CDBMS 2008
THANKS TO RAHUL SINGH CHOUDHARY
PART A
Q1: Distinguish between weak entity and strong entity?
Ans: In a relational database, a Weak Entity is an entity that cannot be uniquely identified by its attributes alone; therefore, it must use a foreign key in conjunction with its attributes to create a primary key. The foreign key is typically a primary key of an entity it is related to. In entity relationship diagrams a weak entity set is indicated by a bold rectangle (the entity) connected by a bold type arrow to a bold diamond (the relationship).
Any entity which can form primary key independently called strong entity.
Difference:
A strong entity is independent of other entities and can exist on its own. A weak entity is dependent on one or more other entities in order for it to exist.
For example, a child entity is a weak entity because it relies on the parent entity in order for it to exist.
Q2: Define “Domain” with respect to relational model?
Ans: In Relational model the basic relational building block is the domain or data type, usually abbreviated nowadays to type. A tuple is an ordered set of attribute values. An attribute is an ordered pair of attribute name and type name. An attribute value is a specific valid value for the type of the attribute. This can be either a scalar value or a more complex type.
Q3: Define the basic structure in the network model?
Ans: The network model is a database model conceived as a flexible way of representing objects and their relationships. Its distinguishing feature is that the schema, viewed as a graph in which object types are nodes and relationship types are arcs, is not restricted to being a hierarchy or lattice.
Example of network model:
Q4: What is information privacy?
Ans: When people speak about database privacy, they usually are referring to the protection of information contained within digital databases and of the databases themselves. It can include security issues surrounding the database and the classification of its information. Database privacy is a concept that is important to organizations and private citizens alike. However, organizations have the responsibility to protect clients' information, because their clients entrust them to do so.
The fact that many individuals don't have control over how their information is stored and handled once it is digitally aggregated can be a source of concern. Old database storage systems were physical and had their own database privacy issues. The data storage methods of computers have presented their own unique obstacles. Computer privacy is inherently tied to the idea of database privacy because many companies and organizations now employ some sort of digital recordkeeping. Sensitive, confidential and critical information is often kept in databases. To protect this information from being accessed by third-parties without clearance, companies and organizations have to be diligent about data protection. Some of their efforts have to center on guarding against threats to application servers, database servers and storage systems.
Q5: What is the importance of knowledge?
Ans: There are following:
1. Handling of any task, process or interaction in ordinary way or extra ordinary way
2. MIS and DSS can be well guided.
3. Collection capability of an individual /work group.
4. Practice of KM enhances performance/ Productivity increase in continual manner
5. KM helps corporate in protecting its market share, build future opportunity share and stay ahead of competition.
Q6: What is data mining?
Ans: Data mining, the extraction of hidden predictive information from large databases, is a powerful new technology with great potential to help companies focus on the most important information in their data warehouses. Data mining tools predict future trends and behaviors, allowing businesses to make proactive, knowledge-driven decisions. The automated, prospective analyses offered by data mining move beyond the analyses of past events provided by retrospective tools typical of decision support systems. Data mining tools can answer business questions that traditionally were too time consuming to resolve.
Key elements:
• Massive data collection
• Powerful multiprocessor computers
• Data mining algorithms
Q7: List any two risks of database approach?
Ans:
Risks:
Legality (having to adhere to laws for keeping personal data).
Getting data wrong and seriously annoying people.
Keeping data secure so it can be stolen/changed.
Q8: What is strong entity?
Ans: Refer Ans 1.
Q9: What do understand by unary relationship set?
Ans: Unary Relationships
• The unary relationship has degree = 1.
• This is also termed a recursive relationship.
• This represents an association between occurrences of a single entity.
• Examples include the following with the cardinalities no.
o Unary PERSON 1:1 PERSON (Marriage)
o Unary EMPLOYEE 1:N EMPLOYEE (Supervise)
o Unary ITEM N:N ITEM (BillofMaterials)
Q10: Difference between Codification system and numbering system?
