(Solution Manual) Database Systems A Practical Approach to Design, Implementation, and Management

Connolly, Begg, 6

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Author(s): Connolly, Begg

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Database Systems: Instructor’s Guide - Part III 3 Chapter 1 Introducti on to Databases Review Questions 1.1 List four examples of database systems other than those listed in Section 1.1. Some examples could be: • A system that maintains component part details for a car manufacturer; • An advertising company keeping details of all clients and adverts placed with them; • A training company keeping course information and participants’ details; • An organization maintaining all sales order information. 1.2 Discuss each of the following terms: Data For end users, this constitutes all the different values connected with the various objects/entities that are of concern to them. See also Section 1.3.4. Database See Section 1.3.1 Database Management System See Section 1.3.2 Database Application Program See Section 1.3.3 Data Inde pendence This is essentially the separation of underlying file structures from the programs that operate on them, also called program -data independence. See also Sections 1.2.2 and 1.3.1. Security The protection of the database from unauthorized users, w hich may involve passwords and access restrictions. See also Section 1.6. Integrity The maintenance of the validity and consistency of the database by use of particular constraints that are applied to the data. See also Section 1.6. Views These present only a subset of the database that is of particular interest to a user. Views can be customized, for example, field names may change, and they also provide a level of security preventing users from seeing certain data. See also Section 1.3.3. 1.3 Describ e the approach taken to the handling of data in the early file -based systems. Discuss the disadvantages of this approach. Focus was on applications for which programs would be written, and all the data required would be stored in a file o r files owned by the programs. See also Section 1.2. Clearly, each program was responsible for only its own data, which could be repeated in other program’s data files. Different programs could be written in different languages, and would not be able to access another p rogram’s files. This would be true even for those programs written in the same language, because a program needs to know the file structure befo re it can access it. See also Section 1.2.2 . 1.4 Describe the main characteristics of the database approach and contrast it with the file -based approach. Database Systems: Instructor’s Guide - Part III 4 Focus is now on the data first, and then the applications. The structure of the data is now kept separate from the programs that operate on the data. This is held in the system catalog or data dictionary. Progra ms can now share data, which is no longer fragmented. There is also a reduction in redundancy, and achievement of program -data independence. See also Section 1.3. 1.5 Describe the five components of the DBMS environment and discuss how they relate to each other. See Section 1.3.3. 1.6 Discuss the roles of the following personnel in the database environment: Data Administrator See Section 1.4.1 Database Administrator See Section 1.4.1 Logical Database Designer See Section 1.4.2 Physical Database Designer See Section 1.4.2 Application Developer See Section 1.4.3 End-Users See Section 1.4.4 1.7 Discuss the three generations of DBMSs. The CODASYL and hierarchical approaches represented the first generation of DBMSs. Th ey were based on the con cept that smaller components come together as parts of larger components, and so on, until the final product is assembled. This structu re, which conforms to an upside down tree, is also known as a hierarchical structure . Relational DBMSs are referred to a s second -generation DBMSs. In 1970, E. F. Codd of the IBM Research Laboratory produced his highly influential paper on the relational data model (“A relational model of data for large shared data banks,” Codd, 1970). This paper was very timely and addresse d the disadvantages of the former approaches. Many experimental relational DBMSs were implemented thereafter . In response to the increasing complexity of database applications, two “new” systems have emerged: the object -oriented DBMS (OODBMS ) and the object-relational DBMS (ORDBMS ). However, unlike previous models, the actual composition of these models is not clear. This evolution represents third generation DBMSs . 1.8 Discuss the advantages and disadvantages of database management systems. See Section 1.6 Database Systems: Instructor’s Guide - Part III 5 Exercises 1.9 Interview some users of database systems. Which DBMS features do they find most useful and why? Which DBMS facilities do they find least useful and why? What do these users perceive to be the advantages and disadvantages of the DBMS? Select a variety of users for a particular DBMS. If the users are using different DBMSs, group the answers for the different systems, which will give an overall picture of specific systems. 1.10 Write a small program (using pseudocode, if necessary) tha t allows entry and display of client details including a client number, name, address, telephone number, preferred number of rooms, and maximum rent. The details should be stored in a file. Enter a few records and display the details. Now repeat this proce ss but rather than writing a special program, use any DBMS that you have access to. What can you conclude from these two approaches? The program can be written in any appropriate programming language, such as Pascal, FORTRAN, C. It should adhere to basic software engineering principles including being well - structured, modular, and suitably commented. It is important to appreciate the process involved even in developing a small program such as this. The DBMS facilities to structure, store, and retrieve dat a are used to the same effect. The differences in the approaches, such as the effort involved, potential for extension, ability to share the data should be noted. 1.11 Study the DreamHome case study presented in Section 10.4 and Appendix A. In what ways w ould a DBMS help this organization? What data can you identify that needs to be represented in the database? What relationships exist between the data? What queries do you think are required? It may be useful to review the file -based approach and the dat abase approach here before tackling the first part of the exercise. Careful reading and thinking about how people might use the applications should help in carrying out the rest of the exercise. 