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