Ans: The Codification System (NCS for short) is a standard approach to identify, classify and number items of supply. This is applicable to items that are repetitively used and stocked (e.g., repair parts, equipment, food items, etc.). The result is a unique identification and a data set that can be easily shared and understood by a wide range of users. The process of codification (or cataloging) involves naming, classifying, describing the item.
Q11: What are the key components of information system architecture?
Ans: Consists of:
Data (e.g. Enterprise Data Model–simplified ER Diagram)
Processes–data flow diagrams, process decomposition, etc.
Data Network–topology diagram (like Fig 1-9)
People–people management using project management tools (Gantt charts, etc.)
Events and points in time (when processes are performed)
Reasons for events and rules (e.g., decision tables)
Q12: What does an attribute mean?
Ans: An attribute of an entity is a particular property that describes the entity. The set of all possible values of an attribute is the attribute domain.
Each entity has attributes, or particular properties that describe the entity. For example, student Emanuel Vagas has properties of his own Student Identification number, name, and grade. A particular value of an attribute, such as 93 for the grade, is a value of the attribute. Most of the data in a database consists of values of attributes. The set of all possible values of an attribute, such as integers from 0 to 100 for a grade, is the attribute domain.
ER diagram notation for an attribute domain (StudentGrade) of an entity type (student)
PART B
Q1: Diagrammatically brief all the components of a data base table?
Ans: It is a collection of rows and columns and made up of small entities called cells. These cells are used to store data and user information in a well structured and organized manner.
Tables, Columns and Rows
These three items form the building blocks of a database. They store the data that we want to save in our database.
Columns
Columns are akin to fields, that is, individual items of data that we wish to store. A customer's name, the price of a part, the date of an invoice is all examples of columns. They are also similar to the columns found in spreadsheets (the A, B, C etc along the top).
Rows
Rows are akin to records as they contain data of multiple columns (like the 1,2,3 etc in a spreadsheet). Unlike file records though, it is possible to extract only the columns you want to make up a row of data. Old "records" that computers read forced the computer to read EVERYTHING, even if you only wanted a tiny portion of the record. In databases, a row can be made up of as many or as few columns as you want. This makes reading data much more efficient - you fetch what you want.
Tables
A table is a logical group of columns. For example, you may have a table that stores details of customers' names and addresses. Another table would be used to store details of parts and yet another would be used for supplier's names and addresses.
It is the tables that make up the entire database and it is important that we do not duplicate data at all. Only keys would duplicate (and even then, on some tables - these would be unique).
Keys
Keys are used to relate one table for another. For example. A customer places an order for some parts. We need to store the customer's details, the parts ordered and the supplier of the parts (to ensure we have enough stock or place a new order to restock).
Q2: What is virtual organization? What are its characteristics?
Ans: virtual company, an organization that uses computer and telecommunications technologies to extend its capabilities by working routinely with employees or contractors located throughout the country or the world. Using e-mail, faxes, instant messaging, data and videoconferencing, it implies a high degree of telecommuting as well as using remote facilities. The most extreme type of virtual company is one with only "virtual employees" and no central office. Everyone works from home, including top management.
A network of people or organizations which are independents.
Those people and organizations are realizing a common project or common economic activity.
The communication and information processes are hold through information technologies.
The organization does not depend on time and space to be made up.
The figure below points up well the principal’s characteristics of the virtual organization concept.
Typology of virtual Organization
According to Mowshowith (1994) the virtualization may be taken at different level. Venkatraman (1995) and Saaksjarvi suggest several stratums in the process:
Individual level or sub-intraorganizational is regarding local tasks involving a group of people in a distinct organization via distance communication process.
Organizational level when information technologies is used to coordinate the activities of the organization as an integration.
And interoganizational level is the last layer where numerous organizations utilize the information technologies to coordinate an economic activity (see the picture below).
The virtualization process of an organization may outcome a:
Virtual team, which is the simplest form of a VO, is a local team using information technologies to coordinate their connectivity and share their knowledge at lower cost.
Virtual project can involve several people or organizations in the realization of certain task which are a beginning and designated end.
