Wilamowski B.M., Irwin J.D. The Industrial Electronics Handbook. Second Edition: Industrial Communication Systems

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Industrial Internet 56-5

about.events.generated.in.the.automation.layer..Typically,.event.sources.in.the.eld.layer.or.the.sensor/

actuator

.lay

.are.usi

.di

erent

.tec

hniques,

.add

ressing

.the.rea

l-time

.con

straints,

.and.the.imp

lemen-

tation

.eo

.(e.

g.,

.mai

.se

rvers

.ne

.a.lo

.of.re

sources).

.add

ition,

.oth

.pro

tocols

.lik

.Fil

.Tra

nsfer

.Pro

tocol

.(FT

.[FT

P85]

.and.its.der

ivates

.are.qui

.oe

use

.to.tra

nsfer

.bin

ary

.dat

.bet

ween

.cli

ent

.and.ser

ver.

.In.Ind

ustrial

.Int

ernet,

.suc

.app

lications

.are.use

ful

.in.the.upp

.lay

ers

.dow

.to.the.auto

mation

.lay

.or.eve

.the.el

.lay

er.

.For.exa

mple,

.hug

.dat

.set

in.bat

.sys

tems,

.lar

.arc

hives,

.pro

grams,

.or.par

ameter

.dat

.are.tra

nsferred

.usin

.FTP

-like

.pro

tocols.

Esp

ecially

.in.sys

tems

.whe

.Ind

ustrial

.Ethe

rnet

.is.use

.at.the.el

.lay

er,

.FTP

-based

.sol

utions

.are.eas

to.im

plement.

56.3.1.1

Hyp

text tran

sfer Protocol

HyperText

.Tra

nsfer

.Prot

ocol

.(HT

TP)

.[HT

TP99]

.is.the.mos

.com

monly

.kno

.tra

nsport

.rel

ated

.pro

tocol,

used.in.any.Web.app

lication

.to.con

nect

.bet

ween

.Web.bro

wser

.and.Web.serv

er.

.HTT

.is.a.sta

teless

.pro

tocol.

. e.bro

wser

.act

.as.a.cli

ent

.and.inv

okes

.the.req

uest

.(ty

pically

.via.HTT

P-GET

.met

hod),

.the.serv

res

ponds

.wit

.the.doc

ument

.req

uested

.or.wit

.an.err

.mes

sage.

.Bes

ides

.HTT

P-GET,

.oth

.met

hods

.can.

be.used.to.tra

nsfer

.the.hea

der

.of.the.doc

ument

.onl

.(HT

TP-HEAD)

.or—

.imp

lemented

.at.the.serv

er—to

upl

oad

.doc

uments

.(HT

TP-PUT).

. e.met

hod

.HTT

P-POST

.is.wid

ely

.used.for.the.tra

nsfer

.of.for

.dat

fro

.cli

ent

.to.serv

.and.for.inv

oking

.app

lication

.log

.at.the.serv

er.

. e.HTT

.pro

tocol

.[HT

TPS0]

.is.a.

secur

.ver

sion

.of.HTT

.oe

.com

bined

.wit

.oth

.secur

ity

.met

hods

.at.serv

.and

/or

.cli

ent.

.application.of.HTTP.in.Industrial.Internet.requires.a.Web.server.at.the.component.acting.as.the.

ser

ver.

. e.gre

.var

iety

.of.ava

ilable

.Web.ser

ver

.imp

lementations

.for.di

erent

.pur

pose—ranging

.fro

hig

h-end,

.hig

h-load

.ser

ver

.so

ware

.lik

.Apa

che

.Web.Ser

ver

.or.Mic

roso

.Int

ernet

.Inf

ormation

.Ser

ver

(II

.dow

.to.embe

dded

.Web.ser

vers

.wit

.mem

ory

.foo

tprint

.of.onl

.a.few.kil

obytes—enables

.a.wid

ran

.of.app

lications.

