Suppose we have a Web server that has the data of the web pages stored inside a database, and not in operating system files. The pages are retrieved through queries when needed. The schema of the Web server application is:

Page(Page ID: number(4) not null, Path: varchar(80) not null, Owner: varchar(15) not null, Last Modified: date not null, text: long not null) contains an entry for every web page on the server: An identifying number, a path, the owner, the date of last modification, and the text of the page (the HTML source code). Request(Request No: Number(5) not null, IP: varchar(15) not null, when: date, Page ID not null) is used to log requests for web pages: Whenever a browser requests a web page, the IP address of the requesting machine, a timestamp (attribute when) and the ID of the page are stored in the table Request. The requests are numbered and the number served as Keyword(Word: varchar(10) not null, Page ID: number(4) not null): is used for a local search function: It contains keywords (search terms) for each A page can be described by any number of keywords. Express the following Queries in Algebra List the keywords used by John List the keywords not used by John For every owner, list the day of the very last update of a page along with the Page ID (note that we do not want the update date for all the pages. If an owner has 2 pages, P1 was updated on January 20, 2021 and P2 was updated on February 2, 2021, we want only P2 to be returned) List pairs of owner with at list one page sharing common keywords along with the pages (make sure not to include redundant information). Which IP addresses never accessed Johns Web Which keywords are used by all the page owners (in at least one of their pages)? Which owner has at least one of his/her pages accessed by all the IP addresses?