## 4 Results and Discussion
### Rq3: What are the most widely used patent data collections? Researchers must consider various factors when selecting databases for patent search and retrieval processes. Key considerations include availability, open access, and ease of use of the database. The size of the database is crucial as larger databases offer broader coverage of prior art, enabling more comprehensive searches. These extensive datasets are also vital for training machine learning and natural language processing models. Specific dataset parameters, such as publication dates, patent classification codes, and keywords, are essential for refining search queries and effectively filtering results. These parameters allow researchers to target specific time periods and technical fields effectively. Additionally, precise annotations or classifications within the database enhance the efficiency of the retrieval process. Below is a list of data collections or datasets that have been used for evaluating patent retrieval systems in the surveyed research articles:  
* CLEF-IP The CLEF-IP ([[http://ifs.tuwien.ac.at/~clef-ip/](http://ifs.tuwien.ac.at/~clef-ip/)]([http://ifs.tuwien.ac.at/~clef-ip/](http://ifs.tuwien.ac.at/~clef-ip/)) URL (accessed on 29 March 24)) (Conference Labs of the Evaluation Forum--Intellectual Property) is an Intellectual Property (IP) track under the umbrella of CLEF ([[https://www.clef-initiative.eu/](https://www.clef-initiative.eu/)]([https://www.clef-initiative.eu/](https://www.clef-initiative.eu/)) URL (accessed on 29 March 24)) (Conference and Labs of the Evaluation Forum), which is a European series of workshops that commenced in 2001 to promote research on cross-language information retrieval (CLIR). CLEF-IP was conducted between 2009 and 2013 to evaluate the performance of patent retrieval (PR) systems. It offers datasets for various activities, including prior art searches and patent classification. The CLEF-IP data collection encompasses patent documents gathered from USPTO, EPO, and WIPO, presented in XML format with a common DTD structure. The documents include sections such as bibliographic data, abstracts, descriptions, and claims, often in multiple languages (English, German, and French), as required by the European Patent Office (EPO) for granted patents. This collection is organized in corpus and topic pools to aid the information retrieval community in comparing the efficacy of various information retrieval techniques [8; 123]. A more detailed explanation of the variants of the CLEF-IP dataset is given in Table S2 in Section S3.2 of the Supplementary Material [8; 123; 124; 125; 126]. Numerous studies [39; 42; 43; 45; 46; 48; 49; 56; 66; 73; 74; 79; 82; 83; 85; 87; 89; 94; 95; 96; 97; 98; 99; 100; 101; 102; 103; 104; 105; 106; 107; 108; 109; 110; 111; 111; 112; 113; 114; 115; 116; 117; 118] have utilized CLEF-IP as their dataset for experimentation and verification. * NTCIR The NTCIR ([[https://research.nii.ac.jp/ntcir/ntcir-12/index.html](https://research.nii.ac.jp/ntcir/ntcir-12/index.html)]([https://research.nii.ac.jp/ntcir/ntcir-12/index.html](https://research.nii.ac.jp/ntcir/ntcir-12/index.html)) URL (accessed on 29 March 24)) (NII Test Collection for Information Retrieval Research) workshop was first initiated in 1997 by the Japanese National Institute of Informatics to promote research in information retrieval (IR) and related fields, with a specific emphasis on cross-language information retrieval (CLIR) [8]. The Patent Retrieval Task aims to offer test sets for research on patent information processing, including retrieval and mining [127]. Table S3 in Section S3.2 of the Supplementary Material explains patent retrieval tasks in NTCIR-3, NTCIR-4, NTCIR-5, and NTCIR-6 [8; 127; 128; 129; 130]. Only one study [84] utilized the NTCIR-6 dataset.