1.12 Study the Wellmeadows Hospital case study presented in Appendix B.3. In what ways would a DBMS help this organization? What data can you identify that needs to be represented in the database? What relationships exist between the data? The approach used for Exercise 1.10 should be used for this exercise also . 1.13 Discuss what you consider to be the three most important advantages for the use of a DBMS for a company like DreamHome and provide a justification for your selection. Discuss what you consider to be the three most important disadvantages for the u se of a DBMS for a company like DreamHome and provide a justification for your selection. Students should review section 1.6 to make a list of advantages and disadvant ages of using a DBMS. 1.14 Using any Web browser, look at some of the following Web pag es and discover the wealth of information available there: Database Systems: Instructor’s Guide - Part III 6 (a) http://www.oracle.com (b) http://www.microsoft.com/sql and http://www.microsoft.com/access (c) http://www.ibm.com/db2 (d) http://www.mysql.com (e) http://en.wikipedia.org/wiki/database and http://en.wikipedia.org/wiki/DBMS Students should visit the Web pages listed above to gain understanding about the type of information covered on each Web site. Pages are the major database vendor Web sites while the final two links provide information on dat abases and DBMS. Database Systems: Instructor’s Guide - Part III 7 Chapter 2 Database Environment Review Questions 2.1 Discuss the concept of data independence and explain its importance in a database environment. See Section 2.1.5 2.2 To address the issue of data independence, the ANSI -SPARC three -level architecture was proposed. Compare and contrast the three levels of this model. See Section 2.1 2.3 What is a data model? Discuss the main types of data models. An integrated collection of concepts for describing and manipulating data, relation ships between data, and constraints o n the data in an organization. See Section 2.3 . Object -based data models such as the Entity -Relationship model (see Section 2.3.1). Record - based data models such as the relational data model, network data model, and h ierarchical data model (see Section 2.3.2). Physical data models describe how data is stored in the computer (see Section 2.3.3). 2.4 Discuss the function and importance of conceptual modeling. See Section 2.3.4. 2.5 Describe the types of facility you would expect to be provided in a multi -user DBMS. Data Storage, Retrieval and Update Authorization Services A User -Accessible Catalog Support for Data Communication Transaction Support Integrity Services Concurrency Control Services Services to Promote Data Independence Recovery Services Utility Services See also Section 2.4 2.6 Of the facilities described in your answer to Question 2.5 , which ones do you think would not be needed in a standalone PC DBMS? Provide justification for your answ er. Concurrency Control Services - only single user. Authorization Services - only single user, but may be needed if different individuals are to use the DBMS at different times. Utility Services - limited in scope. Support for Data Communication - only standalone system. Database Systems: Instructor’s Guide - Part III 8 2.7 Discuss the function and importance of the system catalog . See Section 2.4 , Service (2) – User-accessible catalog. 2.8 Discuss the differences between DDL and DML? What operations would you typically expect to be available in each language? DDL - A language that allows the DBA or user to describe and name the entities, attributes, and relationships required for the application, together with any associated integrity and security constraints. DML - A language that provides a set of operations to support the basic data manipulation operations on the data held in the database. See Section 2.2.2. 2.9 Discuss the differences between procedural DMLs and nonprocedural DMLs? Procedural DML - A language that allows the user to te ll the system what data is needed and exactly how to retrieve the data. Nonprocedural DML - A language that allows the user to state what data is needed rather than how it is to be retrieved. See Section 2.2.2. 2.10 Name four object -based data models. • Entity -Relationship (ER) • Semantic • Functional • Object -oriented . See Section 2.3.1. 2.11 Name three record -based data models. Discuss the main differences between these data models. • relational data model - data and relationships are represented as table s, each of which has a number of columns with a unique name • network data model - data is represented as collections of records , and relationships are represented by sets. Compared with the relational model, relationships are explicitly modeled by the sets , which become pointers in the implementation. The records are organized as generalized graph structures with records appearing as nodes (also called segments ) and sets as edges in the graph Database Systems: Instructor’s Guide - Part III 9 • hierarchical data model - restricted type of network model. Again , data is represented as collections of records and relationships are represented by sets. However, the hierarchical model allows a node to have only one parent. A hierarchical model can be represented as a tree graph, with records appearing as nodes (also called segments ) and sets as edges . See Section 2.3.2. 2.12 What is a transaction. Give an example of a transaction. A transaction is a series of actions, carried out by a single user or application program, which accesses or changes the contents of t he database . See Section 2.4. 2.13 What is concurrency control and why does a DBMS need a concurrency control facility? A mechanism to ensure that the database is updated correctly when multiple users are updating the database concurrently. This avoid s inconsistencies from arising when two or more transactions are executing and at least one is updating the database. See Section 2.4. 