Temporarily virtual organization is likening a virtual project involving several organizations in a designated period of time.
Permanent virtual organization is created when there is no designated period in their cooperation.
Q3: Briefly explain all the stages of SDLC?
Ans:
The relationship of each stage to the others can be roughly described as a waterfall, where the outputs from a specific stage serve as the initial inputs for the following stage. During each stage, additional information is gathered or developed, combined with the inputs, and used to produce the stage deliverables. It is important to note that the additional information is restricted in scope; “new ideas” that would take the project in directions not anticipated by the initial set of high-level requirements are not incorporated into the project. Rather, ideas for new capabilities or features that are out-of-scope are preserved for later consideration.
After the project is completed, the Primary Developer Representative (PDR) and Primary End-User Representative (PER), in concert with other customer and development team personnel develop a list of recommendations for enhancement
of the current software.
These stages can be characterized and divided up in different ways, including the following[6]:
• Project planning, feasibility study: Establishes a high-level view of the intended project and determines its goals.
• Systems analysis, requirements definition: Refines project goals into defined functions and operation of the intended application. Analyzes end-user information needs.
• Systems design: Describes desired features and operations in detail, including screen layouts, business rules, process diagrams, pseudocode and other documentation.
• Implementation: The real code is written here.
• Integration and testing: Brings all the pieces together into a special testing environment, then checks for errors, bugs and interoperability.
• Acceptance, installation, deployment: The final stage of initial development, where the software is put into production and runs actual business.
• Maintenance: What happens during the rest of the software's life: changes, correction, additions, and moves to a different computing platform and more. This, the least glamorous and perhaps most important step of all, goes on seemingly forever.
Q4: What do you understand by characteristics of KM?
Ans: Knowledge Management helps organizations
• Identify
• Select
• Organize
• Disseminate
• Transfer
Important information and expertise within the organizational memory in an unstructured manner.
It requires a major transformation in organizational culture to create a desire to share.
• Knowledge as a form of capital, must be exchangeable among persons, and must be able to grow.
• Knowledge is information that is contextual, relevant and actionable.
• Knowledge is information in action.
• It is higher than data and information.
Knowledge Management Characteristics:
The challenge of Knowledge Management is to determine what information within an organization qualifies as"valuable."All information is not knowledge, and all knowledge is not valuable. The key is to find the worthwhile knowledge within a vast sea of information.
1. Knowledge Management is about people.It is directly linked to what people know, and how what they know can support business and organizational objectives. It draws on human competency, intuition, ideas, and motivations. It is not a technology-based concept. Although technology can support a Knowledge Management effort, it shouldn’t begin there.
2. Knowledge Management is orderly and goal-directed.It is inextricably tied to the strategic objectives of the organization. It uses only the information that is the most meaningful, practical, and purposeful.
3. Knowledge Management is ever-changing.There is no such thing as an immutable law in Knowledge Management. Knowledge is constantly tested, updated, revised, and sometimes even"obsoleted"when it is no longer practicable. It is a fluid, ongoing process.
4. Knowledge Management is value-added.It draws upon pooled expertise, relationships, and alliances. Organizations can further the two-way exchange of ideas by bringing in experts from the field to advise or educate managers on recent trends and developments. Forums, councils, and boards can be instrumental in creating common ground and organizational cohesiveness.
5. Knowledge Management is visionary.This vision is expressed in strategic business terms rather than technical terms, and in a manner that generates enthusiasm, buy-in, and motivates managers to work together toward reaching common goals.
6. Knowledge Management is complementary.It can be integrated with other organizational learning initiatives such as Total Quality Management (TQM). It is important for knowledge managers to show interim successes along with progress made on more protracted efforts such as multiyear systems developments infrastructure, or enterprise architecture projects.
Q5: Explain the concept of data abstraction?
Ans: Data Abstraction
1. The major purpose of a database system is to provide users with an abstract view of the system.
The system hides certain details of how data is stored and created and maintained
Complexity should be hidden from database users.
2. There are several levels of abstraction:
1. Physical Level:
How the data are stored.
