## 2 Related Work  
### Social Media in Situational Information  
Twitter is a well established source from which we can obtain real time information during crisis events [17]. Its messages are called blog posts or tweets containing 140 characters (now 280). Search parameters are used to find information in all posts (tweets). By incorporating Twitter data or Twitter streams into various research studies, researchers can produce various important public health information that can be used to analyze health predictions and trends. By allowing researchers to depend on user-generated information, researchers can detect and identify different online trends [18]. This type of information can be helpful in various ways, such as understanding the emotions of the public by identifying the tweets' sentiments during disasters; posts are classified in various ways, such as researchers classifying the sentiments of tweets during disasters through bayesian networks [19]. Situational information is generated and disseminated rapidly by users on social media. People make use of social media to give an opinion on something happening currently that is regarded as a hot trend in social media terms. As far as crises are concerned, during these helpful and situation-related information is disseminated by social media users in any form [10; 11]. Different authors categorized situational information from different points of view. For example, ref. [13] defined situational information as information that gives notification of the cases, casualties or victims of disasters or voluntary work, and categorized sympathizing with the victims, acknowledging voluntary work, providing relief packages, or donations into non situational information. However, in the study by [20], they classified the tweets' information by relevancy as relevant or non-relevant posts during disasters by applying the random forest algorithm for relevance classification; they called their approach contextual relevance classification of social media posts during crises or emergency situations. Tweets sometimes carry no hash-tags that are sometimes considered to be human labels, and most of the time fail to use the relevant keywords (e.g., COVID-19, \"coronavirus\", \"COVID\", etc.). So, in spite of related work on the situational information topic, we doubt that the current work or results are affected by complete absence of critical content of the context of interest (we are not implying that information is not present, we are just implying here that it is hard to detect this type of information in the first place) [21]. Situational information on social media makes it easy for decision-making authorities to prioritize, invest in and deploy supplies (food, water, and donations), services (emergency health cares, medical aid), and rapid response to emergencies like the COVID-19 Pandemic. To act in response to this type of situational information requires obtaining the details about affected areas, the number of cases (in COVID-19 context), and hospital capacities with the aim of creating an accurate representation of the situational information in specified areas in which it happened. This high level information is called situational awareness information [21]. Some researchers categorized this information into seven categories such as precautions/advice, casualties and damage, donations of money, goods, or services, people missing, found, or seen, and information sources [22]. In one study [11], they categorized 10 types of situational information such as voluntary work, information about the disaster, updates about the situation, criticizing, counter rumours, offers of help, sympathy with victims, donations, self support and preparations. Based on the views of the authors of [23], \"the text that contains the trending topics during the disaster time and right after the disaster time, that means the trending topic on Twitter during the disaster, classified as situational information, because it gives relevancy about the current event that is going on\".