2.14 Define the term "database integrity". How does database integrity differ from database security ? “Database integ rity” refers to the correctness and consistency of stored data: it can be considered as another type of database protection. Although integrity is related to security, it has wider implications: integrity is concerned with the quality of data itself. Integ rity is usually expressed in terms of constraints , which are consistency rules that the database is not permitted to violate. See Section 2.4. Exercises 2.15 Analyze the DBMSs that you are currently using. Determine each system’s compliance with the functions that we would expect to be provided by a DBMS. What type of language does each system provide? What type of architecture does each DBMS use? Check the accessibility and extensibility of the system catalog . Is it possible to export the system catalo g to another system? To do this you will need to obtain appropriate information about each system. There should be manuals available or possibly someone in charge of each system who could supply the necessary information. Database Systems: Instructor’s Guide - Part III 10 2.16 Write a program that store s names and telephone numbers in a database. Write another program that stores names and addresses in a database. Modify the programs to use external, conceptual, and internal schemas. What are the advantages and disadvantages of this modification? The p rograms can be written in any suitable language and should be well structured and appropriately commented. Two distinct files result. The structures can be combined into one containing name, address, and telNo, which can be the representation of both the i nternal and conceptual schemas. The conceptual schema should be created separately with a routine to map the conceptual to the internal schema. The two external schemas also must be created separately with routines to map the data between the external and the conceptual schema. The two programs should then use the appropriate external schema and routines. 2.17 Write a program that stores names and dates of birth in a database. Extend the program so that it stores the format of the data in the database; in other words, create a system catalog . Provide an interface that makes this system catalog accessible to external users. Again, the program can be written in any suitable language. It should then be modified to add the data format to the original file. T his should not be difficult, if the original program is well structured. The interface for other users operates on the data dictionary and is separate from the original program. A menu -based interface is adequate. Database Systems: Instructor’s Guide - Part III 11 Chapter 3 Database Architecture s and the Web Review Questions 3.1 What is meant by the term ‘client -server architecture’ and what are the advantages of this approach? Compare the client -server architecture with two other architectures. The client is a process that requires some reso urce, and the server provides the resource. Neither need reside on the same machine. Advantages include: • Better performance • Likely reduction in hardware costs • Reduction in communication costs • Better consistency See also Section 3.1. 3.2 Compare and con trast the two -tier client -server architecture for traditional DBMSs with the three -tier client -server architecture. Why is the latter architecture more appropriate for the Web? See Figures 3.5 and 3.6. Architecture maps quite naturally to the Web with a W eb browser acting as ‘thin’ client and Web server acting as an application server (with database server as third layer). 3.3 What is an n-tier architecture? The three -tier architecture can be expanded to n tiers, with additional tiers providing more flexibility and scalability. 3.4 What is middleware? Provide a classification service for middleware. Middleware is a generic term used to describe software that mediates with other software and allows for communication between disparate applications in a heterogeneous system. The need for middleware arises when distributed systems become too complex to manage efficiently without a common interface. The need to make heterogeneous systems work efficiently across a network and be flexible enough to incorporat e frequent modifications led to the development of middleware, which hides the underlying complexity of distributed systems. 3.5 What is a TP Monitor? What advantages does a TP Monitor bring to an OLTP environment? A TP Monitor forms the middle tier of a three -tier architecture. TP Monitors provide significant advantages, including: • Transaction routing: The TP Monitor can increase scalability by directing transactions to specific DBMSs. • Managing distributed transactions: The TP Monitor can manage transa ctions that require access to data held in multiple, possibly heterogeneous, DBMSs. For example, a transaction Database Systems: Instructor’s Guide - Part III 12 may require to update data items held in an Oracle DBMS at site 1, an Informix DBMS at site 2, and an IMS DBMS as site 3. TP Monitors normally co ntrol transactions using the X/Open Distributed Transaction Processing (DTP) standard. A DBMS that supports this standard can function as a resource manager under the control of a TP Monitor acting as a transaction manager. • Load balancing: The TP Monitor can balance client requests across multiple DBMSs on one or more computers by directing client service calls to the least loaded server. In addition, it can dynamically bring in additional DBMSs as required to provide the necessary performance. • Funneling: In environments with a large number of users, it may sometimes be difficult for all users to be logged on simultaneously to the DBMS. In many cases, we would find that users generally do not need continuous access to the DBMS. Instead of each user connecti ng to the DBMS, the TP Monitor can establish connections with the DBMSs as and when required, and can funnel user requests through these connections. This allows a larger number of users to access the available DBMSs with a potentially much smaller number of connections, which in turn would mean less resource usage. • Increased reliability: The TP Monitor acts as a transaction manager , performing the necessary actions to maintain the consistency of the database, with the DBMS acting as a resource manager. If the DBMS fails, the TP Monitor may be able to resubmit the transaction to another DBMS or can hold the transaction until the DBMS becomes available again. 3.6 What is a Web service? Web services allow applications to integrate with other applications ac ross the Internet and may be a key technology that supports B2B (Business to Business) interaction. Unlike other Web - based applications, Web services have no user interface and are not aimed at Web browsers. Web services instead share business logic, data, and processes through a programmatic interface across a network. In this way, it is the applications that interface and not the users. Developers can then add the Web service to a Web page (or an executable program) to offer specific functionality to users. 