distributed object-based systemscrystal.uta.edu/~elmasri/os2/slides/tanenbaum/ch9.pdfmessaging no...

Dis

tribu

ted

Obj

ect-B

ased

Sy

stem

s

Cha

pter

9

Ove

rvie

w o

f CO

RB

A

The

glob

al a

rchi

tect

ure

of C

OR

BA

.

Obj

ect M

odel

The

gene

ral o

rgan

izat

ion

of a

CO

RB

A sy

stem

.

Cor

ba S

ervi

ces

Ove

rvie

w o

f CO

RB

A se

rvic

es.

Prov

ides

the

curre

nt ti

me

with

in s

peci

fied

erro

r mar

gins

Tim

e

Mec

hani

sms

for s

ecur

e ch

anne

ls, a

utho

rizat

ion,

and

aud

iting

Secu

rity

Faci

litie

s fo

r exp

ress

ing

rela

tions

hips

bet

wee

n ob

ject

sR

elat

ions

hip

Faci

litie

s fo

r per

sist

ently

sto

ring

obje

cts

Pers

iste

nce

Faci

litie

s to

pub

lish

and

find

the

serv

ices

on

obje

ct h

as to

offe

rTr

adin

g

Faci

litie

s fo

r ass

ocia

ting

(attr

ibut

e, v

alue

) pai

rs w

ith o

bjec

tsPr

oper

ty

Faci

litie

s fo

r sys

tem

wid

e na

me

of o

bjec

tsN

amin

g

Faci

litie

s fo

r atta

chin

g a

licen

se to

an

obje

ctLi

cens

ing

Faci

litie

s fo

r cre

atio

n, d

elet

ion,

cop

ying

, and

mov

ing

of o

bjec

tsLi

fe c

ycle

Faci

litie

s fo

r mar

shal

ing

and

unm

arsh

alin

g of

obj

ects

Exte

rnal

izat

ion

Adva

nced

faci

litie

s fo

r eve

nt-b

ased

asy

nchr

onou

s co

mm

unic

atio

nN

otifi

catio

n

Faci

litie

s fo

r asy

nchr

onou

s co

mm

unic

atio

n th

roug

h ev

ents

Even

t

Flat

and

nes

ted

trans

actio

ns o

n m

etho

d ca

lls o

ver m

ultip

le o

bjec

tsTr

ansa

ctio

n

Faci

litie

s to

allo

w c

oncu

rrent

acc

ess

to s

hare

d ob

ject

sC

oncu

rrenc

y

Faci

litie

s fo

r que

ryin

g co

llect

ions

of o

bjec

ts in

a d

ecla

rativ

e m

anne

rQ

uery

Faci

litie

s fo

r gro

upin

g ob

ject

s in

to li

sts,

que

ue, s

ets,

etc

.C

olle

ctio

n

Des

crip

tion

Serv

ice

Obj

ect I

nvoc

atio

n M

odel

s

Invo

catio

n m

odel

s sup

porte

d in

CO

RB

A.

Cal

ler c

ontin

ues

imm

edia

tely

an

d ca

n la

ter b

lock

unt

il re

spon

se is

del

iver

ed

At-m

ost-o

nce

Def

erre

d sy

nchr

onou

s

Cal

ler c

ontin

ues

imm

edia

tely

w

ithou

t wai

ting

for a

ny re

spon

se

from

the

serv

er

Best

effo

rt de

liver

yO

ne-w

ay

Cal

ler b

lock

s un

til a

resp

onse

is

retu

rned

or a

n ex

cept

ion

is

rais

ed

At-m

ost-o

nce

Sync

hron

ous

Des

crip

tion

Failu

re s

eman

tics

Req

uest

type

Even

t and

Not

ifica

tion

Serv

ices

(1)

The

logi

cal o

rgan

izat

ion

of su

pplie

rs a

nd c

onsu

mer

s of

eve

nts,

follo

win

g th

e pu

sh-s

tyle

mod

el.

Even

t and

Not

ifica

tion

Serv

ices

(2)

The

pull-

styl

e m

odel

for e

vent

del

iver

y in

CO

RB

A.

