Database Architecture - Ch 2

A Schema Construct is:

A component of the schema or an object within the schema, e.g., STUDENT, COURSE.

A Data Model is

A set of concepts to describe the structure of a database, the operations for manipulating these structures, and certain constraints that the database should obey.

A Valid State is:

A state that satisfies the structure and constraints of the database.

A Schema Diagram is:

An illustrative display of (most aspects of) a database schema.

describe High Level or Non-procedural Language

Are "set"-oriented and specify what data to retrieve rather than how to retrieve it. Also called declarative languages. (For example, the SQL relational language)

What Provide appropriate interfaces through a client software module to access and utilize the various server resources?

Clients

__________ are connected to the servers via some form of a network. (LAN: local area network, wireless network, etc.)

Clients

__________ may be diskless machines or PCs or Workstations with disks with only the client software installed

Clients

The Self-Describing Data Model functions to:

Combine the description of data with the data values. Examples include XML, key-value stores and some NOSQL systems

Describe a Centralized DBMS

Combines everything into single system including- DBMS software, hardware, application programs, and user interface processing software. User can still connect through a remote terminal - however, all processing is done at centralized site.

4 categories of data models

Conceptual (high-level, semantic) Physical (low-level, internal) Implementation (representational) Implementation (representational)

3 Data Model Structure and Constraints are:

Constructs are used to define the database structure Constructs typically include elements (and their data types) as well as groups of elements (e.g. entity, record, table), and relationships among such groups Constraints specify some restrictions on valid data; these constraints must be enforced at all times

5 considerations for DBMSs

Cost Range: from free open-source systems to configurations costing millions of dollars Commercial DBMS offer additional specialized modules, e.g. time-series module, spatial data module, document module, XML module -These offer additional specialized functionality when purchased separately -Sometimes called cartridges (e.g., in Oracle) or blades Different licensing options: site license, maximum number of concurrent users (seat license), single user, etc. Type of access paths within database system General Purpose vs. Special Purpose

_____________ Applications running on clients utilize an Application Program Interface (API) to access server databases via standard interface such as: -ODBC: Open Database Connectivity standard -JDBC: for Java programming access

DBMS server

____________________ provides database query and transaction services to the clients

DBMS server

DDL stands for

Data Definition Language

DML stands for

Data Manipulation Language

Three-tier Architecture Can Enhance Security in what 4 ways?

Database server only accessible via middle tier Clients cannot directly access database server Clients contain user interfaces and Web browsers The client is typically a PC or a mobile device connected to the Web

what are the 4 Programmer interfaces for embedding DML in a programming language

Embedded Approach: e.g embedded SQL (for C, C++, etc.), SQLJ (for Java) Procedure Call Approach: e.g. JDBC for Java, ODBC (Open Databse Connectivity) for other programming languages as API's (application programming interfaces) Database Programming Language Approach: e.g. ORACLE has PL/SQL, a programming language based on SQL; language incorporates SQL and its data types as integral components Scripting Languages: PHP (client-side scripting) and Python (server-side scripting) are used to write database programs.

4 Variations of Distributed DBMSs

Homogeneous DDBMS Heterogeneous DDBMS Federated or Multidatabase System -Participating Databases are loosely coupled with high degree of autonomy. Distributed Database Systems have now come to be known as client-server based database systems because: -They do not support a totally distributed environment, but rather a set of database servers supporting a set of clients.

Three-Schema Architecture Defines DBMS schemas at three levels. Those being:

Internal schema at the internal level to describe physical storage structures and access paths (e.g indexes). -Typically uses a physical data model. Conceptual schema at the conceptual level to describe the structure and constraints for the whole database for a community of users. -Uses a conceptual or an implementation data model. External schemas at the external level to describe the various user views. -Usually uses the same data model as the conceptual schema.

5 Classification of DBMSs

Legacy: Network, Hierarchical. Currently Used: Relational, Object-oriented, Object-relational Recent Technologies: Key-value storage systems, NOSQL systems: document based, column-based, graph-based and key-value based. Native XML DBMSs. Single user (typically used with personal computers) vs. multi-user (most DBMSs). Centralized (uses a single computer with one database) vs. distributed (multiple computers, multiple DBs)

Database System Utilities perform certain functions such as

Loading data stored in files into a database. Includes data conversion tools. Backing up the database periodically on tape. Reorganizing database file structures. Performance monitoring utilities. Report generation utilities. Other functions, such as sorting, user monitoring, data compression, etc.

two types of data independence

Logical Data Physical Data

High-Level or Non-procedural Languages are employed how?

