 product types, and 1,783,798 products are described in the FreeClassOWL Ontology. Therefore, the work item ontology is huge in terms of scale. During the construction process, participants who have rich knowledge and experience need to be gathered to define the ontology model.