Third-Generation Database System Manifesto

The Committee for Advanced DBMS Systems

Michael Stonebraker, Lawrence A. Rowe, Bruce Lindsay, James Gray,

Michael Carey, Michael Brodie, Philip Bernstein, David Beech

ACM SIGMOD Record, Sep'1990

First generation database systems

• The network and hierarchical databases of the 1970’s

• The first systems to offer DBMS function in a unified system

• e.g. CODASYL, IMS

Second generation database systems

• relational databases of the 1980’s

• data independence and non procedural data manipulation language

• e.g. DB2, INGRES, NON-STOP SQL, ORACLE, Rdb/VMS

• Focused on business data processing

Third generation database systems

• Problems with 2nd generation DBS– inadequate for a broader class of applications (than business data

processing)– e.g. CAD, CASE, Hypertext, – storing text segments, graphics, etc is usually difficult in 2nd gen.

systems– Does not support complex data (folders)

• Most vendors are working on functional enhancements on their 2nd gen. systems

• Surprising degree of consensus on these features • 3rd gen systems includes the desired capabilities of next

generation database systems

The tenets of third generation DBMS Tenet 1

• Besides traditional data management services, third generation DBMS will provide support for richer object structures and rules

• richer object structures characterize the capabilities to store and manipulate e.g. text and spatial data

• designer should be given the capability to specify a set of rules about data elements, records and collections

The tenets of third generation DBMS Tenet 2

• Third generation DBMSs must subsume second generation DBMSs

• The major contribution of 2nd gen. DBMS:– non procedural access– data independence

• A query language is an absolute requirement• Data independence have dramatically lowered the

amount of program maintenance that must be done by applications and should not be abandoned

The tenets of third generation DBMS Tenet 3

• Third generation DBMSs must be open to other subsystems• Must have

– fourth generation language– various decision support tools– friendly access from many programming languages– interfaces to business graphics packages– the ability to run the application on a different machine than the

DBMS– ......

• Third generation DBMS must be open• Must be willing to participate in future distributed DBMS

systems

Propositions concerning object and rule management

• A third generation DBMS must have a rich type system (se list in article)

• Inheritance is a good idea• Functions including database procedures and methods,

and encapsulation are a good idea• Unique identifiers for records should be assigned by the

DBMS only if a user defined primary key is not available

• Rules (triggers, constraints) will become a major feature in future systems. They should not be associated with a specific function or collection

Propositions concerning increasing DBMS function

• Essentially all programmatic access to a database should be through a non.procedural, high-level access language

• There should be at least two ways to specify collections, one using enumeration of members and one using the query language to specify membership

• Updateable views are essential• performance indicators have almost nothing to do

with data models and must not appear in them

Propositions that results from the necessity of an open system

• Third generation DBMS must be accessible form multiple HLLs

• Persistent X for variety of Xs is a good idea. They will be supported on top of a single DBMS by compiler extensions and a (more or less) complex run time system

• For better or worse, SQL is intergalactic dataspeak• Queries and their resulting answers should be the

lowest level of communication between a client and a server

Summary

• Agree with OODB enthusiast on:– rich type system, functions, inheritance,

encapsulation

• Disagree– to narrowly focused on object management

issues– non-SQL, single language systems appealing to

a fairly narrow market

Summary cont.

• DMBS access should only occur through a query language (20 years of history is convincing)

• Physical navigation by user programs and functions should be avoided

• Automatic collections should be encouraged• Persistence should be added to a variety of programming

languages (this has little to do with the data model)• Unique identifiers should be user defined or system

defined•

Summary cont.

• A natural evolution from current RDBS to the ones with the capabilities discussed in this paper

• Many of the features are already supported by ”aggressive” RDBS vendors– inheritance, additional type constructors, persistent programming

languages must be supported

• Current ODBS are not faithful to any of the tenets and some of the propositions – query languages, rule system, SQL client/server support, views,

persistent programming languages must be supported– must undo hard coded requirements for UID and discourage navigation– must build 4GL, support distributed databases, tune systems to perform

efficient data management

Research and development challenges

• The design of persistent programming languages for existing HLL

• The inclusion of pleasing query language constructs

• Logical and physical database design will get more difficult with richer type systems and rules

• Optimisation of the execution of rules• Tools to allow users to visualize and debug rule

oriented applications