# A Purely Entity-Based Semantic Search Approach for Document Retrieval
## 3 Materials and Methods
### Retrieval and Ranking Method
#### 3.3.3 Algorithm
So, the four average score classes are (min = 0.65, 0.85, 0.95, and 1.00) and (min = 0.50, 0.65, 0.70, and 0.75) for DBpedia Spotlight and REL, respectively. Moreover, for each of these average scores, the corresponding query numbers are (154, 132, 109, and 3) and (12, 9, 4, and 2), respectively, for each method. We note that DBpedia Spotlight tends to assign higher scores than the REL tool; thus, we assigned the average score class values of DBpedia Spotlight a higher place than those of the REL entity linker. Finally, for both entity linkers, the completely annotated queries were separately classified into these different classes. Figure 3 shows the performances of PES4 IR and the Galago (Dirichlet model) according to each class of queries, where the PES4 IR queries are annotated by the DBpedia Spotlight and REL entity linkers (respectively in (a) and (b)). In the figure, the performance is presented by the NDCG@20 scores. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Entity Linking Method** & \
\begin{tabular}{c} **\#Completely** \\ **Annotated Queries** \\ \end{tabular} &
\begin{tabular}{c} **\% of Completely** \\ **Annotated Queries** \\ \end{tabular} & **Usage** \\ \hline DBpedia Spotlight & 180 & 72\% & Spotlight Python Library (v0.7) 1 \\ REL & 17 & 6.8\% & Python API 2 \\ \hline \hline \end{tabular}

* [[https://pypi.org/project/spotlight/](https://pypi.org/project/spotlight/)]([https://pypi.org/project/spotlight/](https://pypi.org/project/spotlight/)); 2 [[https://github.com/informagi/REL](https://github.com/informagi/REL)]([https://github.com/informagi/REL](https://github.com/informagi/REL)). Accessed on 2 August 2023.

\end{table} 
Table 4: Completely annotated queries by DBpedia Spotlight and REL for Robust collection queries. In Figure 2(a), Galago (Dirichlet model) outperforms our approach for the first three classes of queries, where the queries are annotated by the DBpedia Spotlight entity linker. However, for the last query class, PES4 IR outperforms Galago, where the average annotation score of that class is equal to (1.0). The corresponding nDCG@20 scores are provided in Table 5, with more details. In Figure 2(b), for the last queries class, which corresponds to average annotation scores larger than or equal to (0.75), PES4 IR outperforms the Galago method. Moreover, the corresponding nDCG@20 scores are listed in Table 6.

From the perspective of a retrieval system based on a multi-method approach, which leverages different approaches (such as the retrieval method) for better document information retrieval, PES4 IR could be leveraged for the well-represented queries (queries with high annotation scores, such as the class of the highest average annotation scores, in (Tables 5 and 6)), and other methods for the rest of queries. In fact, due to its autonomy, the PES4 IR approach could be used alongside any other document retrieval \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Method**} & \multicolumn{4}{c}{**nDCG@20**} \\ \cline{2-5}  & **AVGs \(\geq\) Min** & **AVGs \(\geq\) 0.65** & **AVGs \(\geq\) 0.7** & **AVGs \(\geq\) 0.75** \\  & **(12 Queries)** & **(9 Queries)** & **(4 Queries)** & **(2 Queries)** \\ \hline Galago (Dirichlet) & 0.4216 & 0.4500 & 0.4360 & 0.6759 \\ PES4 IR & 0.3036 & 0.3670 & 0.4038 & **0.7306** \\ \hline \end{tabular}
\end{table} 
Table 6: nDCG@20 scores for queries’ classes given by REL. Figure 3: nDCG@20 retrieval scores for queries annotated by DBpedia spotlight and REL ((**a**) and (**b**), respectively). \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Method**} & \multicolumn{4}{c}{**nDCG@20**} \\ \cline{2-5}  & **AVGs \(\geq\) Min** & **AVGs \(\geq\) 0.85** & **AVGs \(\geq\) 0.95** & **AVGs \(\geq\) 1.0 (3 Queries)** \\ \hline Galago (Dirichlet) & 0.3498 & 0.3643 & 0.3839 & 0.5702 \\ PES4 IR & 0.2160 & 0.2257 & 0.2355 & **0.6207** \\ \hline \end{tabular}
\end{table} 
Table 5: nDCG@20 scores for queries’ classes given by DBpedia spotlight. method. Table 7 illustrates the added value of PES4 IR when it is used alongside Galago.