Mes

sagi

ng (1

)

CO

RB

A's

callb

ack

mod

el fo

r asy

nchr

onou

s met

hod

invo

catio

n.

Mes

sagi

ng (2

)

CO

RB

A'S

pol

ling

mod

el fo

r as

ynch

rono

us m

etho

d in

voca

tion.

Inte

rope

rabi

lity

GIO

P m

essa

ge ty

pes.

Part

(frag

men

t) of

a la

rger

mes

sage

Both

Frag

men

t

Con

tain

s in

form

atio

n on

an

erro

rBo

thM

essa

geEr

ror

Indi

catio

n th

at c

onne

ctio

n w

ill be

clo

sed

Both

Clo

seC

onne

ctio

n

Indi

cate

s cl

ient

no

long

er e

xpec

ts a

repl

yC

lient

Can

celR

eque

st

Con

tain

s lo

catio

n in

form

atio

n on

an

obje

ctSe

rver

Loca

teR

eply

Con

tain

s a

requ

est o

n th

e ex

act l

ocat

ion

of a

n ob

ject

Clie

ntLo

cate

Req

uest

Con

tain

s th

e re

spon

se to

an

invo

catio

nSe

rver

Rep

ly

Con

tain

s an

invo

catio

n re

ques

tC

lient

Req

uest

Des

crip

tion

Orig

inat

orM

essa

ge ty

pe

Clie

nts

Logi

cal p

lace

men

t of i

nter

cept

ors i

n C

OR

BA

.

Porta

ble

Obj

ect A

dapt

or (1

)

Map

ping

of C

OR

BA

obj

ect i

dent

ifier

s to

serv

ants

.a)

The

POA

supp

orts

mul

tiple

serv

ants

.b)

The

POA

supp

orts

a si

ngle

serv

ant.

Porta

ble

Obj

ect A

dapt

or (2

)

Cha

ngin

g a

C++

obj

ect i

nto

a C

OR

BA

obj

ect.

My_

serv

ant *

my_

obje

ct;

// D

ecla

re a

refe

renc

e to

a C

++ o

bjec

tC

OR

BA::O

bjec

tid_v

ar o

id;

// D

ecla

re a

CO

RBA

iden

tifie

r

my_

obje

ct =

new

MyS

erva

nt;

// C

reat

e a

new

C++

obj

ect

oid

= po

a ->

activ

ate_

obje

ct (m

y_ob

ject

);//

Reg

iste

r C++

obj

ect a

s C

OR

BA O

BJEC

T

Age

nts

CO

RB

A's

over

all m

odel

of a

gent

s, ag

ent s

yste

ms,

and

regi

ons.

Obj

ect R

efer

ence

s (1)

The

orga

niza

tion

of a

n IO

R w

ith sp

ecifi

c in

form

atio

n fo

r IIO

P.

Obj

ect R

efer

ence

s (2)

Indi

rect

bin

ding

in C

OR

BA

.

Cac

hing

and

Rep

licat

ion

The

(sim

plifi

ed) o

rgan

izat

ion

of a

DC

S.

Obj

ect G

roup

s

A p

ossi

ble

orga

niza

tion

of a

n IO

GR

for a

n ob

ject

gr

oup

havi

ng a

prim

ary

and

back

ups.

An

Exam

ple

Arc

hite

ctur

e

An

exam

ple

arch

itect

ure

of a

faul

t-tol

eran

t CO

RB

A sy

stem

.

Secu

rity

(1)

The

gene

ral o

rgan

izat

ion

for s

ecur

e ob

ject

invo

catio

n in

CO

RB

A.

Secu

rity

(2)

The

role

of s

ecur

ity in

terc

epto

rs in

CO

RB

A.

Ove

rvie

w o

f DC

OM

The

gene

ral o

rgan

izat

ion

of A

ctiv

eX, O

LE, a

nd C

OM

.

Obj

ect M

odel

The

diff

eren

ce b

etw

een

lang

uage

-def

ined

and

bin

ary

inte

rfac

es.