.How

ever,

.it.has.to.be.con

sidered

.tha

.the.typ

ical

.com

munication

.par

adigm

.is.pur

cli

ent–server.

. is.mea

.tha

.tra

nsfer

.alw

ays

.sta

rts

.upo

.cli

ent

.ini

tiative.

.HTT

.in.its.basi

.for

.is.

pro

blematic

.to.tr

ansfer

.ev

ents,

.sin

.a.cl

ient

.wo

uld

.ha

.to.po

.th

.se

rver

.al

.th

.ti

me.

56.3.1.2

Simp

le Network Management Protocol

Developed

.for.net

work

.man

agement

.fun

ctions,

.SNM

.[SN

MP90]

.rea

lizes

.the.com

munication

.mod

and.the.inf

ormation

.mod

.par

.of.OSI.net

work

.man

agement.

.Desi

gned

.to.be.simp

.to.use.and.to.

imp

lement,

.SNM

.has.bec

ome

.the.de.fac

.sta

ndard

.for.net

work

.man

agement.

. e.com

munication

mod

.par

.of.SNM

.can.als

.be.use

.as.a.tra

nsport

.pro

tocol.

.It.rel

ies

.on.the.UDP.of.the.TCP

/IP

.pro

tocol

.sui

te.

.Besi

des

.met

hods

.for.rea

ding

.att

ributes

.of.man

aged

.obje

cts

.lik

.SNM

P-GET,

.SNM

P-GET-

NEXT,

.or.SNM

P-GET-BULK,

.the.pro

tocol

.als

.pro

vides

.SNM

P-SET

.to.set.val

ues

.of.man

aged

.obje

cts.

Add

itionally,

.SNM

.pro

vides

.TRA

.met

hods

.to.tra

nsfer

.eve

nts

.occ

urring

.in.man

aged

.obje

cts

.of.an.

age

.to.the.cor

responding

.man

ager.

.In.con

trast

.to.cli

ent–server

.par

adigms,

.thi

.met

hod

.can.be.use

.to.

pro

pagate

.ev

ents

.wi

thin

.a.sy

stem

.wi

thout

.cl

ient

.in

itiative.

Especially,

.the.TRA

.met

hod

.mak

.SNM

.sui

table

.as.a.tra

nsport

.pro

tocol

.for.ind

ustrial

.app

lications.

Aut

omation

.sys

tems

.usi

.Ind

ustrial

.Eth

ernet

.typ

ically

.pro

vide

.SNM

.imp

lementations

.for.the.man

age-

ment

.of.the.net

work-related

.inf

ormation.

.How

ever,

.the.ful

.int

egration

.of.ind

ustrial

.solu

tions

.int

.net

work

man

agement

.app

lication

.req

uires

.usi

.of.the.SNM

.inf

ormation

.mod

el—the

.man

agement

.inf

ormation

base.(MI

.for.desc

ription

.of.com

ponents—as

.wel

.as.the.int

egration

.of.the.fun

ctional

.mod

.int

.SNM

app

lications.

. is.is.rat

her

.di

cult,

.sin

.bot

.fol

low

.app

roaches

.di

erent

.fro

.tho

.cur

rently

.avai

lable

in.ind

ustrial

.app

lications.

. e.use.of.SNM

.as.a.tra

nsport

.lay

.onl

.for.exa

mple,

.for.ind

ustrial

.Web.

app

lications,

.is.pos

sible

.wit

.lim

ited

.eo

rt.

56.3.1.3

Web S

ervices Using Simple Object

acce

ss Protocol

.ord

.to.inv

oke

.fun

ctions

.of.a.ser

ver

.via.the.net

work,

.di

erent

.sys

tems

.hav

.bee

.dev

eloped.