3.7 What technologies and standards are used to develop Web services and how do they relate to each other? Key to the Web services approach is the use of widely accepted technologies and standards, such as: • XML (extensible Markup Language). • SOAP (Sim ple Object Access Protocol) is a communication protocol for exchanging structured information over the Internet and uses a message format based on XML. It is both platform - and language -independent. • WSDL (Web Services Description Language) protocol, again based on XML, is used to describe and locate a Web service. • UDDI (Universal Discovery, Description, and Integration) protocol is a platform - independent, XML -based registry for businesses to list themselves on the Internet. It was designed to be interrogate d by SOAP messages and to provide access to WSDL documents Database Systems: Instructor’s Guide - Part III 13 describing the protocol bindings and message formats required to interact with the Web services listed in its directory. Figure 3.9 illustrates the relationship between these technologies. From th e database perspective, Web services can be used both from within the database (to invoke an external Web service as a consumer) and the Web service itself can access its own database (as a provider) to maintain the data required to provide the requested s ervice. 3.8 What is a service -oriented architecture? The SOA approach attempts to design loosely coupled and autonomous services that can be combined to provide flexible composite business processes and applications. SOA principles provide a unique desi gn approach for building Web services for SOA: • loose coupling: services must be designed to interact on a loosely coupled basis; • reusability: logic that can potentially be reused is designed as a separate service; • contract: services adhere to a communicat ions contract that defines the information exchange and any additional service description information, specified by one or more service description documents; • abstraction: beyond what is described in the service contract, services hide logic from the outside world; • composability: services may compose other services, so that logic can be represented at different levels of granularity thereby promoting reusability and the creation of abstraction layers; • autonomy: services have control over the logic they enc apsulate and are not dependent upon other services to execute this governance; • stateless: services should not be required to manage state information, as this can affect their ability to remain loosely -coupled; • discoverability: services are designed to be outwardly descriptive so that they can be found and assessed via available discovery mechanisms. 3.9 Provide an example of a service -oriented architecture. An example of SOA is shown in Figure 3.10(b). 3.10 What is Cloud computing? Cloud computing : A model for enabling ubiquitous, convenient, on -demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management ef fort or service provider interaction. See Section 3.5. 3.11 Discuss the five essential characteristics of cloud computing. The essential characteristics are: Database Systems: Instructor’s Guide - Part III 14 • On-demand self -service: consumers can obtain, configure and deploy cloud services themselves using cloud service catalogues, without requiring the assistance of anyone from the cloud provider. • Broad network access: it is network based, and accessible from anywhere, from any standardized platform (e.g. desktop computers, laptops, mobile devices). • Resource pooling. The cloud provider’s computing resources are pooled to serve multiple consumers, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. Examples of resources include storage, proce ssing, memory, and network bandwidth. • Rapid elasticity . Resource pooling avoids the capital expenditure required for the establishment of network and computing infrastructure. By outsourcing to a cloud, consumers can cater for the spikes in demand for the ir services by using the cloud provider’s computing capacity and the risk of outages and service interruptions are significantly reduced. Moreover, capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly base d on demand. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be called on in any quantity at any time. • Measured service. Cloud systems automatically control and optimize resource use by leveraging a meteri ng capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and charged for. See Section 3.5. 3.12 Discuss the three main s ervice models of cloud computing. • Software as a Service (SaaS): software and associated data are centrally hosted on the cloud. • Platform as a Service (PaaS) : a computing platform that allows the creation of web applications quickly and easily and without the complexity of buying and maintaining the software and infrastructure underneath it . Sometimes, PaaS is used to extend the capabilities of applications developed as SaaS. While earlier application development required hardware, an operating system, a d atabase, middleware, Web servers, and other software, with the PaaS model only the knowledge to integrate them is required. The rest is taken care of by the PaaS provider. • Infrastructure as a Service (IaaS): delivers servers, storage, network and operatin g systems – typically a platform virtualization environment – to consumers as an on - demand service, in a single bundle and billed according to usage . A popular use of IaaS is in hosting websites, where the in -house infrastructure is not burdened with this task but left free to manage the business. 3.13 Compare and contrast the four main deployment models for the cloud. The four main deployment models for the cloud are: Database Systems: Instructor’s Guide - Part III 15 • Private cloud: cloud infrastructure operated solely for a single organization, wheth er managed internally by the organization, a third party, or some combination of them, and it may be hosted internally or externally. • Community cloud: cloud infrastructure is shared for exclusive use by a specific community of organizations that have comm on concerns (e.g., security requirements, compliance, jurisdiction). It may be owned, managed, and operated by one or more of the organizations in the community, a third party, or some combination of them, and it may be hosted internally or externally. • Public cloud: cloud infrastructure is made available to the general public by a service provider. These services are free or offered on a pay -per-use model. It may be owned, managed, and operated by a business, academic, or government organization, or some combination of these. It exists on the premises of the cloud provider. • Hybrid cloud : cloud infrastructure is a composition of two or more distinct cloud infrastructures (private, community, or public) that remain unique entities, but are bound together by standardized or proprietary technology, offering the benefits of multiple deployment models. 