E.g. index, B-tree, hashing.
Lowest level of abstraction.
Complex low-level structures described in detail.
2. Conceptual Level:
Next highest level of abstraction.
Describes what data are stored.
Describes the relationships among data.
Database administrator level.
3. View Level:
Highest level.
Describes part of the database for a particular group of users.
Can be many different views of a database.
E.g. tellers in a bank get a view of customer accounts, but not of payroll data.
Fig. 1.1 (figure 1.1 in the text) illustrates the three levels.
Figure 1.1: The three levels of data abstraction
Q6: Super type and Sub type?
Ans: Supertypes and Subtypes
Two entities are of distinct types if they have no attributes in common. It is possible for entities to have both common and distinct attributes. If they have a common identifier (that is, a common primary key), they have a special supertype-subtype relationship: they are neither distinct nor the same. You use supertypes and subtypes to represent different levels of entity generalization. Normalization and denormalization are about breaking down and assembling. Supertyping and subtyping are about generalization and specialization. Think of normalization as widening and subtyping as deepening. When you analyze your business problem, the verb is usually leads to a supertype/subtype relationship. For example, a company is a customer, and a person is a customer as well. Obviously, companies and persons have something in common.
In the companies/persons example, you started with a bottom-up approach. You can continue this generalization further. For example, both customers and suppliers are partners. You could also start from the top and discover specializations. The question is where to stop with this process. It is easy to find where to stop when you use the top-down approach: specialization makes sense only if subtypes have additional attributes. With the bottom-up approach, you could finish with just a few entities—for example, with subjects, objects, and events. Theoretically, you should stop when you reach abstract objects, objects that do not exist in the real world. For example, a computer table is a table, and a table is furniture; however, when you come to a store, you do not order “a piece of furniture.” Still, sometimes it is good to have a supertype just to share common identification (that is, a common primary key). This enables you to gather all the information for a supertype for advanced analysis. A practical approach is to stop when you have a problem naming the supertype. If you cannot name it quickly, probably nobody would need to perform analysis on that supertype.
If you overlooked supertypes and subtypes when you analyzed your business problem or if you are working on refining an existing model, you can still identify them from the existing model. A huge table with sparse known values and many NULL values is a candidate for specialization. Check whether those unknown values are really unknown or whether they are simply meaningless for some rows. If they are meaningless, you can get rid of them when you introduce subtypes. Using the bottom-up approach from an existing model is possible only if the model stays with a naming convention; otherwise, you have to re-analyze the business problem. Tables that have many columns with similar or even the same names probably need a supertype table.
Q7: What is encryption?
Ans: Encryption is the process used to hide our data, or the contents of a message, from prying eyes throughout the internet. During transmission (such as through a secure socket layer), the data is disguised using codes so that no one along the chain of networks that the data passes though to get to its source can understand the information being sent. When the data arrives at its destination, it is decrypted to reveal the information being transmitted.
The process of disguising the data is called encryption and the process of revealing the data from its encrypted form is called decryption. Both of these are common techniques used in cryptography - the scientific discipline behind secure connections. The processes are done using mathematical logic, or algorithms.
Q8: Define the basic structure in the network model?
Ans: Networking Model
The International Standards Organization (ISO) has defined a standard called the Open Systems Interconnection (OSI) reference model. This is a seven layer architecture listed below. Each layer is considered to be responsible for a different part of the communications. This concept was developed to accommodate changes in technology. The layers are arranged here from the lower levels starting with the physical (hardware) to the higher levels.
1. Physical Layer - The actual hardware. Concerned with the connection between the computer and the network.
2. Data Link Layer - Data transfer method (802x ethernet). Puts data in frames and ensures error free transmission. Also controls the timing of the network transmission. IEEE divided this layer into the two following sublayers.
1. Media Access Control (MAC) - Used to coordinate the sending of data between computers. The 802.3, 4, 5, and 12 standards apply to this layer. If you hear someone talking about the MAC address of a network card, they are referring to the hardware address of the card.