. ey.

ran

.fro

.ope

.com

plex,

.ful

.fea

tured

.sol

utions

.lik

.Com

mon

.Obje

.Req

uest

.Bro

ker

.Arc

hitectures

(CO

RBA)

. [CO

RBA]

. to. pro

prietary

. spe

cications

. lik

. Mic

roso’s

. Dis

tributed

. Com

ponent

. Obje

56-6 Industrial Communication Systems

Model.(DCOM).[RGR97].or.the.transport.layer.of.the.NET.specication..However,.due.to.complex-

ity,

.management.eort,.and.security.reasons,.a.much.simpler.solution.was.requested.. e.Simple.

Object.Access.Protocol.(SOAP).[DBX00].was.dened.to.overcome.the.limitations.and.to.provide.a.

“rewall-friendly”.way.of.invoking.functions..SOAP.is.a.protocol.that.can.be.bound.to.several.under-

lying

.transport.layers,.including.HTTP.and.SMTP.. e.functions.calls,.the.responses,.and.possible.

error.messages.are.serialized.in.coded.format.using.eXtended.Markup.Language.(XML).and.are.then.

embedded.into.the.transport.protocol.

Depending

.on.the. implementation.(see.Figure.56.5),.a.listener.function.is.invoked.by.the.trans-

port

.layer,.a.Web.server.or.a.stand-alone.application,.e.g.,.the.service.request.is.passed.to.the.listener,.

the.function.called.and.the.arguments.provided.by.the.call.are.passed.to.business.logic.components..

 ey.nally.provide.the.data.for.response.and.issue.its.transfer.to.the.client.. e.services.provided.by.

a.Web.service.server.are.described.using.a.service.description.following.the.denitions.in.Web.Service.

Description.Language.(WSDL),.an.XML-based.format.[WSD01].

Application

.of.Web.services.in.industrial.applications.is.steadily.growing..Because.of.the.publicly.

available.transport.protocols.Web.services.can.be.bound.to,.Web.services.provide.an.easy.and.com-

monly

.accepted.way.of.handling.communication.between.applications.on.dierent.components.and.

perhaps.dierent.operating.systems.

56.3.2 technologies for Information Description and Presentation

56.3.2.1 Hypertext Markup Language

.content.transferred.by.Internet.technologies.is.manifold..Besides.binary.data.representations.for.

dierent.formats.and.coding,.technologies.for.information.descriptions.have.been.developed.. e.most.

important.technology.in. this.area.is. without.any.doubt.the. HyperText.Markup.Language.(HTML).

[HTM00],.the.main.description.technology.of.the.World.Wide.Web..A.client,.a.Web.browser,.inter-

preting

.the.HTML.statements.of.a.hypertext.document.and.thus.rendering.and.presenting.the.content.

described.in.HTML.documents.is.available.on.nearly.every.platform..Together.with.presentation-related.

technologies.like.Cascading.Style.Sheets.(CSS).[CSS98],.complex.solutions.for.display.of.dierent.types.

of.data.have.become.state.of.the.art.

HTML

.documents.can.be.used.for.any.functions.in.automation.domain.that.need.to.display.data—

especially

.data.from.dierent.sources.in.dierent.formats..In.any.case,.the.data.are.provided.by.the.

server.upon.client.request.. is.might.be.dicult.for.some.data.sources.(events).

Service request

Service response

Service control

Web service

Listener

Business

logic

Data

access

Data

Device

data

Meta-

infor-

mation

FIGURE 56.5 Principle.structure.of.a.Web.service.server.

Industrial Internet 56-7

56.3.2.2 eXtensible Markup Language

HTML

.has.limitations.concerning.its.mixture.of.presentation-related.and.content-related.markup..In.

order.to.separate.the.content.from.its.presentation,.the.XML.has.been.specied.[TBR98]..XML.was.

developed.and.established.as.a.markup.language.for.generic.purpose..XML.is.oen.treated.as.a.Meta.

language.suitable.for.development.of.customized,.specic.languages.

XML

.expands.the.description.language.HTML.with.user-dened.tags,.data.types,.and.structures..

