Discuss how time is represented in temporal databases and compare the different time dimensions.

-

Temporal data stored in a temporal database is different from the data stored in the non-temporal database in that a time period attached to the data expresses when it was valid or stored in the database. As mentioned above, conventional databases consider the data stored in them to be valid at a time instant now, they do not keep track of past or future database states. By attaching a time period to the data, it becomes possible to store different database states. In the temporal base, database time is represented as an ordered sequence of points in granularity. It is determined by the application and for particular applications, temporal database researchers used the term ‘chronon’ in state of point to describe the minimal granularity.



Comments

Post a Comment

Popular posts from this blog

Suppose that a data warehouse for Big-University consists of the following four dimensions: student, course, semester, and instructor, and two measures count and avg_grade. When at the lowest conceptual level (e.g., for a given student, course, semester, and instructor combination), the avg_grade measure stores the actual course grade of the student. At higher conceptual levels, avg_grade stores the average grade for the given combination. a) Draw a snowflake schema diagram for the data warehouse. b) Starting with the base cuboid [student, course, semester, instructor], what specific OLAP operations (e.g., roll-up from semester to year) should one perform in order to list the average grade of CS courses for each BigUniversity student. c) If each dimension has five levels (including all), such as “student < major < status < university < all”, how many cuboids will this cube contain (including the base and apex cuboids)?

-
Image
a) A Snowflake Shema is shown in figure below: b) The specific OLAP operations to be performed: 1. Roll-up on course from course_id to department. 2. Roll-up on a student from student_id to university. 3. Dice on course, student with department ="CS" and university = "biguniversity" 4. Drill-down on a student from the university to student_name. c) N = 4 dimensions The cube will contain 54 = 625 cuboids.
Read more

Suppose that a data warehouse consists of the four dimensions; date, spectator, location, and game, and the two measures, count and charge, where charge is the fee that a spectator pays when watching a game on a given date. Spectators may be students, adults, or seniors, with each category having its own charge rate. a) Draw a star schema diagram for the data b) Starting with the base cuboid [date; spectator; location; game], what specific OLAP operations should perform in order to list the total charge paid by student spectators at GM Place in 2004?

-
Image
  b) The specific OLAP operations to be performed are: 1. Roll-up on date from date id to year. 2. Roll-up on spectator from spectator id to status. 3. Roll-up on location from location id to location name. 4. Roll-up on the game from game id to all. 5. Dice with status= “students”, location name= “GM Place”, and year=2004
Read more

What is national data warehouse? What is census data?

-
Image
National Data warehouse   A large number of national data warehouses can be identified from the existing data resources within the central government ministries. These are potential subject areas in which data warehouses may be developed at present and in the future. Census Data Census data can help planners and others understand their communities' social, economic, and demographic conditions. Census data is the primary data used by planners to understand the social, economic, and demographic conditions locally and nationally. We sometimes think the census is unique to the United States, but census data is collected in other countries.  The total process of collecting, compiling, and publishing demographic, economic, and social data about a specific time to all people in a country or fixed or defined area part of a country. Most countries also include a housing census. A census is a procedure of systematically acquiring and recording information about the members of a given populat
Read more