3.14 What are the difference between Data as a service (DaaS) and Database as a service (DBaaS)? • DaaS: offers the ability to define data in the cloud and subseq uently query that data on demand. Unlike traditional database solutions, DaaS does not implement typical DBMS interfaces such as SQL (see Chapter 6). Instead, the data is accessed via a common set of APIs. DaaS enables any organization with valuable data t o create new revenue lines based on data they already own. Examples of DaaS are Urban Mapping, a geography data service, provides data for customers to embed into their own websites and applications; Xignite makes financial data available to customers; and Hoovers, a Dun & Bradstreet company, provides business data on various organizations. • DBaaS: offers full database functionality to application developers. In DBaaS, a management layer is responsible for the continuous monitoring and configuring of the database to achieve optimized scaling, high availability, multi -tenancy (that is, serving multiple client organizations), and effective resource allocation in the cloud, thereby sparing the developer from ongoing database administration tasks. See Section 3 .5.2. 3.15 Discuss the different architectural models for Database -as-a-service. • Separate servers • Shared Server, Separate Database Server Process • Shared Database Server, Separate Databases • Shared Database, Separate Schema • Shared Database, Shared Schema See Section 3.5.2. Database Systems: Instructor’s Guide - Part III 16 3.16 Describe the main components in a DBMS. The major software components in a DBMS environ ment are depicted in Figure 3.20 . The main components in a DBMS are: • Query processor. This is a major DBMS component that transforms queries into a series of low-level instructions directed to the database manager. • Database manager (DM). The DM interfaces with user -submitted application programs and queries. The DM accepts queries and examines the external and conceptual schemas to determine what conceptual records are required to satisfy the request. The DM then places a call to the file manager to perform the request. • File manager . The file manager manipulates the underlying storage files and manages the allocation of storage space on disk. It establishes and maintains the list of structures and indexes defined in the internal schema. If hashed files are used, it calls on the hashing functions to generate record addresses. However, the file manager does not directly manage the physical input and output of data. Rather, it passes the requests on to the appropriate access methods, which either read data from or write data into the system buffer (or cache ). • DML preprocessor . This module converts DML statements embedded in an application program i nto standard function calls in the host language. The DML preprocessor must interact with the query processor to generate the appropriate code. • DDL compiler . The DDL compiler converts DDL statements into a set of tables containing metadata. These tables ar e then stored in the system catalog while control information is stored in data file headers. • Catalog manager . The catalog manager manages access to and maintains the system catalog. The system catalog is accessed by most DBMS components. 3.17 Describe t he internal architecture of Oracle. Oracle is based on the client –server architecture. The Oracle server consists of the database (the raw data, including log and control files) and the instance (the processes and system memory on the server that provide access to the database). An instance can connect to only one database. The database consists of a logical structure , such as the database schema, and a physical structure , containing the files that make up an Oracle database. Exercises 3.18 Examine the d ocumentation sets of Microsoft SQL Server, Oracle, and IBM’s DB2 system to identify their support for the following: (a) client –server architecture (b) Web services (c) service -oriented architecture Microsoft SQL Server Microsoft SQL Server is designed t o work effectively in a number of environments: • As a two -tier or multitier client/server database system • As a desktop database system Database Systems: Instructor’s Guide - Part III 17 In a two -tier client/server system, users run an application on their local computer, known as a client, which connect s over a network to the server running SQL Server. The client application runs both business logic and the code to display output to the user, and is also known as a thick client. SQL Server 2008 enables data to be consumed from custom applications devel oped using Microsoft .NET and Visual Studio and from within service -oriented architectures (SOA) and business processes through Microsoft BizTalk Server. Web services extend the World Wide Web infrastructure to provide the means for software to connect to other software applications. Applications access Web services via ubiquitous Web protocols and data formats such as HTTP, XML, and SOAP, with no need to worry about how each Web service is implemented. Web services combine the best aspects of component -based development and the Web, and are a cornerstone of the Microsoft .NET programming model. Microsoft System Center plays a central role in Microsoft's vision to help IT organizations benefit from self -managing, dynamic systems. System Center solutions ar e tuned to simplify management of the systems and applications your company already has implemented, including Microsoft SQL Server, Microsoft Exchange Server, Microsoft Biztalk Server, Internet Information Services and the Microsoft .NET Framework. Oracl e In the Oracle database system environment, the database application and the database are separated into two parts: a front -end or client portion, and a back -end or server portion --hence the term client/server architecture. The client runs the database ap plication that accesses database information and interacts with a user through the keyboard, screen, and pointing device, such as a mouse. The server runs the Oracle software