DATABASE DEVELOPMENT (H4)

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1 IMIS HIGHER DIPLOMA QUALIFICATIONS DATABASE DEVELOPMENT (H4) December :00hrs 13:00hrs DURATION: 3 HOURS Candidates should answer ALL the questions in Part A and THREE of the five questions in Part B. Part A carries 40% of the marks available and Part B carries 60%. Candidates should allocate their time accordingly. No reference material of any kind may be taken into the examination. [Turn over] Page 1 of 10

2 PART A. Answer ALL questions in this section Question A1 (AC1.3) Describe what is meant by logical data independence. Data independence is an objective of the three-level ANSI-SPARC architecture and means that changes in one level do not affect another. Logical data independence means that changes to the conceptual schema can be done without affecting the external schema, or application program. For example, adding or removing entities, attributes or relationships Question A2 (AC2.2) Describe the key components of a conceptual model you are familiar with. Include a brief diagram to illustrate the model chosen. There are different types of conceptual model, one likely choice is an entityrelationship diagram. For this the key components would be the entities, relationships and attributes. for an appropriate diagram. Alternative conceptual models are acceptable. Question A3 (AC3.1 and 3.2) Structured Query Language (SQL) commands can be categorised as Data Manipulation Language (DML) or Data Definition Language (DDL) commands. Using examples, explain the difference between DML and DDL commands. DDL commands define the structure of the database objects, including CREATE, DROP or ALTER commands, such as CREATE TABLE. Whilst DML commands manipulate or alter the data, DML commands include INSERT, UPDATE, SELECT and DELETE commands Question A4 (AC4.2) Indexes are an important technique to aid SQL performance, describe two situations where an index should be used and one situation where they would not be helpful. T2 lists guidelines on where indexes would be useful:. - Create an index for single columns used in a WHERE, HAVING, ORDER BY or GROUP BY clause; - Create an index when the values are relatively unique in the column, or a wide range of values; - Where a MIN/MAX function is applied on a column; - For primary and foreign key columns; - For any join columns, other than the primary/foreign keys Page 2 of 10

3 Indexes should not be used if functions other than MIN/MAX are used, or there is a small range of values. Other appropriate reasons are acceptable. Up to marks per point, up to maximum of 5 marks Question A5 (AC5.2) Describe two main advantages of using a distributed database management system. T1 gives the following advantages: - Reflects organisational structure many organisations are naturally distributed; - Improved shareability and local autonomy geographical distribution of a company can be reflected in the DDBMS; - Improved reliability data can be replicated so a failure somewhere does not mean the data is inaccessible; - Improved availability failure in one site does not mean the whole DBMS is not working. Failure of a single node can mean requests can be rerouted to another side; - Improved performance data should be located at site of greatest demand, so each site should mainly handle part of the data; - Economics should be more cost effective; - Modular growth potential easier to handle expansion in a DDBMS; - Integration of legacy systems integrate existing data to coexist with newer systems. Or any other valid points are acceptable. per point, plus up to for the description Question A6 (AC6.2) Briefly explain what takes place during the Extraction step of the Extraction, Transformation and Loading (ETL) process of a data warehouse. T1 explains that the Extraction step consists of: - One or more data sources are targeted for the Enterprise Data Warehouse (EDW); - These sources are generally OLTP databases, but can also be personal databases or spreadsheets, or other sources such as web usage log files; - The data sources are generally internal, but could be external, such as supplier information; - The complexity of the extraction depends on how similar the data sources are, or availability of the documentation; - Some cleaning may be needed to ensure all the data follows the same format. per point, up to a maximum of 5. Other relevant points are acceptable Page 3 of 10

