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CUSTOMER_CODE SMUDE DIVISION_CODE SMUDE EVENT_CODE APR2016 ASSESSMENT_CODE MCA3020_APR2016 QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 18253 QUESTION_TEXT Explain Temporal Database and Multimedia Database. SCHEME OF EVALUATION Temporal Database: Temporal databases are used to record timereferenced data. Basically, majority of the database technologies are temporal. For example: Record keeping function (inventory administration, medical-record and personnel); Financial function (banking, accounting and portfolio organization); Scientific function (Weather monitoring), Scheduling function (project organization, hotel, airline, and train reservations) all these functions trust on temporal databases. (2 marks) Temporal databases are best suited for the applications where information as to organize on time constraints. Therefore temporal database set a good example to demonstrate the requirement for development of a combined set of concepts for the use of application developers. The training of temporal database is designed by application developers and designers. There are numerous applications where time is an important factor in storing the information. For example: Insurance, Healthcare, Reservation Systems, and Scientific Databases. (2 marks) In case of temporal applications, even the two instances utilized might be simply expanded. For example, in COMPANY database, it might be desirable to keep PROJECT, JOB, and SALARY histories of all the employees. It can be applied to UNIVERSITY database as well, to store the grade history of STUDENT. The details about the YEAR, SEMESTER, COURSE and each SECTION are also included in this database.(1 mark) Multimedia Database: Multimedia databases facilitate the users to store as well as generate query for retrieving multimedia information. This information can demand for: Documents (like articles/books/journals), Images (like drawings/pictures), Video Clips (like newsreels/movies/hone videos); Audio clips (like speeches/ phone messages/ songs).(1 mark) The primary type of database query generally tries to locate multimedia sources comprising of particular objects of interest. Such as, one user wants to locate all the video clips regarding aa specific person, say Michael Jackson in a video database. Another scenario may be as of someone willing to retrieve video clips grounded on specific activities like, video clips where a soccer goal is scored by a certain player or team. These type of queries are mentioned as content based retrieval, as they retrieve information bases on a certain activity/object from the multimedia sources. (2 marks) To make this retrieval fast, the multimedia database must make use of some model to index and manage multimedia sources grounded on the contents. But identifying the contents of multimedia sources is lengthy and difficult task. To accomplish this task, two approaches can be followed as defined below: 1.Based on automatic analysis of the multimedia sources. It is done to recognize the contents mathematical characteristics. 2.Based on manual identification of the objects and objectives of interest in each multimedia source. And later on depending on this information index the sources. (2 marks) QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 73629 QUESTION_TEXT What are the different models of DBMS? State two advantages of each type. SCHEME OF EVALUATION 5 models with advantages - >2 marks each. Any two advantages among those mentioned below may be written Hierarchical Simplicity (simple design process since data consists of hierarchical relationship), Security (can execute the changing level of security characteristics), Database integrity (possible due to inbuilt structure of parent and child), Relationship handling (proficient for relationships of the type 1:M) Network Simplicity (simple design process since instances of data relationship occur as N:M type), Flexibility (more flexible as you can navigate data items in many ways), Standards (include development of worldwide standards), Relationship handling (proficient for relationships of the type N:M – popular in real data relationship situations) Relational Simplicity simple design process since easy to handle RDBMS), Flexibility (more flexibity), Follow every mathematical theory (obeys theories in maths), Relationship handling (can handle any every type of relationship) Object relational Reusability (occurs from reuse and sharing), Flexibility (flexible but not more flexible than RDBMS), Abstraction (permits developers of software to incorporate their individual types and techniques applied to DBMS), Relationship managing (helps in gathering records effortlessly) Object Relationship handling (can handle any every type of relationship), Use of navigational interfaces – hence better than other models QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 125268 QUESTION_TEXT Define transaction. Explain their properties. Definition – 2 marks 4 properties – 2 marks each Transaction is a logical unit of data manipulation related tasks wherein either all the component tasks must be completed or none of them is executed in