OBJECT ORIENTED DBMSbyDr. Abdus Salam

INTRODUCTION TO OODBMSLecture No. 1

Outline• Why OO Databases?• Current state of relational and Object-Relational

Databases• Features of Objected Oriented Databases• Some Leading OODBMSs

• Commercial• Academic

• Research Issues in OODBMSs

References• T. Connoly & C. Begg, Database Systems, 4th Ed

• Chapter 25, 26, 27, 28• Jeffrey A. Hoffer, V. Ramesh, Heikki Topi,

Modern Database Management Systems, 10th Ed.• Chapter 13, 14

Course of the Course• The need of OO databases• Basics of Databases as a revision

• Relational Databases• Object oriented concepts

• Data Models (Logical Model)• Relational• Hierarchical• Object Oriented (Many different models)• Object-Relational• Graph Databases

• Object-Oriented Database Management Systems• Features of OODBMSs• Different OODBMSs• Research Issues in OO DB

Why OODBMSs• Connoly Chapter 25• Two Reasons

• Requirements of Advanced DB Applications• Limitations of Relational Data Model

Why OODBMSs• Requirements of Advanced DB Applications

• computer-aided design (CAD);• computer-aided manufacturing (CAM);• computer-aided software engineering (CASE);• network management systems;• office information systems (OIS) and multimedia systems;• digital publishing;• geographic information systems (GIS);• interactive and dynamic Web sites.

Computer-aided design (CAD)• A CAD database stores data relating to mechanical and electrical

design covering, for example, buildings, aircraft, and integrated circuit chips. Designs of this type have some common characteristics:

• Design data is characterized by a large number of types, each with a small number of instances. Designs may be very large, perhaps consisting of millions of parts, often with many interdependent subsystem designs.

• Updates: One change is likely to affect a large number of design objects.

• Often, many design alternatives are being considered for each component, and the correct version for each part must be maintained. This involves some form of version control and configuration management.

• There may be hundreds of staff involved with the design, and they may work in parallel on multiple versions of a large design. Even so, the end-product must be consistent and coordinated. This is sometimes referred to as cooperative engineering.

Computer-aided manufacturing (CAM)

• A CAM database stores similar data to a CAD system, in addition to data relating to discrete production (such as cars on an assembly line) and continuous production (such as chemical synthesis).

Computer-aided software engineering (CASE)

• A CASE database stores data relating to the stages of the software development lifecycle:planning, requirements collection and analysis, design, implementation, testing, maintenance, and documentation.

Office information systems (OIS) and multimedia systems• An OIS database stores data relating to the computer

control of information in a business, including electronic mail, documents, invoices, and so on.

• To provide better support for this area, we need to handle a wider range of data types other than names, addresses, dates, and money.

• Modern systems now handle free-form text, photographs, diagrams, and audio and video sequences.

Digital publishing• The publishing industry is likely to undergo profound

changes in business practices over the next decade. • It is becoming possible to store books, journals, papers,

and articles electronically and deliver them over high-speed networks to consumers.

Geographic information systems (GIS)

• A GIS database stores various types of spatial and temporal information, such as that used in land management and underwater exploration.

• Much of the data in these systems is derived from survey and satellite photographs, and tends to be very large.

• Searches may involve identifying features based, for example, on shape, color, or texture, using advanced pattern-recognition techniques.

Interactive and dynamic Web sites• Consider a Web site that has an online catalog for selling clothes. The

Web site maintains a set of preferences for previous visitors to the site and allows a visitor to:

• browse through thumbnail images of the items in the catalog and select one to obtain a full-size image with supporting details;

• search for items that match a user-defined set of criteria;• obtain a 3D rendering of any item of clothing based on a customized

specification (for example, color, size, fabric)• modify the rendering to account for movement, illumination, backdrop,

occasion, and so on;• select accessories to go with the outfit, from items presented in a sidebar;• select a voiceover commentary giving additional details of the item;• view a running total of the bill, with appropriate discounts;• conclude the purchase through a secure online transaction.

WEAKNESSES OF RDBMSS

Why OODBMSs• Connoly Chapter 25• Two Reasons

• Requirements of Advanced DB Applications• Limitations of Relational Data Model

History of Data Models• File based Systems

• Program and Data Dependence• No Data Sharing

• Mid 60s IMS Developed • Arranges data in hierarchical form, in a tree like structure

• Same time Network Data Model was proposed• IDMS was the NDM based DBMS

• CODASYL got involved and DBTG was established

Network Data Model• In NDM, the database consists of a collection of set-type

occurrences• Each set-type occurrence has one occurrence of OWNER

RECORD, with zero or more occurrences of MEMBER RECORDS.

• To define a network database one needs to define:• The database record types which consist of data items.• The set-types

• Uses network or plex structure as its basic data structure• Node corresponds to records types and link to the

pointers.

Problems in Hierarchical and NDM• Very complex structure from the application programmer’s

point of view• Difficult to design and use properly, because of the

navigational nature of the data structure• Difficult to make changes in database• No structural independence• No theoretical foundation

Relational Data Model• Proposed by E. F. Codd in 1970• Major Strength

• Mathematical foundation• Higher degree of data independence• Expended set-oriented manipulation language (Relational Algebra)

Relational Data Model• Components of RDM:

• Structure (Relation/Table)• Manipulation Language (SQL)• Integrity Constraints

• Referential Integrity Constraint

• First two components have direct support from relational mathematics

Six Basic Properties of Relational DB Tables or Relations• Each cell of table contains atomic value• Each column has a distinct name; the name of the

attribute it represents• The values of the attributes come from the same domain• The order of the columns is immaterial• The order of rows is immaterial• Each row/tuple/record is distinct, no two rows can be the

same

Weaknesses of RDM• Poor representation of ‘real world’ entities• Semantic overloading; Semantically weak; just one structure• Poor support for integrity and enterprise constraints• Homogeneous data structure• Limited operations• Difficulty handling recursive queries• Impedance mismatch• Other problems with RDBMSs associated with concurrency,

schema changes, and poor navigational access• Table cell can store only atomic values• Normalized design recommended• ER Data Model (1976) to cater conceptual model