and handles the functions required for concurrent, shared data access to an Oracl e database. Although the client application and Oracle can be run on the same computer, greater efficiency can often be achieved when the client portions and server portion are run by different computers connected through a network. The following sections discuss possible variations in the Oracle client/server architecture. Most organizations implement service -oriented architecture (SOA) with the hope of gaining more business agility through reuse of shared services. As reuse begins to take hold within th e organization, however, it becomes critical to manage consumption of services or your SOA can quickly spin out of control. Oracle Web Services Manager provides a solution for governing the interactions with shared services through security and operational policy management and enforcement to ensure service reuse remains under control. Leading companies are gaining operational efficiencies and business agility through adaptable, re-usable business processes and services built on a truly flexible Service -Oriented Architecture (SOA) foundation. Oracle SOA products allow you to build, deploy, and manage SOA with integrated, best -in-class technology that provides: Database Systems: Instructor’s Guide - Part III 18 • Comprehensive and Pre -Integrated SOA Platform —Complete set of service and process infrastructure components for building, deploying, and managing SOAs • Closed -Loop Governance —Comprehensive, end -to-end lifecycle governance of services • Extreme performance and scalability —In-memory transactions, real -time event processing, and high -volume data transfer on top of a highly scalable application server • Integrated Security —Centralized policy management, enterprise -grade, end -to-end security Oracle SOA Suite, which now includes the former BEA AquaLogic Service Bus, is Oracle Fusion Middleware's strategic produc t for SOA. Oracle plans to continue to develop and support Oracle WebLogic Integration, and expects to converge this product with Oracle's strategic solutions over time. Existing deployments of this product will benefit from complementary products such as Oracle SOA Suite. DB2 Local and remote application processes can work with the same database. A remote application is one that initiates a database action from a machine that is remote from the database machine. Local applications are directly attached t o the database at the server machine. Web service providers are described by Web Services Description Language (WSDL) documents. You can use the Web services wrapper to access Web service providers. A Web services client application can obtain access to a DB2® Version 9 database with a Web services description language (WSDL) interface. You can create a WSDL interface to DB2® Version 9 data by using the Web services Object Runtime Framework (WORF), also known as Document Access Definition Extension (DADX) files. After you define the operations to access DB2 data with the DADX file, then you deploy the DADX file and its runtime environment (IBM® Web Service SOAP provider or Apache Axis version 1.2) to a supported Java ™ Web application server environment (Apa che Jakarta Tomcat or IBM® WebSphere® Application Server). After you have the DB2 Web service tested and deployed, any Web services client can start using the DB2 Web service. Web services consumer - the user -defined functions When DB2 Version 9 becomes the consumer, Web services can take advantage of the optimization that is built within the database. By using SQL statements, you can consume and integrate Web services data. By using SQL to access Web services data, you can reduce some application program ming efforts because the data can be manipulated within the context of an SQL statement before that data is returned to the client application. You can convert an existing WSDL interface into a DB2 table or scalar function by using tools that are provided in WebSphere® Studio version 5 and later. During the execution of an SQL statement, you establish a connection with the Web service provider, and then you receive a response document as a relational table or a scalar value. Database Systems: Instructor’s Guide - Part III 19 Web service providers are descr ibed by Web Services Description Language (WSDL) documents. You can use the Web services wrapper to access Web service providers. Figure 1 shows the architecture of Web services. 1. A Web service provider implements a service and publishes the WSDL informat ion to a service broker, such as UDDI. 2. The service consumer can then use the service broker to find a Web service provider. 3. When the service consumer finds a Web service provider, the service consumer binds to the service provider so that the consumer can use the Web service. 4. The consumer invokes the service by exchanging SOAP (simple object access protocol) messages between the requester and provider. Figure 1. Web services: a service -oriented architecture The SOAP specification defines the layout of an XML -based message. A SOAP message is contained in a SOAP envelope. The envelope consists of an optional SOAP header and a mandatory SOAP body. The SOAP header can contain information about the message, such as encryption information or authentication i nformation. The SOAP body contains the message. The SOAP specification also defines a default encoding for programming language bindings, which is called the SOAP encoding. 3.19 Search the Web for a number of Web services other than the ones discussed i n Section 3.2. What do these services have in common? Identify whether the services access a database. The Google Maps API provides Web services to make use of the Google Maps application. The following Web site contains a number of examples: http://maps.forum.nu/ The following site contains information on using a database with Google maps: http://groups.google.com/group/Goog le-Maps -API/web/using -databases -with-gmaps -apps Amazon provides a number of Web services discussed on the following Web site: http://aws.amazon.com/ SOLUTIONS TO REVIEW QUESTIONS AND EXERCISES FOR PART 2 – THE RELATIONAL MODEL AND LANGUAGES (CHAPTERS 4 – 9) Databas e Systems: Instructor’s Guide - Part III 2 Solutions to Review Questions and Exercises Chapter 4 The Relational Mo del ................................ ................................ ................................ ...................... 3 Chapter 5 Relational Algebra and Relational Calculus ................................ ................................ .................... 