order to keep the database consistent. ACID properties SCHEME OF EVALUATION Atomicity – Either every operation is executed in a successful manner or none of them is executed at all. Consistency – database integrity rules must be obeyed properly Isolation – assurance that all transactions are executed independently even in a multitransaction environment Durability – changes performed in the database are saved in physical database once the transaction is over. QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 125269 QUESTION_TEXT What is denormalization? Explain its techniques. Definition – 2 marks each SCHEME OF EVALUATION 4 techniques – 2 marks Denormalization is the process of converting higher normal norms to lower normal forms with the objective of getting faster access to database. (a) Duplicate data – method of adding duplicate data into relational table. This will minimize the number of joins required to execute a given query. It also minimizes the CPU and I/O resources being utilized as well as boosts up the performance (b) Summary data – records are summarized in some summary columns thereby reducing the number of records stored in a table. This enhances database performance as now the database server needs to process lesser records for a given query execution (c) Horizontal partitioning – table is split by rows thereby reducing the number of records paer table and hence drives the performance (d) Vertical fragmentation – breaks relations by columns. It makes more than 2 tables by allocating the original key to all and allocating a few of the non key columns to every newly made identical keyed table QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 125271 QUESTION_TEXT Differentiate between BCNF and 3 NF. Comparison of BCNF and 3NF We have seen BCNF and 3NF. It is always possible to obtain a 3NF design without sacrificing losslessjoin or dependency-preservation. If we do not eliminate all transitive dependencies, we may need to use null values to represent some of the meaningful relationships. Repetition of information occurs. SCHEME OF EVALUATION These problems can be illustrated with Banker-schema. As banker-name bname , we may want to express relationships between a banker and his or her branch. Figure : An instance of Banker-schema. Figure shows how we must either have a corresponding value for customer name, or include a null. Repetition of information also occurs. Every occurrence of the banker's name must be accompanied by the branch name. If we must choose between BCNF and dependency preservation, it is generally better to opt for 3NF. If we cannot check for dependency preservation efficiently, we either pay a high price in system performance or risk the integrity of the data. The limited amount of redundancy in 3NF is then a lesser evil. To summarize, our goal for a relational database design is BCNF. Lossless-join. Dependency-preservation. If we cannot achieve this, we accept 3NF Lossless-join. Dependency-preservation. A final point: there is a price to pay for decomposition. When we decompose a relation, we have to use natural joins or Cartesian products to put the pieces back together. This takes computational time. QUESTION_TYPE DESCRIPTIVE_QUESTION QUESTION_ID 125275 QUESTION_TEXT Discuss Semantic Query Optimization. What are the various Execution Strategies for SQL Sub Queries? SCHEME OF EVALUATION Semantic Query Execution: Semantic Query Execution is a technique to modify one query into another query by using the relational database constraints. These constraints may be unique attributes or much more complex constraints. This technique is used for the efficient execution of the query. (1 mark) Consider the example below: Select E.LNAME, M.LNAME FROM EMPLOYEE AS E, EMPLOYEE AS M WHERE E.SUPERNO=M.ENO AND E.SALARY>M.SALARY marks) (2 This query retrieves the names of employees who earn more than their supervisors. If a constraint is applied on the database schema to check that none of the employee can earn more than his reporting supervisor; the semantic query optimizer checks for this constraint and may not execute the query if it knows that the resultant query will be empty. If the constraint check is done efficiently then this approach can save a lot of time. (2 marks) Execution Strategies for SQL Sub Queries: Different physical execution strategies are employed by query optimizer for the various logical query plan options. Two types of strategies are there for sub query execution: 1. Navigational Strategies 2. Set-Oriented Processing (1 mark) 1. Navigational Strategies: For executing sub-query, navigational strategies depends on the nested loops joins. Basically there are two classes of navigational strategies: forward lookup and reverse lookup. Forward lookup firstly starts executing the outer query and when outer rows are generated then it invokes the sub-query. Reverse lookup starts with the sub-query and processes one sub-query row at a time. (2 marks) 2. Set-Oriented Processing: Set-Oriented Processing finally needs that the query could be effectively de-correlated. If this is the situation, set operations for example hash, merge and join can execute the query. (2 marks)