Future Trends: Theory and Practice. Object-oriented models. Extended relational systems ... a current situation or fashion. not of abiding interest. of ... – PowerPoint PPT presentation
- associated with formal foundations for computing
- based on mathematics (can there be any other kind of theory)
- used to justify and to inform practical principles
4 Common perceptions about theory of CS
Computer Science means accounting for computing practice using mathematical theory
Mathematical theory is the essential foundation practical computing is its application
The mathematical foundations of computer science are the bedrock of the subject - they frame computing in an abstract manner independent of technologies and how these abstractions are realised in practice is a relatively ephemeral concern
5
Ephemeral conveys a number of ideas
temporary
reflecting a current situation or fashion
not of abiding interest
of subordinate significance
6 In support of this view of theory
From a mathematical perspective
have a powerful abstract theory of computation all programming platforms are Turing equivalent in some fundamental sense
it is difficult to know what meaning to attach to computational activity for which there is no abstract mathematical model
computation has - and always has had - a crucial role in mathematics itself
7 In support of this view of theory
From a broader scientific perspective
It is possible to regard pure sciences such as physics as establishing an intimate association between mathematical models and our interaction with the natural world
CS might plausibly be viewed as an embryonic Science of the Artificial and we might expect abstract mathematical models to be ideally suited to framing such a discipline
8 In support of this view of theory
From a cognitive perspective
reasoning is an important constituent of human thought - logic is seen by many computer / cognitive scientists as the essential constituent of human intelligence and the computer as an appropriate metaphor for the brain
cf. the logicist perspective on artificial intelligence
9 Contrary to this view
Theory has yet to deliver programming tools and principles that meet practical computing needs comprehensively
Functional programming
Formal models of concurrency
Formal methods for software development
represent a partial solution to practical issues
10 Contrary to this view
Crucial aspects of practical computing have no satisfactory supporting formal theory
human-computer interaction
end-user programming
object-oriented modelling
object-oriented software development
mathematical models are of limited value
11 Contrary to this view
Some of the most significant aspects of computing practice are pre-theory and subjective in character
Consider the observation and experiment involved e.g.
in requirements capture
in customising interfaces for personal use
in software development based on prototyping
implicit knowledge embodied in interaction not explicit in mathematical models
12 Contrary to this view
Interaction in the world can only be viewed as accounted for by theory if we accept a reductionist stance on the nature of science consider the implications / meta-implications of a Theory of Everything in physics
Many aspects of human activity and interaction in the world arguably involve more than applications of logic interaction in the world can be viewed as conceptually prior to reasoning and not explicable in terms of logic consider e.g. Rodney Brookss robotics research on themes such as Intelligence without Reason Intelligence without Representation
13 Contrary to this view
Modern developments of computing challenge the mind-body dualism that underlies the idea of the brain as a complex computational device that can be conceptually separated from its embodiment consider e.g.
- brain-mediated communication
- meaning as situated
- context dependence in natural language
Mathematics does not account for situated meaning
14 Two possible approaches to developing CS
evolutionary accept that there is an essential duality within computing that distinguishes the hard core science of computing from the soft ephemeral pseudo-science of computing practice and focus on developing and extending classical theories with a view to giving as comprehensive an account of computing practice as is possible
revolutionary recognise that computer science as classically conceived is inadequate as a foundation for practical computing and artificial intelligence and that this inadequacy cannot be resolved without reappraising the whole issue of how mathematical models and activities in the world are connected
15 Scope of CS 319
Will use data modelling principles for databases as the arena within which to explore these broad issues concerning the role of theory in computer science
Complementary to other modules e.g. that concern
formal approaches to software development
artificial intelligence
robotics
personal views beyond scope of CS319 developed in CS405 An Introduction to Empirical Modelling
16 The principal theme of CS319
How do theory and computing practice relate with specific reference to databases
Key ideas
The counterpart of the classical theory of computation in databases is Codds relational theory.
There is an excellent correspondence between relational theory and practical database application of a certain kind.
Relational databases can be seen as a precursor for two principal kinds of computer application environments for end-user programming and computer-based models of real-world state.
17 The principal theme of CS319
How do theory and computing practice relate with specific reference to databases
Key ideas (cont.)
There are aspects to the relational theory (especially those concerned with database design) that challenge the classical view of how an abstract mathematical model represents a situation in the world.
Modern database applications oblige us to question the adequacy of relational theory and to consider the extent to which a relational framework can cope with notions such as objects interfaces and agents.
18 Content of CS319
To put the key ideas in perspective address the following topics
An extended account of relational theory and its applications in respect of the development of relational query language and database design.