6 Chapter 6 SQL: Data Manipulation ................................ ................................ ................................ ............... 22 Chapter 7 SQL: Data Definition ................................ ................................ ................................ ..................... 32 Chapter 8 Advanced SQL ................................ ................................ ................................ .............................. 42 Chapter 9 Object -Relational DB MSs ................................ ................................ ................................ ............. 52 Databas e Systems: Instructor’s Guide - Part III 3 Chapter 4 The Relational Model Review Questions 4.1 Discuss each of the following concepts in the context of the relational data model: (a) Relation A table with columns and rows. (b) Attribute A named col umn of a relation. (c) Domain The set of allowable values for one or more attributes. (d) Tuple A row of a relation. (e) Intension The structure of a relation together with a specification of the domains and any other restrictions on possible values . Extension An instance of the tuples of a relation. (f) Degree The number of attributes in a relation. Cardinality The number of tuples in a relation. Each term defined in Section 4.2.1. 4.2 Describe the relationship between mathematical relatio ns and relations in the relational data model ? Let D1, D2, . . . , Dn be n sets. Their Cartesian product is defined as: D1  D2  . . .  Dn = {(d1, d2, . . . , dn) | d1  D1, d2  D2, . . . , dn  Dn} Any set of n-tuples from this Cartesian product is a relation on the n sets. Now let A1, A2, . . ., An be attributes with domains D1, D2, . . . , Dn. Then the set { A1:D1, A2:D2, . . . , An:Dn} is a relation schema. A relation R defined by a relation schema S is a set of mappings from the attribute names t o their corresponding domains. Thus, relation R is a set of n-tuples: (A1:d1, A2:d2, . . . , An:dn) such that d1  D1, d2  D2, . . . , dn  Dn Each element in the n-tuple consists of an attribute and a value for that attribute. Discussed fully in Sections 4.2.2 and 4.2.3. 4.3 Describe the differences between a relation and a relation schema. What is a relational database schema? A relation schema is a named relation defined by a set of attribute and domain name pairs. A relational database schema is a set of relation schemas, each with a distinct name. Discussed in Section 4.2.3. 4.4 Discuss the properties of a relation. A relation has the following properties: • has a name that is distinct from all other relation names in the relational schema; • each cell contains exactly one atomic (single) value; Databas e Systems: Instructor’s Guide - Part III 4 • each attribute has a distinct name; • the values of an attribute are all from the same domain; • each tuple is distinct; there are no duplicate tuples; • the order of attributes has no significance; • the order of tuples has no significance, theoretically. (However, in practice, the order may affect the efficiency of accessin g tuples.) Discussed fully in Section 4.2.4. 4.5 Discuss the differences between the candidate keys and the primary key of a relation. Explain what is meant by a foreign key. How do foreign keys of relations relate to candidate keys? Give examples to il lustrate your answer. The primary key is the candidate key that is selected to identify tuples uniquely within a relation. A foreign key is an attribute or set of attributes within one relation that matches the candidate key of some (possibly the same) r elation. Discussed in Section 4.2.5. 4.6 Define the two principal integrity rules for the relational model. Discuss why it is desirable to enforce these rules. Two rules are Entity Integrity (Section 4.3.2) and Referential Integrity (Section 4.3.3). 4.7 What is a view? Discuss the difference between a view and a base relation. View is the dynamic result of one or more relational operations operating on the base relations to produce another relation. Base relation exists as a set of data in the databa se. A view does not contain any data, rather a view is defined as a query on one or more base relations and a query on the view is translated into a query on the associated base relations. See Section 4.4. Exercises The following tables form part of a da tabase held in a relational DBMS: - Hotel (hotelNo , hotelName, city) Room (roomNo , hotelNo , type, price) Booking (hotelNo , guestNo , dateFrom , dateTo, roomNo) Guest (guestNo , guestName, guestAddress) where Hotel contains hotel details and hotelNo i s the primary key; Room contains room details for each hotel and (roomNo, hotelNo) forms the primary key; Booking contains details of the bookings and (hotelNo, guestNo, dateFrom) forms the primary key; and Guest contains guest details and guestNo is the primary key. Databas e Systems: Instructor’s Guide - Part III 5 4.8 Identify the foreign keys in this schema. Explain how the entity and referential integrity rules apply to these relations. For each relation, the primary key must not contain any nulls. Room is related to Hotel through the attribute hotelNo. Therefore, the hotelNo in Room should either be null or contain the number of an existing hotel in the Hotel relation. In this case study, it would probably be unacceptable to have a hotelNo in Room with a null value. Booking is r elated to Hotel through the attribute hotelNo. Therefore, the hotelNo in Booking should either be null or contain the number of an existing hotel in the Hotel relation. However, because hotelNo is also part of the primary key, a null value for this attribu te would be unacceptable. Similarly for guestNo. Booking is also related to Room through the attribute roomNo. 4.9 Produce some sample tables for these relations that observe the relational integrity rules. Suggest some general constraints that would be a ppropriate for this schema. Student should provide some sample tables, observing entity and referential integrity. In particular, ensure the uniqueness for the composite primary keys of the Room and Booking tables. Some general constraints may be: • There can be no two bookings for the same room in the same hotel on the same day. • For the Booking relation, dateFrom must be before dateTo. • Room price must be greater than 0 and less than £200. 4.10 Analyze the RDBMSs that you are currently using. Determine the support the system provides for primary keys, alternate keys, foreign keys, relational integrity , and views. This is a small student project, the result of which is dependent on the system analyzed. 