Tape

Lib

rary

and

Reg

istry

The

over

all a

rchi

tect

ure

of D

CO

M.

DC

OM

Ser

vice

s

Ove

rvie

w o

f DC

OM

serv

ices

in c

ompa

rison

to C

OR

BA

serv

ices

.

Non

eN

one

Tim

e

SSL,

Ker

bero

sAu

thor

izat

ion

Secu

rity

Dat

abas

e ac

cess

Non

eR

elat

ions

hip

Dat

abas

e ac

cess

Stru

ctur

ed s

tora

gePe

rsis

tenc

e

Activ

e D

irect

ory

Non

eTr

adin

g

Activ

e D

irect

ory

Non

ePr

oper

ty

Activ

e D

irect

ory

Mon

iker

sN

amin

g

-Sp

ecia

l cla

ss fa

ctor

ies

Lice

nsin

g

-C

lass

fact

orie

s, J

IT a

ctiv

atio

nLi

fe c

ycle

-M

arsh

alin

g ut

ilitie

sEx

tern

aliz

atio

n

-C

OM

+ Ev

ents

Not

ifica

tion

-C

OM

+ Ev

ents

Even

t

Dis

tribu

ted

Tran

sact

ion

Coo

rdin

ator

CO

M+

Auto

mat

ic T

rans

actio

nsTr

ansa

ctio

n

-Th

read

con

curre

ncy

Con

curre

ncy

-N

one

Que

ry

-Ac

tiveX

Dat

a O

bjec

tsC

olle

ctio

n

Win

dow

s 20

00 S

ervi

ceD

CO

M/C

OM

+ Se

rvic

eC

OR

BA

Ser

vice

Even

ts

Even

t pro

cess

ing

in D

CO

M.

Clie

nts

Pass

ing

an o

bjec

t ref

eren

ce in

DC

OM

with

cus

tom

mar

shal

ing.

Mon

iker

s (1)

Bin

ding

to a

DC

OM

obj

ect b

y m

eans

of f

ile m

onik

er.

Ret

urns

inte

rface

poi

nter

of o

bjec

t to

clie

ntM

onik

er7

Load

s its

sta

te fr

om fi

leO

bjec

t6

Inst

ruct

s ob

ject

to lo

ad p

revi

ousl

y st

ored

sta

teM

onik

er5

Cre

ates

obj

ect a

nd re

turn

s in

terfa

ce p

oint

er to

m

onik

erC

lass

obj

ect

4

Load

s cl

ass

obje

ctSC

M3

Look

s up

ass

ocia

ted

CLS

ID a

nd in

stru

cts

SCM

to

cre

ate

obje

ctM

onik

er2

Cal

ls B

indM

onik

er a

t mon

iker

Clie

nt1

Des

crip

tion

Perf

orm

erSt

ep

Mon

iker

s (2)

DC

OM

-def

ined

mon

iker

type

s.

Ref

eren

ce to

an

obje

ct in

a re

mot

e pr

oces

sPo

inte

r mon

iker

Ref

eren

ce to

a m

onik

er in

a c

ompo

sitio

nIte

m m

onik

er

Ref

eren

ce to

a c

ompo

sitio

n of

mon

iker

sC

ompo

site

mon

iker

Ref

eren

ce to

a c

lass

obj

ect

Cla

ss m

onik

er

Ref

eren

ce to

an

obje

ct c

onst

ruct

ed fr

om a

UR

LU

RL

mon

iker

Ref

eren

ce to

an

obje

ct c

onst

ruct

ed fr

om a

file

File

mon

iker

Des

crip

tion

Mon

iker

type

Act

ive

Dire

ctor

y

The

gene

ral o

rgan

izat

ion

of A

ctiv

e D

irect

ory.

Faul

t Tol

eran

ce

Tran

sact

ion

attri

bute

val

ues f

or D

CO

M o

bjec

ts.

