Database 3&4

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 subsequently query that data ondemand. 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 to 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.

Discuss the five essential characteristics of cloud computing.

*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, processing, 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 their 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 based 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 metering 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.

Compare and contrast the four main deployment models for the cloud.

*Private cloud:* cloud infrastructure operated solely for a single organization, whether 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 common 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.

Describe the main components in a DBMS.

*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 into 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 are 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.

What are the 3 main service 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. *Infrastructure as a Service (IaaS):* delivers servers, storage, network and operating 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. acronym: SIP

SOA principles provide a unique design approach for building Web services for SOA, including:

-*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 communications 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 encapsulate 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.

What are advantages to the client-server architecture approach?

-Better performance -Likely reduction in hardware costs -Reduction in communication costs -Better consistency

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

What is a Transaction Processing (TP) Monitor?

A TP Monitor forms the middle tier of a three-tier architecture. / monitors the transfer of data between multiple local and remote terminals to ensure that the transaction processes completely or, if an error occurs, to take appropriate actions.

What is service-oriented architecture (SOA)?

A business-centric software architecture for building applications that implement business processes as sets of services published at a granularity relevant to the service consumer.

What is middleware?

A computer software that connects software components or applications.

What is an attribute?

A named column of a relation.

What is client-server architecture?

A network architecture in which each computer or process on the network is either a client or a server. The *client* process requires some resource, and the *server* provides the resource. Neither need reside on the same machine.

What does null mean?

A null represents a value for an attribute that is unknown at the present time or is not applicable for this tuple.

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; 2 -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 accessing tuples.)

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.

What is a tuple?

A row of a relation.

What is a web service?

A software system designed to support interoperable machine-to-machine interaction over a network. ---- Web services allow applications to integrate with other applications across 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.

What is a relation?

A table with columns and rows.

What is a superkey?

An attribute, or set of attributes, that identifies tuples of a relation uniquely.

What is a foreign key?

An attribute, or set of attributes, within one relation that is the candidate key of another relation.

What is extension?

An instance of the tuples of a relation.

Compare and contrast 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?

Architecture maps quite naturally to the Web with a Web browser acting as 'thin' client and Web server acting as an application server (with database server as third layer).

What is a 3-tier model?

Consists of a *user interface* layer (the *client*), a business logic and data processing layer (the *application*), and a DBMS (the *database server*) distributed over different machines. >can be expanded to "n" tiers, which provide more *flexibility* and *scalability*

What are the 2 basic categories of cloud-based databases?

Data as a Service (*DaaS*) and Database as a Service (*DBaaS*)

What is the difference between entity integrity and referential integrity?

Entity Integrity is the mechanism the system provides to maintain primary keys. The primary key serves as a unique identifier for rows in the table. Entity Integrity ensures two properties for primary keys: -The primary key for a row is unique; it does not match the primary key of any other row in the table. -The primary key is not null, no component of the primary key may be set to null. The uniqueness property ensures that the primary key of each row uniquely identifies it; there are no duplicates. The second property ensures that the primary key has meaning, has a value; no component of the key is missing. ---x--- Referential Integrity is the mechanism the system provides to maintain foreign keys. The definition of a foreign key must specify the table whose primary key is being referenced. Referential Integrity ensures only one property for foreign keys: A valid foreign key value must always reference an existing primary key or contain a null A foreign key may contain a null; it does not need to reference an existing primary key (actually, it can't reference any primary key since primary keys cannot contain nulls). In FirstSQL, foreign keys may be optionally defined as not allowing nulls. To accomplish this with other DBMSs, each component of the foreign key must be separately defined as not allowing nulls.

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 (Simple 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 interrogated by SOAP messages and to provide access to WSDL documents describing the protocol bindings and message formats required to interact with the Web services listed in its directory.

What are types of middleware?

Middleware types include *RPC* (synchronous and asynchronous), *publish/subscribe*, message-oriented middleware (*MOM*), object-request brokers (*ORB*), and *database middleware*.

What is a candidate key?

Minimum set of attributes used to uniquely identify records of the table

Describe the 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.

What are advantages of the TP monitor?

The advantages include transaction routing, distributed transactions, load balancing, funneling, and increased reliability.

What is a primary key?

The candidate key chosen for use in identification of tuples (usually in the form of an ID number) >a relation must always have a primary key

When would you need middleware?

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 incorporate frequent modifications led to the development of middleware, which hides the underlying complexity of distributed systems.

What is a degree?

The number of attributes in a relation. A unary relation has one attribute, a binary relation has two, a ternary relation has three, and an n -ary relation has n attributes.

What is Cardinality?

The number of tuples in a relation.

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 illustrate 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) relation.

What is a domain?

The set of allowable values for one or more attributes

What is intension?

The structure of a relation together with a specification of the domains and any other restrictions on possible values.

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).

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 database. 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.

What is cloud computing?

the practice of using a network of remote servers hosted on the Internet to store, manage, and process data, rather than a local server or a personal computer.