Furthermore,.it.addresses.one.of.the.limitations.in.HTML—it.introduces.a.clear.separation.between.the.

data.descriptions,.the.data.themselves,.and.their.representation.(Figure.56.6)..For.declaring.syntactical.

information,.a.separate.denition.le.XML.Schema.Denition.Language.(XSD).[XSD01].or.Document.

Type.Denition.(DTD).is.used.. is.allows.reusing.the.description.structure.in.dierent.contexts.. is.

provides.a.number.of.benets.when.using.the.same.XML.description.le.for.dierent.tasks..In.combi-

nation

.with.Namespace.denitions.semantics.can.be.dened..Namespaces.allow.establishing.a.clear.

relation.between.tags.dened.in.a.schema.and.their.usage.context.

.availability. of. a. wide.range. of.soware. tools. allows.creating.eective.XML-based. solutions..

Publicly.available.solutions.for.parsers.and.development.frameworks.supporting.dierent.platforms.and.

dierent.operating.systems.contribute.to.the.actual.hype.of.using.XML.as.a.general-purpose.descrip-

tion

.language.. e.XML.data.can.be.ltered.and.associated.to.soware.. e.selection.of.the.necessary.

information.and.the.denition.of.their.presentation.details.can.be.performed.by.means.of.scripts.and.

style.sheets.. e.style.sheets.[FBO98].are.part.of.the.development.of.XML..In.most.cases,.they.are.

implemented.using.the.eXtensible.Style.Language.for.Transformation.(XSLT)..An.XML.document.can.

be.related.to.dierent.style.sheets.for.dierent.presentation.or.conversion.functions,.so.that.only.the.

XSLT.references.have.to.be.changed..Since.style.sheets.in.XSLT.can.contain.script.elements,.a.Document.

Object.Model.(DOM).[DOM98].has.been.developed.to.support.scripting.. is.DOM.is.used.to.access.

the.XML.le.and.its.elements.from.a.script.. e.DOM.programming.objects.provide.interfaces.to.the.

original.XML.le,.representing.its.structure.as.a.tree.of.objects.. e.output.data.of.the.DOM.functions.

can.be.used.to.generate.any.textual.or.binary.les,.including.new.XML.les.with.a.dierent.structure..

 e.major.benet.of.this.solution.is.a.unique,.reusable.description.with.an.excellent.consistency.and.

reduced.eorts.of.the.description.process.

Applications

.of.XML.in.the.industrial.domain.have.developed.with.increasing.speed.. ey.cover.

static.descriptions.for.multiple.purposes,.for.example,.device.descriptions,.data.exchange.descriptions,.

and.protocol.descriptions.using.SOAP.and.WSDL.(e.g.,.OPC.and.XML.specication.[OPC04]).

.special.importance.for.visualization.tasks.is.assigned.to.Scalable.Vector.Graphics.(SVG).[SVG01],.

an.XML. format.for.presentation.of.two-dimensional.vector-based.graphics.including. functions. for.

<root>

<child_element attribute=“attr-value”>

</child_element>

<child_element>

<next_generation>

Value

</next_generation>

</child_element>

</element>

<child_element>

</child_element>

</element>

</root>

Style-sheet

(Formatting

instructions)

Document type

denition—DTD

Schema

(Syntax, Semantics)

XML-le

Output les

(Description

content)

FIGURE 56.6 Structure.of.an.XML.le.(le).and.the.XML.environment.

56-8 Industrial Communication Systems

scripting.of.the.elements..Browsers.can.use.plug-ins.for.rendering.and.display..Other.XML-based.

form

ats

.are.avai

lable

.for.use.in.mult

imedia

.appl

ications.

. ey.may.be.used.in.indu

strial

.appl

ications

when

ever

.the

.bec

ome

.sta

ndards

.and.the.sup

port

.by.tool

.is.sta

ble.

56.3.3 technologies for Server-Side and Client-Side Functions

 e.functionality.of.combining.content.description,.application-depending.interpretation,.and.trans-

port

.is.prov

ided

.at.both.the.serv

.side.and.at.the.clie

nt.