Nev

er jo

in a

tran

sact

ion,

eve

n if

told

to d

o so

DIS

ABLE

D

Nev

er jo

in a

tran

sact

ion

NO

T_SU

PPO

RTE

D

Join

a tr

ansa

ctio

n on

ly if

cal

ler i

s al

read

y pa

rt of

one

SUPP

OR

TED

A ne

w tr

ansa

ctio

n is

sta

rted

if no

t alre

ady

done

so

REQ

UIR

ED

A ne

w tr

ansa

ctio

n is

alw

ays

star

ted

at e

ach

invo

catio

nR

EQU

IRES

_NEW

Des

crip

tion

Attr

ibut

e va

lue

Dec

lara

tive

Secu

rity

(1)

Aut

hent

icat

ion

leve

ls in

DC

OM

.

Auth

entic

ate,

inte

grity

-che

ck, a

nd e

ncry

pt d

ata

pack

ets

PAC

KET_

PRIV

ACY

Auth

entic

ate

data

pac

kets

and

do

inte

grity

che

ckPA

CKE

T_IN

TEG

RIT

YAu

then

ticat

e al

l dat

a pa

cket

sPA

CKE

TAu

then

ticat

e cl

ient

at e

ach

invo

catio

nC

ALL

Auth

entic

ate

clie

nt w

hen

first

con

nect

ed to

ser

ver

CO

NN

ECT

No

auth

entic

atio

n is

requ

ired

NO

NE

Des

crip

tion

Aut

hent

icat

ion

leve

l

Dec

lara

tive

Secu

rity

(2)

Impe

rson

atio

n le

vels

in D

CO

M.

The

serv

er c

an in

voke

rem

ote

obje

cts

on b

ehal

f of t

he c

lient

DEL

EGAT

E

The

serv

er c

an in

voke

loca

l obj

ects

on

beha

lf of

the

clie

ntIM

PER

SON

ATE

The

serv

er k

now

s th

e cl

ient

and

can

do

acce

ss c

ontro

l ch

ecks

IDEN

TIFY

The

clie

nt is

com

plet

ely

anon

ymou

s to

the

serv

erAN

ON

YMO

US

Des

crip

tion

Impe

rson

atio

n le

vel

Prog

ram

mat

ic S

ecur

ity

a)D

efau

lt au

then

ticat

ion

serv

ices

supp

orte

d in

DC

OM

.b)

Def

ault

auth

oriz

atio

n se

rvic

es su

ppor

ted

in D

CO

M.

(b)

Auth

oriz

atio

n us

ing

DEC

Priv

ilege

Attr

ibut

e C

ertif

icat

es (P

ACs)

DC

E

Auth

oriz

atio

n ba

sed

on th

e cl

ient

's id

entit

yN

AME

No

auth

oriz

atio

nN

ON

E

Des

crip

tion

Serv

ice

(a)

Kerb

eros

aut

hent

icat

ion

GSS

_KER

BER

OS

Win

dow

s N

T se

curit

yW

INN

T

DEC

aut

hent

icat

ion

base

d on

pub

lic k

eys

DC

E_PU

BLIC

DC

E au

then

ticat

ion

base

d on

sha

red

keys

DC

E_PR

IVAT

E

No

auth

entic

atio

nN

ON

E

Des

crip

tion

Serv

ice

Glo

be O

bjec

t Mod

el (1

)

The

orga

niza

tion

of a

Glo

be d

istri

bute

d sh

ared

obj

ect.

Glo

be O

bjec

t Mod

el (2

)

The

gene

ral o

rgan

izat

ion

of a

loca

l obj

ect f

or

dist

ribut

ed sh

ared

ob

ject

s in

Glo

be.

Glo

be O

bjec

t Mod

el (3

)

Inte

rfac

es im

plem

ente

d by

the

sem

antic

s sub

obje

ct o

f a

Glo

beD

oc o

bjec

t.