4.11 Implement the above schema in one of the RDB MSs you currently use. Implement, where possible, the primary, alternate, and foreign keys, and appropriate relational integrity constraints. This is a small student project, the result of which is dependent on the RDBMS used. Ensure that keys have been implemented, and that relationships have been implemented if the RDBMS supports this. Databas e Systems: Instructor’s Guide - Part III 6 Chapter 5 Relational Algebra and Relational Calculus Review Questions 5.1 What is the difference between a procedural and non -procedural language? How would you classify the relational algebra and relational calculus? Procedural language : a language that allows user to tell the system what data is needed and exactly how to retrieve the data. Non-procedural language : a language that allows user to state what data is needed rather than how it is to be retrieved. Informally, we may describe the relational algebra as a (high -level) procedural language: it can be used to tell the DBMS how to build a new relation from one or more relations in the database. Again, inform ally, we may describe the relational calculus as a non -procedural language: it can be used to formulate the definition of a relation in terms of one or more database relations. 5.2 Explain the following terms: • relationally complete; A language that can b e used to produce any relation that can be derived using the relational calculus is said to be relationally complete . • closure of relational operations. The relational algebra is a theoretical language with operations that work on one or more relations to define another relation without changing the original relation(s). Thus, both the operands and the results are relations, and so the output from one operation can become the input to another operation. This allows expressions to be nested in the relationa l algebra, just as we can nest arithmetic operations. This property is called closure : relations are closed under the algebra, just as numbers are closed under arithmetic operations. 5.3 Define the five basic relational algebra operations. Define the Join , Intersection, and Division operations in terms of these five basic operations. Five basic operations are: • Selection and Projection (Unary) • Cartesian Product, Union, and Set Difference (Binary). There is also the Join, Intersection, and Division op erations: • Can rewrite -Join in terms of the basic selection and Cartesian product operations: Databas e Systems: Instructor’s Guide - Part III 7 R 3 F S = F (R  S) • Can express the intersection operation in terms of the set difference operation: R  S = R - (R - S) • Can express the division operati on in terms of the basic operations: T1 = C(R) T2 = C( (S x T 1) - R) T = T 1 - T2 5.4 Discuss the differences between the five Join operations: Theta join, Equijoin, Natural join, Outer join, and Semijoin. Give examples to illustrate your answer. Theta join R F S Produces a relation that contains tuples satisfying the predicate F from the Cartesian product of R and S. Equijoin R F S Produces a relation that contains tuples satisfying the predicate F (which only conta ins equality comparisons) from the Cartesian product of R and S. Natural join R S An Equijoin of the two relations R and S over all common attributes x. One occurrence of each common attribute is eliminated. (Left) Outer join R S A join in which tuples from R that do not have matching values in the common attributes of S are also included in the result relation. Semijoin R F S Produces a relation that contains the tuples of R that participate in the join of R with S. 5.5 Compare and contrast the tuple relational calculus with domain relational calculus. In particular, discuss the distinction between tuple and domain variables. In the tuple relational calculus, we use variables that range over tuples in a rel ation. In the domain relational calculus, we also use variables but in this case the variables take their values from domains of attributes rather than tuples of relations. 5.6 Define the structure of a (well -formed) formula in both the tuple relational c alculus and domain relational calculus. Tuple relational calculus A (well -formed) formula is made out of one or more atoms , where an atom has one of the following forms: • R(Si), where Si is a tuple variable and R is a relation. • Si.a1  Sj.a2, where Si and Sj are tuple variables, a1 is an attribute of the relation over which Si ranges, a2 is an attribute of the relation over which Sj ranges, and  is one of the comparison operators ( ,  , ,  , =, ); the attributes a1 and a2 must have domains whose memb ers can be compared by  Databas e Systems: Instructor’s Guide - Part III 8 • Si.a1  c, where Si is a tuple variable, a1 is an attribute of the relation over which Si ranges, c is a constant from the domain of attribute a1, and  is one of the comparison operators  We recursively build up formulae from at oms using the following rules: • an atom is a formula; • if F1 and F2 are formulae, so are their conjunction F1  F2, their disjunction F1  F2, and the negation F1; • if F is a formula with free variable X, then ( X)(F) and ( X)(F) are also formulae. Domain relational calculus A (well -formed) formula is made out of one or more atoms , where an atom has one of the following forms: • R(d1, d2,…, dn), where R is a relation of degree n and each di is a domain variable. • di  dj, where di and dj are domain variables and  is one of the comparison operators ( ,  , ,  , =, ); the domains di and dj must have members that can be compared by  • di  c, where di is a domain variable, c is a constant from the domain of di, and  is one of the comparison operators  5.7 Explain how a relational calculus expression can be unsafe? Illustrate your answer with an example. Discuss how to ensure that a relational calculus expression is safe. See end of Section 5.2.1. Exercises For the following exercises, use the Hotel sche ma defined at the start of the Exercises at the end of Chapter 4. 5.8 Describe the relations that would be produced by the following relational algebra operations: a) hotelNo (price  50 (Room ) ) This will produce a relation with a single attribute (hotelNo) giving the number of those hotels with a room price greater than £50. b) Hotel .hotelNo = Room .hotelNo (Hotel  Room ) This will produce a join of the Hotel and Room relatio ns containing all the attributes of both Hotel and Room (there will be two copies of the hotelNo attribute). Essentially this will produce a relation containing all rooms at all hotels.