.Die

rent

.tech

nologies

.have.been.deve

loped.

Popu

lar

. clie

nt-based

. solu

tions

. are—

without

. maki

. any. clai

. to. be. comp

lete—JavaScript,

. Java

Applets,

. Acti

veX-Controls,

. and. Flas

. ey. requ

ire

. clie

nt-based

. runt

ime

. envi

ronments,

. like. Java.

Virt

ual

.Mach

ine

.(JVM

.Flas

.Play

ers,

.and.alik

. ey.migh

.be.avai

lable

.bund

led

.with.the.clie

.so-

are

.(e.

g.,

.a.brow

ser),

.or.may.req

uire

.ins

tallation

.of.plu

g-ins.

.An.inte

resting

.and.rapi

dly

.used.app

roach

is.Asyn

chronous

.Java

script

.and.XML.(AJA

X),

.whic

.allo

.high

.inte

ractive

.appl

ications

.with.auto-

atically,

.dyn

amically

.loa

ding

.and.ren

dering

.of.inf

ormation

.fra

gments.

Well-known

.serv

er-based

.tech

nologies

.incl

ude

.PHP,.Java

-Servlets,

.Acti

.Serv

.Page

.(ASP

.and.

Comm

.Gate

way

.Inte

rface

.(CGI

.In.this.case

.the.serv

.comp

onent

.requ

ires

.the.runt

ime

.envi

ron-

ment,

.for.exam

ple,

.scri

pting

.engi

nes

.or.serv

let

.cont

ainers.

. e.latt

.are.oen.bund

led

.with.Web.serv

ers;

.Apa

che

.Tom

cat

.is.an.exa

mple.

Applications

.of.clie

nt-

.and.serv

er-side

.tech

nologies

.in.the.indu

strial

.doma

.can.be.comp

ared

.to.stan

dard

.IT-b

ased

.solu

tions.

. ey.are.as.mani

fold

.as.the.tech

nologies

.supp

orted.

.Depe

nding

.on.the.use.case

a.comb

ination

.of.die

rent

.tech

nologies

.may.be.requ

ired.

.Addi

tional

.cons

traints

.may.be.deri

ved

.con-

erning

.real

-time

.aspe

cts,

.data.cons

istency,

.and.data.and.inte

rface

.manag

ement.

.Typi

cally,

.gate

ways

.to.

unde

rlying

.leve

.of.the.auto

mation

.pyra

mid

.(see.Chap

ter

.13).are.impl

emented

.at.the.serv

.comp

onents.

.impo

rtant

.feat

ure

.for.sele

ction

.of.a.serv

er-

.or.clie

nt-side

.tech

nology

.in.the.indu

strial

.appl

ication

area.is.its.matu

rity,

.oen.trea

ted

.as.a.combi

nation

.of.time.of.avai

lability,

.stan

dardization,

.tool.supp

ort,

etc..Taking.into.account.the.typical.life.cycles.of.automation.systems.ranging.from.3.to.5.years.in.factory.

autom

ation

.to.more.than.40.year

.in.proc

ess

.autom

ation

.and.powe

.plan

ts,

.newl

.intr

oduced

.tech

nolo-

gies

.are.hesi

tantly

.app

lied.

56.4 application Examples

 e.application.of.Internet.technologies.in.Industrial.automation.depends.on.the.specic.use.cases..

 ese.use.case

.also.den

.the.crit

eria

.for.tech

nology

.sele

ction.

. us,.the.appl

ication

.rang

.beco

mes

broa

der

.and.broa

der.

.Witho

.clai

ming

.comp

leteness,

.some.of.the.typi

cal

.appl

ication

.exam

ples

.are.

desc

ribed

.in.thi

.sec

tion.

