Design of Expert Systems

7/21/2019 Design of Expert Systems

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Unit 6:

Design of Expert

Systems

CSEP508

(K2213)


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Figure 6.1 Project Management Tasks


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Selecting the Appropriate

Problem

We need to answer the questions, Why are we

buiding this expert system!"#

$%ntee&tua 'roperty (greement must be &onsidered

$)eary identify the probem

$)eary identify the expert

$)eary identify the users

We need to *now the payoff $ money, effi&ien&y, et


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Problem

What toos wi be a+aiabe to buid the expert system!

$ 3rdlaw o !isdom" if you-re ost, as* someone#. )he&* the Web

for appi&ations in existen&e

$ #nd law o !isdom" if you-re going to as* someone for hep, it-sgood idea to *now the anguage#. /now the anguage

ne&essary to &reate a semanti& net of reationships on whi&h the

system wi be based


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Problem

0ow mu&h wi the expert system &ost!

$ 1st law o !isdom" %f you-+e bought a &ar and are not worried

about the &ost of gas, it-s is a good idea to own your own oi we#

$ $ero law o !isdom" %t-s better to use someone ese-s &ar and gas#

$ ( fun&tion of peope, resour&es, time, et

$ 0ow a+aiabe is the *nowedge!


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Stages in the %e&elopment

0ow wi the system be de+eoped!

$ 1his wi depend on the resour&es pro+ided

Stages:

2# 3easibiity Study $ see if the pro4e&t is feasibe

5# apid 'rototype $ demonstrate ideas 7 impress

8# efined System $ +erifi&ation by *nowedge engineers

9# 3ied 1estabe $ system tested by see&ted users

# )ommer&ia quaity system $ +aidation 7 testing

6# ;aintenan&e and e+oution $ repair bugs, enhan&e &apabiities


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'ther (onsiderations

0ow wi the system be dei+ered!

$Shoud be &onsidered in eariest stages of de+eopment

$%ntegration with existing programs

0ow wi the system be maintained and e+o+e!$)1 law o !isdom" %f you don-t ha+e a spe&ifi& destination, go

e+erywhere be&ause you ne+er *now what you are missing#.

$'erforman&e is dependent on *nowedge 7 expertise

$'erforman&e must be maintained$


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Figure 6.# *eneral Stages in the

%e&elopment o an +,pert S-stem


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+rrors in %e&elopment Stages

Expert-s *nowedge may be erroneous,

propagating errors throughout the entire

de+eopment pro&ess#

> )# law o !isdom" %f you are going to set out on

a 4ourney, %t-s good if you o+e to 4ourney#.

$3orma pro&edures may be ne&essary to &ertify expert

$1e&hnique panes &an s&rutini?e expert-s *nowedge

$3o&us groups &an aso be used attempting to find out

what wi reay se#.


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+rrors in the %e&elopment Stages

/nowedge may not be propery &ommuni&ated to *nowedge

engineer, or *nowedge may be misinterpreted#

/nowedge base may be &orrupted by entering in&orre&t form

of a rue or fa&t#

%nferen&e engine errors may resut from errors in pattern

mat&hing, &onfi&t resoution, and exe&ution of a&tions#

%nferen&e &hain errors may be &aused by erroneous *nowedge,

semanti& errors, inferen&e engine bugs, in&orre&t spe&ifi&ations

of rue priorities, and strange intera&tion among rues#

@imits of ignoran&e $ a probem &ommon to a pre+ious stages


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Figure 6.3 Major +rrors in +,pert

S-stems and Some (auses


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Sotware +ngineering

and +,pert S-stems

Expert systems are produ&ts i*e any other

software produ&t and require good standards for

de+eopment# Expert systems may ha+e serious responsibiities

$ ife and death#

0igh standards are a ne&essity and &an bemeasured by mean time between faiures"#


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Figure 6. Sotware +ngineering

Methodolog-


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+,pert S-stem /ie (-cle

Aegins with the initia &on&ept of the software andends with its retirement from use#

)3 law o !isdom" %f you don-t o+e to 4ourney,then o+e what you ha+e got.

Expert systems require more maintenan&e be&ausethey are based on *nowedge that is:

$0euristi&

$Experientia

( number of ife &y&e modes ha+e been de+eoped#


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!aterall Model

Ea&h stage ends with a +erifi&ation and

+aidation a&ti+ity to minimi?e any probems in

that stage# (rrows go ba&* and forth ony one stage at a

time#

%t is assumed that a information ne&essary fora stage is *nown#


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Figure 6.0 !aterall Model o the

Sotware /ie (-cle


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(ode)and)Fi, Model

Some &ode is written and then fixed when it does

not wor* &orre&ty#

Usuay the method of &hoi&e for newprogramming students in &on+entiona and expert

systems

1his e+entuay ed to the do>it>twi&e &on&eptwhere a prototype then a fina system was buit#


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ncremental Model

1his is a refinement of the waterfa and top>

down>approa&h#

1he idea is to de+eop software in in&rements offun&tiona &apabiity#

$;a4or in&rement $ assistant&oeagueexpert

$;inor in&rement $ expertise within ea&h e+e$;i&roin&rement $ add7refining indi+idua rues


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Spiral Model

Ea&h &ir&uit of the spira adds some fun&tiona

&apabiity to the system#


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%etailed /ie (-cle Model

/inear Model

2# 'anning Stage

1he purpose of this stage is to produ&e a forma wor* pan for

the expert system de+eopment $ do&uments to guide and

e+auate the de+eopment#


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/inear Model

5# /nowedge Definition

1he ob4e&ti+e of this stage is to define the

*nowedge requirements of the expert system,

whi&h &onsists of two main tas*s:

/nowedge sour&e identifi&ation and see&tion

/nowedge a&quisition, anaysis, and extra&tion


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Table 6.3 2nowledge Source

dentiication


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Table 6. 2nowledge Ac4uisition5

Anal-sis5 and +,traction Tasks


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/inear Model

8# /nowedgeDesign

1he ob4e&ti+e is to produ&e the detaied design

for an expert system and in+o+es:

/nowedge definition

Detaied design


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Table 6.0 2nowledge %einition

Tasks


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Table 6.6 %etailed %esign o

2nowledge Tasks


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/inear Model

9# )ode and )he&*out

1his begins the a&tua &ode impementation


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/inear Model

# /nowedge Berifi&ation

1he ob4e&ti+e here is to determine the

&orre&tness, &ompeteness, and &onsisten&y ofthe system#

3orma tests

1est (naysis


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1abe 6#C 3orma 1est 1as*s of /nowedge Berifi&ation Stage

1est (naysis 1as*s


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/inear Model

6# System E+auation

1his stage is for summari?ing what has been

earned with re&ommendations for impro+ementsand &orre&tions#


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Figure 6. /inear Model o +,pert

S-stem %e&elopment /ie (-cle


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Summar-

%n this &hapter, we ha+e dis&ussed a software

engineering approa&h to the &onstru&tion of an

expert system# 'rin&ipes about good inter+iewing te&hniques

were mentioned#


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Summar-

3a&tors to be &onsidered in the design of expert

systems in&ude probem see&tion, &ost, and

payoff# Aoth manageria and te&hni&a aspe&ts must be

&onsidered#

Ay &onsistenty foowing the outined ife&y&e" it shoud be possibe to &onstru&t quaity

software#


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Design of Expert Systems

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