4 Question A7 (AC2.1) In the database systems development lifecycle describe what steps can be taken to determine the user requirements. An initial study should be carried out, the analysis stage should use this to identify constraints on the data, objectives of the new system system designers need to work with users to identify processes and potential problems. Other relevant points accepted. Question A8 (AC6.1) Describe TWO problems that can occur with developing and managing a data warehouse. T1 identifies the following problems: Underestimation of resources: developers underestimate the time required to extract, transform and load data; ETL process can account for a lot of the total development time; Hidden problems with source systems: can be problems with the systems feeding the warehouse; does the developer fix the problem in the data warehouse, or the source system? Required data not captured: existing systems may not have the data required; does the developer add this to the OLTP system, or the data warehouse (DW)? Data homogenization: large-scale data warehousing can lead to data homogenization, which can lessen the value of the data; Data ownership: a data warehouse can change attitude of end-users to the ownership of the data; data that was once sensitive can now be seen by others in the DW. High demand for resources: the DW can use a lot of disk space; number crunching type applications can also slow the system down; Long duration projects: building a DW can take several years to become effective; some organisations try a data mart first; Complexity of integration: integrating data from several sources is not a trivial exercise. Tools can help, but need to integrate well to make the DW beneficial. per problem identified and up to marks per problem for the discussion. PART B. Answer any THREE of the following FIVE questions. Question B9 (AC1.4) A University is developing a new Student Information System, describe the role of the following in developing the system: Page 4 of 10

5 a) Data administrator b) Database Designer c) Application Developers d) End-users Data administrator (DA) - Responsible for management of the data; - Includes planning, development, policies and procedures; - Responsible for the conceptual and logical design; (Total 20 marks) - Should ensure the database system fulfil the requirements of the University - Needs to ensure legal requirements are covered, such as the UK Data Protection Act. Database designer - Can be two types: logical and physical designers; - Logical concerned with identifying the data requirements, defining the entities, relationships, business rules; - Will produce conceptual and logical designs, such an ER diagram and the mapping to relational tables; - Physical designer concerned with how logical design is physically realised, such as creating the tables and any constraints; - Would include any security and performance features, such as indexes; - They would be key to designing the Student System. Application developers - The student system is not just about the database system; - The developers are responsible for developing the application programs that provide the functionality; - They work to the specification typically produced by the systems analysts; - The application programs are needed to perform some operation on the database, such as retrieving or updating the database; - The programs can be written in a third-generation language, such as C, fourth-generation language that may have been provided by the vendor, or a scripting language such as PHP. End users - These are the users of the database systems developed; - Can be two types: naïve and sophisticated; Page 5 of 10

6 - Naïve could be the student users with little technical skills and sophisticated could be non-database staff working for the University, such as the administrators. Both could be consulted for the requirements for the new system. 5 marks each per point, up to 5. Should include examples specific to a University for full marks Question B10 a) Describe what are the key features of the following data models: i. Hierarchical and network model ii. Relational model iii. Object oriented model (15 marks) b) Describe, with examples, two advantages of one of the above data models. a) T1 highlights the following points: i. Hierarchical and network model - older type of data model; - difficult to represent M:N relationships; - record-at-a time processing; - low data independence; - access path predefined (navigational access) ii. relational model - available since the 1970s; - mathematical basis (set based); - provides data independence; - allows ad-hoc queries using SQL iii. object oriented model - popular from mid-1980s; - provides more semantics in the data model; - provides support for complex objects; - allows inheritance; - includes behaviour (Total 20 marks) per point, up to 5 maximum per data model. Other appropriate points are acceptable. b) Advantages can include: i. Hierarchical and network model - Parent/child relationships provide conceptual simplicity; Page 6 of 10

7 - Efficient with 1:M relationships; - Database security is enforced by the DBMS ii. relational model - conceptual simplicity; - handles more relationship types, such as M:Ns; - conformance to standards; - includes a DDL and DML iii. object oriented model - semantic content is added; - inheritance promotes data integrity; - allows functionality to be stored in the database per point, up to 5 maximum. Other appropriate points are acceptable. Question B11 (AC3.1) Given the following tables that represents part of a sales order system: Order Column name Data type Constraints/Comments OrderNo NUMBER(8) Primary key OrderDate DATE Date the order was made DeliveryDate DATE Date the order is delivered, it must be the same or later than the OrderDate CourierRef VARCHAR(20) A unique reference number provided by the courier for the delivery. TotalCost NUMBER(7,2) Total cost of the order. A business rule that states an order cannot be for less than 50. Order Line (an order can be for many items) Column name Data type Constraints/Comments OrderNo NUMBER(8) Part of a composite primary key; A foreign key to Order ItemNo NUMBER(5) Part of a composite primary key Quantity NUMBER(3) The number of items ordered. This is a number between 1 and 100 a) Write SQL code to create the ORDER table, including all constraints identified. (10 marks) b) Write SQL code to create the ORDER_LINE table, including all constraints identified. (8 marks) c) Most database management systems will create an index automatically on the primary key field, pick one other field that could benefit from an index, explaining why. (2 marks) Page 7 of 10

