# Overview of Blockchain Oracle Research
## 1 Introduction  
\"Although oracles play a critical role... the underlying mechanics of oracles are vague and unexplored\" [1]. A preliminary study on Decentralized Finance (DeFi) oracles from the University of Singapore shows that despite the massive amount of money managed by oracles on DeFi platforms, their functions and roles are still widely neglected. Despite the plethora of papers involving blockchains, less than 15% consider oracles, and an even smaller percentage further investigated related issues [2]. The subject of blockchain oracles is critical because the entire concept of blockchain applications revolves around the idea of decentralization and trustless transactions. Those pillars, however, are undermined when, gathering real-world data, blockchain applications rely on centralized and trusted third parties. This issue, either addressed as an oracle problem [3] or an oracle paradox [4], makes the community of blockchain enthusiasts quite skeptical about real-world applications [5]. Proposing a robust blockchain application against the oracle problem requires the redaction and discussion of the so-called \"trust model\", a document or scheme that broadly explains how data are fetched by oracles in a decentralized and trustless manner [6; 7; 8; 9]. A robust trust model should first include information concerning how data collected by oracles are validated before being pushed into the smart contract. Second, it should specify how the security and unforgeability of data are ensured from the time they are collected to the moment they are permanently stored on the ledger. Third, it should outline the incentive mechanism implemented to prevent collusion or the deliberate tampering of data feeds for selfish purposes [9; 10; 11]. Defining and adopting a robust trust model is not only essential for a blockchain application to work properly but is also often considered the key to mass adoption [12]. However, academic contributions concerning oracles or those discussing a detailed \"trust model\" [2] remain scarce. On the one hand, proposing a real-world blockchain application without analyzing the oracle's role in depth poses serious doubts about the feasibility and genuineness of the underlying project [13]. On the other hand, proposals with a detailed trust model would greatly help researchers andpractitioners analyze oracle-related features and issues and reproduce successful projects respectively [14]. Therefore, knowing which institutions are actively undertaking research on blockchain oracles and which ones are already implementing them in real-world applications is interesting and important. Scholarly interest in blockchains has resulted in some literature reviews on this topic, but none has yet undertaken research through a bibliometric analysis on blockchain oracles [15; 16; 17]. A bibliometric analysis aims to identify how the body of knowledge on blockchain oracles has evolved in the last few years in terms of the leading publication outlets, the geographical distribution of research communities, the density of collaboration, and methodological approaches. Unlike classic literature reviews, a bibliometric analysis provides a quantitative and structural overview of the investigated scientific field, reducing the chances of subjective biases [18]. The advantages of undertaking this type of study are the representation of a phenomenon in a formal and objective way, ensuring the robustness and reproducibility of results. A bibliometric analysis is also meant to guide scholars who are interested in undertaking research in that sector to understand the research gaps, methodologies used, and appropriate outlets for publication. To ensure the significance, usability, robustness, and replicability of the research study, this paper will follow a standard bibliometric approach that has been used in several studies across different disciplines [19; 20; 21; 22; 23]. The methodology will be extensively explained so that any individual can reproduce every passage, regardless of their expertise.