56.4.1 Description technologies

Device.descriptions.like.Electronic.Device.Description.(EDD).[IEC07].became.more.and.more.impor-

tant

.for.many. appl

ications

. in. indu

strial

.autom

ation,

.espe

cially

.in. engi

neering

.and. netw

ork

.set-

up,

but.not.limi

ted

.to..Toge

ther

.with.the.evol

ving

.func

tional

.comp

lexity

.of.eld.devi

ces

.the.desc

ription

lang

uages

.had.to.be.adapt

.in.orde

.to.ree

.all.the.feat

ures

.of.devi

ces.

. ey.typi

cally

.requ

ire

.spe-

ic

.pars

ers

.and.inte

rpreters

.for.inte

gration

.into.appl

ications.

. ese.pars

ers

.and.inte

rpreters

.have.to.

be.adapt

.as.well.upon.chan

ges

.of.the.desc

ription

.lang

uage.

.It.is.quit

.usua

.that.seve

ral

.pars

ers

.exis

with

.one.app

lication,

.all

owing

.to.sup

port

.a.bro

.ran

.of.el

.dev

ices

.and.di

erent

.net

works.

XML

.seem

.to.solv

.seve

ral

.of.the.prob

lems

.stat

.abov

.XML.as.a.meta.lang

uage

.is.inte

nded

.to.

be.used.for.the.den

ition

.of.spec

ic

.lang

uages—device

.desc

riptions

.are.an.exam

ple

.for.this

.Good.

qual

ity

.pars

ers

.and.sow

are

.tools.are.avai

lable

.and.can.be.easil

.inte

grated

.into.appl

ications.

.So.using.

an.XML-b

ased

.devi

.desc

ription

.woul

.redu

.impl

ementation

.eor

.at.the.appl

ication

.proc

essing

devi

.desc

riptions.

. us,.seve

ral

.acti

vities

.have.been.star

ted

.to.den

.XML-b

ased

.devi

.desc

riptions.

Industrial Internet 56-9

Although.with.ISO.15745.[ISO03].a.generic.approach.exists,.the.dierent.user.organizations.provided.

their.own.schemas.and.mappings.of.the.traditional.description.statements.to.XML.formats.(See.Figure.

56.7)..With.Field.Device.Conguration.Markup.Language.(FDCML).[FDC01],.a.suitable.description.

exists.not.only.for.InterBus-S,.but.also.for.Industrial.Ethernet-based.devices;.it.is.applicable.by.extension.

for.other.systems,.too.(for.example.CANopen).. e.Electronic.Data.Sheet.(EDS).for.DeviceNet.[EDS00].

is.based.on.XML.. e.Generic.Station.Description.Markup.Language.(GSDML).[GSD06].is.supporting.

PROFINET.IO.devices;.XML-based.formats.for.EDD.are.in.discussion.

.benets.of.XML.concerning.soware.tool.support,.exibility,.and.extensibility.have.been.proven.

by.several.applications..It.is.relatively.easy.to.generate.documents.like.catalog.data.sheets.or.user.inter-

faces

.for.visualization.from.existing.device. descriptions..However,. XML.also.has.some.drawbacks..

Because.of.the.mostly.long.XML.tags,.the.descriptions.become.quite.large.. is.may.lead.to.storage.

problems.. e.complexity.of.the.XML.schemas.may.lead.to.time-consuming.parsing.of.descriptions..

 e.number.of.existing.description.formats.will.produce.integration.eorts.again—even.if.the.same.

parsers.can.be.used..Since.this.is.not.a.technology.problem,.it.cannot.be.expected.that.XML.can.solve.

this—it.has.to.be.initiated.by.the.end.users.

Another

.typical.application.of.XML.is.description.of.dierent.content.that.will.be.processed.and/or.

displayed.in.applications.. e.exibility.of.XML.is.a.prerequisite.for.such.type.of.modeling,.especially.

when.other.Internet.technologies.are.implemented,.too..For.example,.a.Web.portal.for.maintenance.of.

machines.may.provide.dierent.types.of.data—dynamic.data.from.the.machine.components,.static.data.

like.description,.handbooks,.plans,.etc.. e.data.need.to.be.associated.together.depending.on.the.func-

tions

.the.portal.oers..It.is.not.challenging.to.collect.the.data,.but.the.assignment.has.to.be.performed.

at.a.higher.level.. is.assignment.depends.on.context,.for.example,.the.user.role,.the.communication.

features,.or.specic.phases.of.the.life.cycle.