Rep

lace

the

cont

ent o

f an

entir

e do

cum

ent

PutA

llCon

tent

Rep

lace

the

cont

ent o

f an

elem

ent w

ith a

giv

en a

rray

of b

ytes

PutC

onte

nt

Ret

urn

the

cont

ent o

f an

elem

ent a

s an

arra

y of

byt

esG

etC

oten

t

Des

crip

tion

Met

hod

Con

tent

Inte

rfac

e

Ret

urn

a re

fere

nce

to th

e ro

ot e

lem

ent

Get

Roo

t

Set t

he ro

ot e

lem

ent

SetR

oot

Ret

urn

a lis

t of t

he e

lem

ents

cur

rent

ly in

the

docu

men

tAl

lEle

men

ts

Rem

ove

an e

lem

ent f

rom

the

Web

doc

umen

tD

elet

eEle

men

t

Add

an e

lem

ent t

o th

e cu

rrent

set

of e

lem

ents

AddE

lem

ent

Des

crip

tion

Met

hod

Doc

umen

t Int

erfa

ce

Glo

be O

bjec

t Mod

el (4

)

Inte

rfac

es im

plem

ente

d by

the

sem

antic

s su

bobj

ect o

f a G

lobe

Doc

Obj

ect.

Get

a li

st o

f ele

men

ts th

at a

re c

urre

ntly

che

cked

out

Get

Che

cked

Elem

ents

Che

ck in

a s

erie

s of

mod

ified

ele

men

tsC

heck

InEl

emen

ts

Che

ck o

ut a

ser

ies

of e

lem

ents

that

requ

ire m

odifi

catio

nC

heck

Out

Elem

ents

Des

crip

tion

Met

hod

Lock

Inte

rfac

e

Prov

ide

a lis

t of (

attri

bute

, val

ue)-p

airs

for a

n el

emen

tSe

tPro

perti

es

Ret

urn

the

list o

f (at

tribu

te, v

alue

)-pai

rs o

f an

elem

ent

Get

Prop

ertie

s

Des

crip

tion

Met

hod

Prop

erty

Inte

rfac

e

Proc

ess-

to-O

bjec

t Bin

ding

Bin

ding

a p

roce

ss to

an

obje

ct in

Glo

be.

Glo

be S

ervi

ces

Ove

rvie

w o

f pos

sibl

e G

lobe

impl

emen

tatio

ns o

f typ

ical

di

strib

utes

-sys

tem

s ser

vice

s.

Yes

Impl

emen

ted

per o

bjec

t com

bine

d w

ith fa

ult-t

oler

ant s

ervi

ces

Faul

t tol

eran

ce

Yes

Impl

emen

ted

on a

per

-obj

ect b

asis

Rep

licat

ion

Yes

Impl

emen

ted

per o

bjec

t, co

mbi

ned

with

(loc

al) s

ecur

ity s

ervi

ces

Secu

rity

Yes

Impl

emen

ted

on a

per

-obj

ect b

asis

Pers

iste

nce

No

Sepa

rate

ser

vice

, im

plem

ente

d by

a c

olle

ctio

n of

dire

ctor

y ob

ject

sPr

oper

ty/T

radi

ng

Yes

Sepa

rate

ser

vice

, im

plem

ente

d by

a c

olle

ctio

n of

nam

ing

obje

cts

Nam

ing

No

Impl

emen

ted

by e

ach

obje

ct s

epar

atel

yLi

cens

ing

Yes

Sepa

rate

cla

ss o

bjec

ts c

ombi

ned

with

per

-obj

ect i

mpl

emen

tatio

nsLi

fe c

ycle

Yes

Each

obj

ect i

mpl

emen

ts it

s ow

n m

arsh

alin

g ro

utin

esEx

tern

aliz

atio

n

No

Sepa

rate

obj

ect p

er g

roup

of e

vent

s (a

s in

DC

OM

)Ev

ent/N

otifi

catio

n

No

Sepa

rate

obj

ect r

epre

sent

ing

a tra

nsac

tion

man

ager

Tran

sact

ion

No

Each

obj

ect i

mpl

emen

ts it

s ow

n co

ncur

renc

y co

ntro

l stra

tegy

Con

curre

ncy

No

Sepa

rate

obj

ect t

hat h

olds

refe

renc

es to

oth

er o

bjec

tsC

olle

ctio

n

Ava

ilabl

ePo

ssib

le Im

plem

enta

tion

in G

lobe

Serv

ice

Com

mun

icat

ion

Invo

king

an

obje

ct in

Glo

be th

at u

ses a

ctiv

e re

plic

atio

n.