May be used in a standalone way or may be embedded in a programming language (These include the relational language SQL)

What are 5 User-Friendly DBMS Interfaces

Menu-based (Web-based), popular for browsing on the web Forms-based, designed for naïve users used to filling in entries on a form Graphics-based -Point and Click, Drag and Drop, etc. -Specifying a query on a schema diagram Natural language: requests in written English Combinations of the above: For example, both menus and forms used extensively in Web database interfaces

What are 5 (other) DBMS Interfaces

Natural language: free text as a query Speech : Input query and Output response Web Browser with keyword search Parametric interfaces, e.g., bank tellers using function keys. Interfaces for the DBA: -Creating user accounts, granting authorizations -Setting system parameters -Changing schemas or access paths

How does Three-Schema Architecture relate to commercial DBMS products

Not explicitly used in commercial DBMS products, but has been useful in explaining database system organization

Client and server must install appropriate client module and server module software for ________ or ________

ODBC JDBC

Give 3 examples of the DBMS tool "Application Development Environments and CASE (computer-aided software engineering)"

PowerBuilder (Sybase) JBuilder (Borland) JDeveloper 10G (Oracle)

What are 5 Specialized Servers with Specialized functions

Print server File server DBMS server Web server Email server (Clients can access the specialized servers as needed)

Three-Schema Architecture is Proposed to support DBMS characteristics of

Program-data independence. Support of multiple views of the data.

In Three-Schema Architecture, Mappings among schema levels are needed to transform requests and data. How is this done?

Programs refer to an external schema, and are mapped by the DBMS to the internal schema for execution. Data extracted from the internal DBMS level is reformatted to match the user's external view (e.g. formatting the results of an SQL query for display in a Web page)

The Conceptual (high-level, semantic) data model category functions to:

Provide concepts that are close to the way many users perceive data. (Also called entity-based or object-based data models.)

The Physical (low-level, internal) data model functions to:

Provide concepts that describe details of how data is stored in the computer. These are usually specified in an ad-hoc manner through DBMS design and administration manuals

The Implementation (representational) data model functions to:

Provide concepts that fall between the above two, used by many commercial DBMS implementations (e.g. relational data models used in many commercial systems).

An Initial Database State is:

Refers to the database state when it is initially loaded into the system.

____________ servers are often called SQL servers, query servers, or transaction servers

Relational DBMS

describe Low Level or Procedural Language

Retrieve data one record-at-a-time Constructs such as looping are needed to retrieve multiple records, along with positioning pointers.

What are 4 DBMS interfaces

Stand-alone query language interfaces -Example: Entering SQL queries at the DBMS interactive SQL interface (e.g. SQL*Plus in ORACLE) Programmer interfaces for embedding DML in programming languages User-friendly interfaces -Menu-based, forms-based, graphics-based, etc. Mobile Interfaces: interfaces allowing users to perform transactions using mobile apps

Intermediate Layer called Application Server or Web Server:

Stores the web connectivity software and the business logic part of the application used to access the corresponding data from the database server Acts like a conduit for sending partially processed data between the database server and the client.

A Database State is:

The actual data stored in a database at a particular moment in time. This includes the collection of all the data in the database. Also called database instance (or occurrence or snapshot). -The term instance is also applied to individual database components, e.g. record instance, table instance, entity instance

Logical Data Independence

The capacity to change the conceptual schema without having to change the external schemas and their associated application programs.

Physical Data Independence

The capacity to change the internal schema without having to change the conceptual schema. For example, the internal schema may be changed when certain file structures are reorganized or new indexes are created to improve database performance

What is the main distinction between database STATE and database SCHEMA?

The database schema changes very infrequently. The database state changes every time the database is updated.

A Database Schema is:

The description of a database. Includes descriptions of the database structure, data types, and the constraints on the database.

Low Level or Procedural Languages are employed how?

These must be embedded in a programming language

What are Data Model Operations:

These operations are used for specifying database retrievals and updates by referring to the constructs of the data model. Operations on the data model may include basic model operations (e.g. generic insert, delete, update) and user-defined operations (e.g. compute_student_gpa, update_inventory)

describe Data Definition Language (DDL)

Used by the DBA and database designers to specify the conceptual schema of a database. In many DBMSs, the DDL is also used to define internal and external schemas (views). In some DBMSs, separate storage definition language (SDL) and view definition language (VDL) are used to define internal and external schemas. -SDL is typically realized via DBMS commands provided to the DBA and database designers

describe Data Manipulation Language (DML)

Used to specify database retrievals and updates DML commands (data sublanguage) can be embedded in a general-purpose programming language (host language), such as COBOL, C, C++, or Java. -A library of functions can also be provided to access the DBMS from a programming language Alternatively, stand-alone DML commands can be applied directly (called a query language).

Describe DBMS tool "Data dictionary / repository"

Used to store schema descriptions and other information such as design decisions, application program descriptions, user information, usage standards, etc. Active data dictionary is accessed by DBMS software and users/DBA. Passive data dictionary is accessed by users/DBA only.

Three Tier Client-Server Architecture is Common for ____________

Web applications

A client program may connect to several DBMSs, sometimes called the ____________.

data sources

In general, _____________ can be files or other non-DBMS software that manages data.

data sources

State is also called ______

extension

Schema is also called ________

intension

When a schema at a lower level is changed, only the __________ between this schema and higher-level schemas need to be changed in a DBMS that fully supports data independence. The higher-level schemas themselves are ________

mappings unchanged (Hence, the application programs need not be changed since they refer to the external schemas.)

SDL stands for?

storage definition language

VDL stands for?

view definition language