## 3 DL-Based Ontology
### Entities for Model Slicing  
Model slicing is a process planning task that aims to truncate the build model (i.e., a 3D model with support structure) into a set of thin slices that best meet the build and quality requirements to build a part [6]. The main inputs of this task include an LPBF machine, a 3D model with support structure in a build orientation for a part to be built, and specific build and quality requirements on the part. Its outputs are a set of thin slices. A slice corresponds to a layer of the part to be built. The main attributes of a slice are its  
Figure 5: An ontological view of support generation for LPBF. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Data Relation** & **Domain** & **Range** & **Meaning** \\ \hline _hasSupportedArea_ & _3 dModel_ & _SupportedArea_ & A 3D model that has supported area of \\ _hasDetectionMethod_ & _SupportedArea_ & xsd:string & A supported area that has detection method of \\ _hasSupport_ & _3 dModel_ & _SupportStructure_ & A 3D model that has support structure of \\ _hasGeneration Tool_ & _SupportGeneration_ & xsd:string & A support generation task having generation tool of \\ _hasOptimisationMethod_ & _SupportStructure_ & xsd:string & A support structure having optimisation method of \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Domain, range, and meaning of five relations in support generation. contour and thickness. This thickness is usually called layer thickness, which is one of the critical LPBF process parameters. The output slice information is generally encoded in a proprietary format [22], such as the CLI (common layer interface), SLC (stereo lithography contour), and HPGL (Hewlett-Packard graphics language) format. The simplest model slicing strategy is uniform slicing in single direction, which truncates the build model into a set of slices with equal thickness along the direction perpendicular to the build orientation. It is the first model slicing strategy in AM and is the most widely used strategy in industry [6]. The biggest advantage of the uniform slicing in single direction is that it is simple, efficient, and robust. However, this strategy would lead to a loss of control over the part accuracy, since it neglects the actual geometry of the build model [55]. In the past few years, a number of improvement strategies were developed [76; 77; 78], where representative ones are uniform slicing in multiple directions, variable slicing in single direction, and variable slicing in multiple directions. Each strategy has its specific characteristics. Generally, a slicing strategy is selected based on actual objectives [6]:  
* if the objectives of model slicing are normal accuracy and high efficiency, then uniform slicing in single direction (ussd) is recommended;
* if the objectives of model slicing are normal accuracy, reduced support, and alleviated anisotropy, then uniform slicing in multiple directions (usmd) is recommended;
* if the objective of model slicing is high accuracy, then variable slicing in single direction (vssd) is recommended;
* if the objectives of model slicing are high accuracy, free of support, and alleviated anisotropy, then variable slicing in multiple directions (vsmd) is recommended. To represent the knowledge in model slicing, two concepts named _SliceContour_ and _SlicingStrategy_, three relations listed in Table 6, and four instances named _ussd_, _usmd_, _vssd_, and _vsmd_ (instances of _SlicingStrategy_) were created. Based on these entities, an ontological view of model slicing for LPBF is delineated in Figure 6, and four SWRL rules for recommending a model slicing strategy were developed as follows:  
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