Device_Prole

Device_Manager_Object

Application_Process_Object

ProfileRevision

ProfileName

ProfileSource

ProfileClassID

ProfileDate

AdditionalInformation

ProfileIdentification

Device_Identity_Object

Device_Function_Object

0..1

1..*

1..∞

0..∞

0..*

ProleBody

DeviceIdentity

DeviceManager

DeviceFunction

ApplicationProcess

nonStandardizedExtension

Attributes

ISO15745Reference_DataType

ISO15745Profile

IASInterfaceType

ISO15745Part

ISO15745Edition

ProleTechnology

ProfileBody

ProfilesBody

Document element

ProleHeader

ISO15745Reference

FIGURE 56.7 Mapping.of.device.model.acc..ISO.15745.to.the.FDCML.XML.schema.

56-10 Industrial Communication Systems

XML.not.only.provides.a.method.for.dening.the.relations,.but.also.for.context-dependent.lter-

ing

.and.access.. e.content.description.should.follow.a.model.dening.the.specic.requirements.for.

expressing.the.relations.. ese.can.be.modeled.as.specic.elements.of.the.XML.schema..Finally,.in.the.

description.les.the.relations.are.inserted.[WOL03]..Figure.56.8.shows.a.fragment.of.the.model.and.the.

mapping.toward.XML.

56.4.2 Browser-Based applications

Browser-based.applications.are.typically.used.for.visualization.purposes..Respective.solutions.can.be.

found.in.nearly.every.visualization-related.product.in.automation.. e.ability.to.cover.large.distances.

makes.such.solutions.especially.interesting.for.all.tasks.that.require.remote.access.to.the.automation.sys-

tem,

.for.example,.remote.maintenance..Instead.of.requiring.specic.protocol.installation,.only.TCP/IP.and.

the.above.mentioned.transport-related.protocols.like.HTTP.are.necessary,.a.Web.browser.on.the.client.

is.typically.also.available.. is.simplies.installation.and.maintenance.eorts.dramatically..However,.

the.browser.alone.is.not.always.sucient,.since.oen.complex,.animated.graphics.have.to.be.shown..

In.addition,.the.information.presented.has.to.be.enriched.with.dynamically.changing.data.from.the.

process.

Several

.solutions.are.available.to.solve.the.problem.sketched.above.. e.data.are.provided.by.gateways.

to.the.automation.system’s.components,.by.controllers,.databases,.or.by.using.standard.interfaces.like.OPC.

[OPC98].. e.transfer.of.the.data.can.be.done.using.HTTP.or.SNMP.. e.dynamic.parts.of.the.solutions.

can.be.realized.with.client-side.or.server-side.functions.using.technologies.mentioned.above..However,.the.

specic.solution.has.to.reect.the.requirements.adopted.from.the.use.cases..For.example,.a.requirement.

could.be.to.allow.access.from.clients.with.restricted.capabilities.in.communication.bandwidth.and.graphi-

cal

.resolution.of.the.display.like.mobile.phones.or.handhelds.. is.requires.personalization.of.the.data.to.

be.displayed..Another.topic.is.the.necessity.for.browser.plug-ins..For.example,.displaying.a.ash.animation.

or.SVG.content.requires.the.prior.installation.of.the.appropriate.plug-ins.. is.limits.the.general.applica-

bility

.of.such.a.solution..Furthermore,.an.installation.on-the-y.might.not.be.always.possible.because.of.

access.restrictions.and.insucient.user.rights.