The qualities of the relational model both as it was first conceived by Codd and as it has (and has not) been embodied in practical relational databases.
19 Content of CS319
A critical assessment of the relational database model from the proponents of alternative kinds of database such as object-oriented and extended relational models.
The possible limitations of the relational model where modern computing applications and technologies are concerned.
An evaluation of the various database model critiques and a personal perspective on the future of databases.
20 Aspects of a Computer Science education
Three kinds of activity involved in learning CS
learning theory
gaining practical knowledge and skills of computing
developing a critical appreciation of how theory and practice are related
Principal emphasis in CS319 is on the first and third aspects
21 Special lecture arrangements weeks 18 and 19
Dr Hugh Darwen was an IBM consultant on databases
he is our guest lecturer in weeks 18 and 19
NOTE the lectures in week 18 will be on The Relational Model and SQL thus
Monday February 21st at 2pm and 5pm in CS1.04
Thursday February 24th at 2pm and 5pm in CS1.04
the lectures in week 19 will be on
Temporal Data and the Relational Model thus
Monday February 28th at 2pm and 5pm in CS1.04
Thursday March 3rd at 2pm and 5pm in CS1.04
22 Some context for the Theory of Databases
Setting the scene
Industrial perspectives
Academic perspectives
Sources for the CS319 module
23 Setting the scene for the theory of databases - relations
M J Ridley University of Bradford (TLAD WS 2003)
DB systems or DB theory or Why dont you teach ORACLE
The modern age of databases may NB! - WMB have started with relational databases which despite their ubiquitous nature we should remember were looked an as of only academic interest at one time. What surely marks this era the early 1970s out is the sound theoretical basis of that database model and the progress that was made because of this.
But what age are we in now
24 Setting the scene for the theory of databases - objects
Object oriented DBs emerged in the 1980s in response to the feeling that relational databases were inadequate for certain classes of applications ...
Disadvantages of OODBs
Brown A.W. OODBs Applications in S/W Engineering 1991
no formal semantics
loss of relational simplicity
navigational queries
no general query language
25 Setting the scene for the theory of databases objrel
Object oriented DBs emerged in the 1980s in response to the feeling that relational databases were inadequate for certain classes of applications ... The extent to which object-oriented and relational DBs can be unified as in object-relational DBs remains controversial
Ridley cites Maier (2002) on object-relational systems
David Maier speaks out SIGMOD Record 31(4) 2002 http//www.acm.org/sigmod/record/issues/0212/
theres not a good design theory the way there was with normal form relations for relational databases
the new features at least double the number of design choices you have in every instance
26 Setting the scene for the theory of databases the Web
Ridley observes The Web has made many more people database users and heightened the awareness of databases generally it raises the issues of the semantic mismatch between the set oriented nature of SQL and most programming languages. cites
The Asilomar report on Database Research SIGMOD Record 27(4) 1998 http//www.acm.org/sigmod/reco rd/issues/9812/
Theorem The WEB changes everything.
Corollary XML is the means
and raises the question
But where then is our dominant relational paradigm left
27 Perspectives from the computing industry 1
From Whatever happened to OODBs
http//www.leavcom/db_08_00.html
In 1998 industry experts touted OODBs as a technology on the rise well suited for the emerging Internet age OODBs would soon become the primary DB technology supplanting RDBMSs which were not designed to handle multimedia data Fast forward to today and RDBs are still by far the most widely used DBs meanwhile object-relational DBMSs have added object capabilities to relational DBs they are gaining popularity and are expected to outsell even RDBs by 2003
28 Perspectives from the computing industry 2
Rick Catell (SUN Microsystems) Object-oriented DBs are doing just fine and the news of their demise is greatly exaggerated. While their market isnt as big they continue to be used in areas like CAD (computer-aided design) and telecommunications where RDBMSs are not well suited.
Michael Stonebraker (Informix) ODBMSs occupy a small niche market that has no broad appeal. The technology is in semi-rigor mortis and ORDBMSs will corner the market within five years.
quotations dating from around the year 2000
29 Perspectives from the computing industry 3
International Data Corporation Opinion
from OODB vs ORDBs Steve McClure 1997
Because of the relative size of the RDBMS vendors marketing infrastructures the ORDBMS market will surpass the size of the ODBMS market in the next five years. Nevertheless putting object-oriented extensions on RDBMSs is tantamount to adding stereo radios and global navigation systems to horse-drawn carriages. You will have interesting enhancements but the wrong base vehicle. In the end it wont be an appropriate vehicle for the information superhighway.
