Consider Twitter, it is a social network platform where user sends tweets of 280 characters.

• Each tweet may have a number of hashtags. (a hashtag is a string starting with #)
• We record the time and location of each tweet.
• A tweet may include up to four media items (either a photo or a video)
• A tweet may refer to a user
• Tweet can be a reply to another tweet
• User can follow user or hashtags
• To use Twitter, a user must register by his(her) email, phone number, and user name.
• Design an entity-relationship diagram.

Symbol Meaning Entity Composite Attribute Weak Entity Derived Attribute Relationship E R E2 Total Participation of E, in R Indentifying Relationship N E R E Cardinality Ratio 1: N Attribute =1 E, entity can be related to N E, entities 9 99 (min, max) E Key Attribute R Structural Constraint (min, max) on Participation of Ein R Multivalued Attribute