W4111 Database Systems Spring 2021 Homework 1, due 2/3/2021. 1. An ER-diagram designer comes up with the following argument. "Conventional entity sets model the world inaccurately because they group together entities that, at a finer level of granularity are different. For example, an entity set student mixes together many kinds of student (graduate/undergraduate, freshman/sophomore/junior/senior, CS-majoronmajor, residentonresident). Instead, we should be defining different kinds of fine-grained entities for every different variety of student, e.g., undergrad- senior-CS-major-resident-student. This would lead to a more accurate model because relationships can be tailored to connect only to the entity sets that are valid for that relationship." Explain why the design proposed by this designer is unsatisfactory. Make sure to describe all of the potential deficiencies of the design. Do you agree that the proposed design is "more accurate"? 2. Consider the following application description for a Twitter-like social network, and translate all of the information as precisely as possible into an ER diagram. Make sure that your diagram is unambiguous; e.g., that the TA can tell the difference between a double line and a single line. Clearly explain which (if any) information cannot be represented in the diagram. If you need to make any assumptions, state them clearly To post a message, a user must register as a member. Members have a name, email address and unique member-id. The same email address may not be used for two differ- ent members. Members can follow other members, at which time the follower can see all private messages posted by the member from the moment that the following relationship is established. Messages can refer to any number of prior messages via a message identifier. Messages can also refer to members via their member-id. A message, which contains up to 500 characters of text, may be public or private. Public messages are kept for one month in a repository that can be searched by any member using text keywords or a message ideni- fier. Private messages are transmitted only to followers and cannot be searched using text keywords. However, private messages can be retrieved by any member for up to one month using the message identifier, in order to resolve in-message links to prior messages. Members with over 1000 followers are labeled as "influencers" on their profile. Curators monitor mes- sages. Curators are a special, privileged group of members. The job of a curator is to delete offensive messages, and to add additional message-id links to messages that, in the opinion of the curator, are misleading. For internal review puroposes, the network keeps track of which curators deleted or modified various messages. Deleted messages are not visible to any members, even with a message-id