30 Perspectives from academia 1
M J Ridley University of Bradford (TLAD WS 2003)
DB systems or DB theory or Why dont you teach ORACLE
Practice without Theory is blind Theory without Practice is sterile (Karl Marx)
most people would agree that we need a theoretical framework in which to talk about DBs if the result is to be productive The questions that seem to me to need answering are What is that framework
31 Perspectives from academia 2
M J Ridley University of Bradford (TLAD WS 2003)
DB systems or DB theory or Why dont you teach ORACLE
most people would agree that we need a theoretical framework in which to talk about DBs if the result is to be productive The questions that seem to me to need answering are What is that framework
Is it the simple relational model How important is that framework (In practical educational terms how much of the syllabus is this) Are there competing theoretical frameworks that need considering
32 Perspectives from academia 3
M J Ridley University of Bradford (TLAD WS 2003)
DB systems or DB theory or Why dont you teach ORACLE
most people would agree that we need a theoretical framework in which to talk about DBs if the result is to be productive
But is there still a firm theoretical foundation for what we teach Does that matter Are we in danger of training students in the features of a particular system (and a convenient web interface for it) rather than educating them about DBs in the broader sense
33 Perspectives from academia 4
M J Ridley University of Bradford (TLAD WS 2003)
DB systems or DB theory or Why dont you teach ORACLE
What is the relationship of Database teaching to other aspects of the curriculum such as the study of data structures and object-orientation And are there theories of these subjects
is there are more general object theory that informs programming and software development generally. If so can relational theory be located as a subset of that mainstream or does database stand out as an exception
34 Perspectives from academia 5
M J Ridley University of Bradford (TLAD WS 2003)
DB systems or DB theory or Why dont you teach ORACLE
Ridleys own answer to these questions
we are in danger of losing sight of firm theoretical ground especially as we are under pressure to include yet more additional facilities of DBMSs more so as object systems have failed to achieve commercial success commensurate with their early promise and the pressure of the web has shifted the focus of much database work.
35 Books on Classical Relational Databases
Date C.J. A Database Primer Addison-Wesley
Date C.J. An Introduction to Database Systems Addison-Wesley 8th edition 2003
Ullman J.D. Principles of Database Systems 2nd edition Computer Science Press 1982
Ullman J.D. Principles of Database Knowledge-base Systems Vols 1 2 Computer Science Press 1988
Ullman J.D. A First Course in Database Systems 2nd ed Prentice-Hall 2002
see http//www-db.stanford.edu/ullman/ullman-bo oks.html
36 Books on more general database issues
Korth H.F. and Silberschatz Database System Concepts McGraw-Hill 2nd ed. 1991 4th ed. 2001
Brown A.W. Object-oriented Databases Applications in Software Engineering McGraw-Hill International Series in Engineering 1991
Gray P.D. Logic Algebra Databases Ellis-Horwood Series Computers and their Applications 29
Kent William Data and Reality basic assumptions in data processing reconsidered North-Holland 1987
37 Books on Relational Theory in its application
Date C.J. Relational Database Writings 1985-1989 Addison-Wesley and other collections in this series
Hugh Darwen and C.J.Date Foundations for Object/Relational Databases The Third Manifesto 1998 Harlow Addison-Wesley Longman
C.J.Date Hugh Darwen M.A.Lorentzos Temporal Data and the Relational Model Morgan-Kaufmann 2002
(summarised in Chap. 23 of Dates Intro to DBs 8th ed)
Dr Hugh Darwen was an IBM consultant on database
until his retirement in 2004 he is our guest lecturer in
weeks 18 and 19
38 Special lecture arrangements weeks 18 and 19
Dr Hugh Darwen was an IBM consultant on databases
he is our guest lecturer in weeks 18 and 19
NOTE the lectures in week 18 will be on The Relational Model and SQL thus
Monday February 21st at 2pm and 5pm in CS1.04
Thursday February 24th at 2pm and 5pm in CS1.04
the lectures in week 19 will be on
Temporal Data and the Relational Model thus
Monday February 28th at 2pm and 5pm in CS1.04
Thursday March 3rd at 2pm and 5pm in CS1.04
39 Questions regarding status of DB theory 1
Issues about the context in which DB theory applies
To what extent do theories about databases in general apply exclusively to relational databases
To what extent is DB theory specific to applications
- technology / kind of activity / nature of environment
it applies to the 1970s business context does it apply now
40 Questions regarding status of DB theory 2
Issues about the scope and nature of DB theory itself
How does DB theory relate to objectives such as
- supporting end-user programming
- representing real-world state
How does DB theory relate to other conceptual frameworks (e.g. data modelling in OO / UML / ER)
to address broader issues (e.g. typing / non-procedural vs procedural models of computation)
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