# A Review of the Development and Future Challenges of Case-Based Reasoning
## 3 Development of CBR Key Technologies
### Case Representation
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & **Element** & \multicolumn{2}{c}{**Representation**} & **Limitation** \\ \hline \multirow{8}{*}{Frame} & \multirow{4}{*}{slot 1:} & \(<\)Frame name\(>\) & \\  & & & facet 1\({}_{1}\) & value 1\({}_{11}\), value 1\({}_{12}\), \(\cdots\) & \\  & & & \(\vdots\) & \\  & & & \(\vdots\) & \\  & & & \(\vdots\) & \\  & & & \(\vdots\) & \\  & & & slot n: & facet n\({}_{1}\) & value n\({}_{11}\), value n\({}_{12}\), \(\cdots\) & \\  & & & \(\vdots\) & \\  & & & facet n\({}_{m}\) & value n\({}_{m1}\), value n\({}_{m2}\), \(\cdots\) & \\  & & & constraint condition & \\ \hline \multirow{8}{*}{Oriented} & \multirow{4}{*}{CLASS:\(\cdots\)ID, DS, MS, MI\(>\) ID: Identifier DS: Data Structure MS: Method St: Message Interface} & class \(<\)name\(>\)[\(<\)Superclass\(>\)] & \\  & & & [\(<\)Class variable name\(>\)] & \\ \cline{1-1}  & & & Structure \\ \cline{1-1}  & & & ID: Identifier & \(<\)Static structure description of an object\(>\) \\ \cline{1-1}  & & & DS: Data Structure MS: Method St: Message Interface & Method St: Message Interface & \\ \cline{1-1}  & & & \(<\)Definition of an operation on an object\(>\) & \\ \cline{1-1}  & & & Restraint & \\ \cline{1-1}  & & & \(<\)Restricted condition\(>\) & \\ \hline \multirow{4}{*}{Production Rule} & \(<\)production\(>:=\) & & \(\text{P}\)\(\rightarrow\)Q & Low efficiency; \\ \cline{1-1}  & \(<\)precondition\(>\) & & & \(\text{Unable to express}\) \\ \cline{1-1}  & & & \(<\)conclusion\(>\) & IF P THEN Q (CF = [0, 1]) CF: Certainty Factor & structured knowledge \\ \hline \multirow{4}{*}{Semantic Nets} & \multirow{4}{*}{(Node1, Arc, Node2) Semantic Relation} & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{\
\begin{tabular}{} \end{tabular} } \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \hline \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & \multicolumn{2}{c}{Predicate-Based} & \multicolumn{2}{c}{Predicate (Con- & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \end{tabular}
\end{table} 
Table 1: Case representation methods. representation in medical information [23]. At the same time, in the era of big data, the massive flood of information has led to a surge in the number of cases; consequently, the description of case information is messy, and the scale of the case base is expanding [24]. In the face of this situation, these mature case representation methods are more applicable to cases with simple structures, single representation methods, and fewer parameters, and cannot be applied well to complex and changeable cases. Therefore, many scholars have begun to study new methods to solve the above problems. On the one hand, based on the existing case representation method, new improvement strategies have been proposed to achieve the complex representation of cases in combination with other AI methods according to the actual application. For example, a framework case representation method integrating multiple information enhances the representability of the case [25]. A multi-strategy ontology mapping method can be applied to realize the semantic expression between the process knowledge graph and the entity model [26]. An association representation between cases is added to case representation [27]. However, the problem is that improved methods are often aimed at a specific application field, which requires domain-specific knowledge in order to build a model. This method is complex and only applicable in a small range of cases. Second, it increases the workload of the case representation process. For ordinary users, it is often difficult to manipulate the model. Finally, there are many improvement methods, but explanations of their advantages and disadvantages are lacking. Therefore, choosing different AI methods is a problem that must be considered.