8 (Total 20 marks) a) CREATE TABLE ORDER ( OrderNo NUMBER(8) PRIMARY KEY, OrderDate DATE, for rest of the columns DeliveryDate DATE, CONSTRAINT chk_date CHECK (OrderDate <= DeliveryDate), CourierRef VARCHAR(20) UNIQUE, TotalCost NUMBER (7,2) CONSTRAINT chk_cost CHECK (TotalCost > 50)) ; b) CREATE TABLE ORDER_LINE ( OrderNo NUMBER(8), for rest of columns ItemNo NUMBER(5), Quantity NUMBER(3) Quantity NUMBER(3) constraint chk_qty CHECK (quantity BETWEEN 1 and 100), PRIMARY KEY (OrderNo, ItemNo), FOREIGN KEY (OrderNo) REFERENCES ORDER (OrderNo) ); c) Possible fields include: - OrderNo in ORDER_LINE (foreign key is likely to be joined often) - CourierRef (unique field, could be queried often) - OrderDate or DeliveryDate (the dates could be queried often) for choice of appropriate field and for justification. Question B12 (AC5.3) There are different approaches to fragmentation in a distributed database, using suitable examples to illustrate your answer: a) Explain why fragmentation is needed b) Describe two main types of fragmentation c) Discuss what problems can occur from fragmentation 10 marks) a) T1 gives 4 reasons for fragmentation: (Total 20 marks) - Usage: most applications work with views rather than the whole relation so appropriate to work with subsets of the data; - Efficiency: data is stored to where it is most used; - Parallelism: fragmentation can increase the degree of concurrency; Page 8 of 10

9 - Security: data not required by a local application is not stored there for reason and for description, up to 5 marks. b) There are two main types of fragmentation: vertical and horizontal: - Vertical fragmentation consists of a subset of the attributes in a relation - The subset should contain the primary key so that the original relation can be reconstructed - Means that the fragments can be stored at the sites that need them - An example could be an Employee table, where only the salary and commission details are stored in the HR department. - Horizontal fragmentation consists of a subset of the tuples in a relation - The subset will be based on a predicate that produces a restriction on the tuples - The restriction will group tuples that have some common properties - The complete relation can be reconstructed using a Union operation - For example, in a large organisation, the employees could be fragmented by location c) Disadvantages can include: - Performance : if a global application requires data from several sites, performance can be slower ; - Integrity : control can be harder, for example, ensuring there are not duplication primary keys created over several sites or functional dependencies are fragmented and located at different sites - Other appropriate points are acceptable. Question B13 (AC6.3) Describe the following data mining operations and give an example of an application of where they can be used: a) Predictive modeling b) Database segmentation c) Link analysis d) Deviation Detection (Total 20 marks) Page 9 of 10

10 a) Predictive modeling - Similar to human learning - Generalises real world - Analyses a database to determine characteristics of the data - Application: customer retention management b) Database segmentation - Aim to partition database into segments of similar records - Uses unsupervised learning to look for sub-populations in the database - Used for customer profiling and direct marketing Application: Demographic clustering or neural clustering used to calculate distance between records c) Link analysis - Looks to establish links in the records - For example, stock market movement - Three types of techniques: o associations (find items that imply presence of something else), o sequential pattern (find patterns between events that follow each other) o similar time sequence discovery (find patterns that are time dependent, e.g., buying a house, then new cooker, etc.) - Application: direct marketing d) Deviation Detection - Looks for outliers in data - Picks up deviations from previous expectation - Application: credit card fraud detection for each point, up to maximum of 4 per operation, for an appropriate application. Other appropriate points are acceptable. END OF EXAMINATION Page 10 of 10

Database Development (H4)

IMIS HIGHER DIPLOMA QUALIFICATIONS Database Development (H4) Thursday 30 th November 2017 10:00hrs 13:00hrs DURATION: 3 HOURS Candidates should answer ALL EIGHT questions in Part A and THREE of the FIVE