Glo

be S

erve

r

Ope

ratio

ns o

n a

Glo

be o

bjec

t ser

ver.

Get

the

stat

us o

f a s

peci

fic lo

cal o

bjec

tSt

atLR

Ret

urns

a li

st o

f all

loca

l obj

ects

for a

giv

en o

bjec

tsLi

stD

SOR

etur

ns a

list

of a

ll lo

cal o

bjec

tsLi

stAl

lLe

ts th

e se

rver

rem

ove

all l

ocal

obj

ects

of a

giv

en o

bjec

tU

nbin

dDSO

Lets

the

serv

er re

mov

e a

loca

l obj

ect o

f a g

iven

obj

ect

Rem

oveL

RLe

ts th

e se

rver

cre

ate

a lo

cal o

bjec

t for

a n

ew d

istri

bute

d ob

ject

Cre

ateL

RLe

ts th

e se

rver

bin

d to

an

obje

ct, e

ven

if it

is a

lread

y bo

und

AddB

indi

ngLe

ts th

e se

rver

bin

d to

a g

iven

obj

ect,

unle

ss it

is a

lread

y bo

und

Bind

Des

crip

tion

Met

hod

Obj

ect R

efer

ence

s and

Con

tact

Add

ress

es (1

)

The

repr

esen

tatio

n of

a p

roto

col l

ayer

in a

stac

ked

cont

act a

ddre

ss.

Ref

eren

ce to

a fi

le in

a c

lass

repo

sito

ryIm

plem

enta

tion

hand

leA

prot

ocol

-spe

cific

add

ress

Prot

ocol

add

ress

A co

nsta

nt re

pres

entin

g a

(kno

wn)

pro

toco

lPr

otoc

ol id

entif

ier

Des

crip

tion

Fiel

d

Obj

ect R

efer

ence

s and

Con

tact

Add

ress

es (2

)

The

repr

esen

tatio

n of

an

inst

ance

con

tact

add

ress

.

Strin

g th

at is

use

d to

initi

aliz

e an

impl

emen

tatio

nIn

itial

izat

ion

strin

g

Ref

eren

ce to

a fi

le in

a c

lass

repo

sito

ryIm

plem

enta

tion

hand

le

Des

crip

tion

Fiel

d

Glo

be N

amin

g Se

rvic

e

Itera

tive

DN

S-ba

sed

nam

e re

solu

tion

in G

lobe

.

Rep

licat

ion

(1)

The

inte

rfac

e of

the

repl

icat

ion

subo

bjec

t as

mad

e av

aila

ble

to th

e co

ntro

l sub

obje

ct.

Indi

cate

that

the

invo

catio

n on

the

sem

antic

s ob

ject

has

com

plet

edIn

voke

dPa

ss th

e m

arsh

aled

invo

catio

n re

ques

t to

the

repl

icat

ion

subo

bjec

tSe

ndIn

dica

te th

at a

new

met

hod

invo

catio

n ha

s be

en lo

cally

requ

este

dSt

art

Des

crip

tion

Met

hod

Rep

licat

ion

(2)

The

beha

vior

of t

he c

ontro

l su

bobj

ect a

s a fi

nite

stat

e m

achi

ne.

Exam

ples

of R

eplic

atio

n in

Glo

be (1

)

Stat

e tra

nsiti

ons a

nd a

ctio

ns fo

r act

ive

repl

icat

ion.Nex

t sta

teM

etho

d ca

llA

ctio

n to

take

Stat

e

STAR

TN

one

Ret

urn

resu

lts to

cal

ler

RET

UR

N

RET

UR

NIn

voke

din

voke

loca

l met

hod

INVO

KE

INVO

KESe

ndPa

ss m

arsh

aled

invo

catio

nsSE

ND

SEN

DSt

art

Non

eST

ART

Mod

ify m

etho

d

STAR

TN

one

Ret

urn

resu

lts to

cal

ler

RET

UR

N

RET

UR

NIn

voke

dIn

voke

loca

l met

hod

INVO

KE

INVO

KESt

art

Non

eST

ART

Nex

t sta

teM

etho

d ca

llA

ctio

n to

take

Stat

e

Rea

d m

etho

d

Exam

ples

of R

eplic

atio

n in

Glo

be (2

)

Stat

e tra

nsiti

ons a

nd a

ctio

ns w

ith p

rimar

y-ba

ckup

repl

icat

ion.

