Diagrams with zoom

         sequenceDiagram
     participant web as Web Browser
     participant blog as Blog Service
     participant account as Account Service
     participant mail as Mail Service
     participant db as Storage

     Note over web,db: The user must be logged in to submit blog posts
     web->>+account: Logs in using credentials
     account->>db: Query stored accounts
     db->>account: Respond with query result

     alt Credentials not found
         account->>web: Invalid credentials
     else Credentials found
         account->>-web: Successfully logged in

         Note over web,db: When the user is authenticated, they can now submit new posts
         web->>+blog: Submit new post
         blog->>db: Store post data

         par Notifications
             blog--)mail: Send mail to blog subscribers
             blog--)db: Store in-site notifications
         and Response
             blog-->>-web: Successfully posted
         end
     end