2. Logical Link control (LLC) - Maintains the Link between two computers by establishing Service Access Points (SAPs) which are a series of interface points. IEEE802.2.
3. Network Layer - IP network protocol. Routes messages using the best path available. Concerned with message priority, status, and data congestion.
4. Transport Layer - TCP, UDP. Provides properly sequenced and error free transmission. Recombines fragmented packets.
5. Session Layer - Determines when the session is begun or opened, how long it is used, and when it is closed. concerned with security and name recognition.
6. Presentation Layer - ASCII or EBCDEC data syntax. Makes the type of data transparent to the layers around it. Used to translate date to computer specific format such as byte ordering. It may include compression. It prepares the data, either for the network or the application depending on the direction it is going.
7. Application Layer - Provides the ability for user applications to interact with the network.
PART C
Q1.Steps involved setting up information system in organization?
Ans: There are following steps:
Information Systems Planning
Purpose–align information technology with organization’s business strategies
Three steps:
1. Identify strategic planning factors
• Organization goals–what we hope to accomplish
• Critical success factors–what MUST work in order for us to survive
• Problem areas–weaknesses we now have
2. Identify corporate planning objects
• Organizational units–departments
• Organizational locations
• Business functions–groups of business processes
• Entity types–the things we are trying to model for the database
• Information systems–application programs
3. Develop enterprise model
• Functional decomposition
Iterative process breaking system description into finer and finer detail
• Enterprise data model
• Planning matrixes
Describe interrelationships between planning objects
Q2. Role of DBMS?
Ans: Refer SOLVED PAPER 2009 and also following roles of DBMS:
Without a database management system organizing, controlling and cataloging data, an information system would be an organized conglomeration of data. The ultimate role of a database management system is to implement controls and provide maintenance to data files using data security to ensure integrity of data.
Cataloging of File Structures
1. The process of cataloging files in a database management system (DBMS) is extremely important. There are various file types, which range from actual computer code and query programs (which extract information) to system utility and record maintenance programs. All of these programs have a unique file structure, which is identified by a system schematic or "schema." Without the process of a file structure, files would be hard to access and operate. A file structure within a (DBMS) provides an orderly structure for file access and management.
Identification of Database Types
2. A DBMS system can consist of various database types. A database holds the record structure of information. Databases within a DBMS can be an indexed, sequential or relational database. An index database is based on a primary key and can be indexed on any unique field within the database structure. A sequential database is accessed by starting at the very first record in the database and a relational database consists of records, which can be joined to other existing records in another database based on unique identifiers. The DBMS allows for partitioning, cataloging and access for these database types.
Data Security
3. Data security is an important feature for any information system. A DBMS provides security tables, which are records designated for user information, identification and passwords. The security system is constructed from relational database tables and each condition (user access codes) must be met in each table for a user to access the system. DBMS systems can have built-in security applications, which assign user rights and privileges by using a table of authorities in the system utility applications.
Tables and Records
4. Within a DBMS, all databases have assigned records. Records are classified as item or detail records. Item records are general information records and detail records focus on a field identifier within the item record and provide extra "detailed" information on the field and generated its record from the item record. Tables are structures on which item and detail records exist. An example of an item and detail record is a description of furniture on a database consisting of general data fields for shipping, payment, etc., and a corresponding detail record, which further breaks down the furniture into various colors.
Integrity of Data Sets
5. If an information system is a transaction based processing system, data sets are created to catalog changes in data initiated by users to the system with all changes reporting on a transaction exception report. Data is collected, distributed and processed using batch or real-time methods. If it is a batch routine, most organizations will update their systems once a day while, with a real-time system, updates can be added immediately.
Q3. Advantages of DBMS over traditional file system?
Ans: Explain the followings:
• Program-data independence.
• Planned data redundancy.
• Improved data consistency.
• Improved data sharing.
• Increased application development productivity.
• Enforcement of standards.
• Improved data quality.
• Improved data accessibility and responsiveness.
• Reduced Program maintenance.
• Improved Decision support.
Good Luck.
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