STAR

TN

one

Ret

urn

resu

lts to

cal

ler

RET

UR

N

RET

UR

NIn

voke

din

voke

loca

l met

hod

INVO

KE

Nex

t sta

teM

etho

d ca

llA

ctio

n to

take

Stat

eIN

VOKE

Star

tno

neST

ART

Mod

ify m

etho

d at

prim

ary

repl

ica

Nex

t sta

teM

etho

d ca

llA

ctio

n to

take

Stat

e

STAR

TN

one

Ret

urn

resu

lts to

cal

ler

RET

UR

N

RET

UR

NSe

ndPa

ss m

arsh

aled

invo

catio

nSE

ND

SEN

DSt

art

Non

eST

ART

Mod

ify m

etho

d at

bac

kup

repl

ica

STAR

TN

one

Ret

urn

resu

lts to

cal

ler

RET

UR

N

RET

UR

NIn

voke

dIn

voke

loca

l met

hod

INVO

KE

INVO

KESt

art

Non

eST

ART

Nex

t sta

teM

etho

d ca

llA

ctio

n to

take

Stat

eR

ead

met

hod

Secu

rity

(1)

The

posi

tion

of a

secu

rity

subo

bjec

t in

a G

lobe

loca

l obj

ect.

Secu

rity

(2)

Usi

ng K

erbe

ros t

o es

tabl

ish

secu

re d

istri

bute

d sh

ared

ob

ject

s.

Sum

mar

y (1

)

Com

paris

on o

f CO

RB

A, D

CO

M, a

nd G

lobe

.

No

No

yes

Trad

ing

serv

ice

No

Yes

Yes

Dire

ctor

y se

rvic

e

Obj

ect d

epen

dent

Har

d-co

ded

Flex

ible

(PO

A)O

bjec

t ser

ver

No

Yes

Yes

Mes

sagi

ng

No

Yes

Yes

Even

ts

No

Yes

Yes

Cal

lbac

ks

No

Yes

Yes

Asyn

c. c

omm

unic

atio

n

Yes

Yes

Yes

Sync

. com

mun

icat

ion

Bina

ryBi

nary

IDL

base

dIn

terfa

ces

Few

From

env

ironm

ent

Man

y of

its

own

Serv

ices

Dis

tribu

ted

obje

cts

Rem

ote

obje

cts

Rem

ote

obje

cts

Obj

ect m

odel

Scal

abilit

yFu

nctio

nalit

yIn

tero

pera

bilit

yD

esig

n go

als

Glo

beD

CO

MC

OR

BA

Issu

e

Con

tinue

d �

Sum

mar

y (2

)

Com

paris

on o

f CO

RB

A, D

CO

M, a

nd G

lobe

.

Glo

beD

CO

MC

OR

BA

Issu

e

Mor

e w

ork

need

edVa

rious

mec

hani

sms

Vario

us m

echa

nism

sSe

curit

y

No

By tr

ansa

ctio

nsYe

sR

ecov

ery

supp

ort

By re

plic

atio

nBy

tran

sact

ions

By re

plic

atio

nFa

ult t

oler

ance

No

Yes

Yes

Tran

sact

ions

Sepa

rate

sub

obje

ctN

one

Sepa

rate

ser

ver

Rep

licat

ion

supp

ort

Onl

y in

tra-o

bjec

tTr

ansa

ctio

nsTr

ansa

ctio

nsSy

nchr

oniz

atio

n

True

iden

tifie

rIn

terfa

ce p

oint

erO

bjec

t's lo

catio

nO

bjec

t ref

eren

ce

Yes

No

No

Loca

tion

serv

ice

Yes

Yes

Yes

Nam

ing

serv

ice