Another

.important.topic.is.the.protection.of.intellectual.properties..If.client-side.scripting.is.used,.

for.example,.JavaScript,.the.scripts.need.to.be.downloaded.to.the.client’s.browser..Since.the.functions.are.

executed.within.the.browser’s.scripting.engine,.they.are.transferred.and.thus.are.available.at.source.

code.level..So.it.is.relatively.easy.to.modify.or.to.abuse.them..A.server-side.solution,.for.example,.using.

Plant

Machine

1..*

Parameter

Catalog

1..*

Menue

1..*

Documentation

1..*

External resource

<<has_parameters>>

<<has_doc>>

<<instance_of>>

<<has_resource>>

role=“HMI”

role=“Catalog”

<root>

<le>

<le><le>

<Menu>

<Menu>

<<has_menue>>

FIGURE 56.8 Mapping.of.a.Web.portal.content.description.model.to.a.(symbolic).XML.le.

Industrial Internet 56-11

PHP,.solves.this.problem..However,.it.requires.frequent.updates.of.the.content,.since.every.change.is.

mad

.at.the.ser

ver.

.Jav

.app

lets

.see

.to.sol

.par

.of.the.pro

blem,

.sin

.the

.are.tra

nsferred

.as.bin

ary

dat

.(cl

ass

.le

.fro

.pre

specied

.ser

vers,

.res

ide

.in.a.san

dbox

.wit

hin

.the.bro

wser’s

.vir

tual

.mac

hine,

but.can.use.sev

eral

.und

erlying

.tra

nsport

.mec

hanisms.

.But.aga

in,

.a.gen

eral

.sol

ution

.for.thi

.pro

blem

can

not

.be.giv

en.

Figure

.56.

.sho

.an.exa

mple

.for.a.bro

wser-based

.app

lication

.usin

.SVG.gra

phics

.wit

.ani

mation.

 e.nav

igation

.are

.are.cre

ated

.on.the.ser

ver

.wit

.PHP

.the.con

tent

.mod

.use

.XML

.and.the.SVG.

gra

phic

.is.cre

ated

.fro

.a.Com

puter-aided

.desi

.(CA

D)-drawing

.of.the.mac

hine

.[WO

L03].

. is.sho

the.ty

pical

.co

mbination

.of.di

erent

.In

ternet

.te

chnologies

.as.me

ntioned

.ab

ove.

56.4.3 Machine–Machine Communication Using Web Services

Besides.the.application.with.user.interfaces,.Internet.technologies.may.also.be.used.eectively.between.

dis

tributed

.app

lications.

. is.is.oe

.cal

led

.mac

hine–machine

.com

munication.

. e.app

lications

.nee

to.tra

nsfer

.dat

.or.to.inv

oke

.fun

ctions.

. us

.Web.ser

vices

.usin

.SOA

.as.the.tra

nsport

.pro

tocol

.wit

ser

vice

.des

criptions

.in.WSD

.are.the.mos

.pro

mising

.tec

hnology

.in.thi

.sce

nario.

.Sin

.thi

.con

cept

fol

lows

.the.act

ual

.tre

.of.ser

vice-oriented

.arc

hitectures

.(SO

.wit

.loo

sely

.cou

pled,

.dis

tributed

.fun

tions,

.man

.so

ware

.dev

elopment

.env

ironments

.sup

port

.the.pro

cess

.of.de

ning

.and.imp

lementing

.the.

app

ropriate

.so

ware

.com

ponents.

.For.exa

mple,

.Mic

roso’s

.Vis

ual

.Stu

dio

.and.Ecl

ipse

.pro

vide

.fun

tions

.to.de

.WSD

.le

.to.gen

erate

.ser

vice

.com

ponents

.or.cli

ents.

. ey.han

dle

.ser

ialization

.of.the.

fun

ction

.cal

.an

.th

.pa

rameters

.to.SO

.me

ssages

.an

.vi

.ve

rsa.

.the.aut

omation

.dom

ain,

.Web.ser

vices

.are.inc

reasingly

.use

. e.mos

.imp

ortant

.pro

blem

.is.

not.the.too

.sup

port,

.but.the.com

mon

.de

nition

.of.ser

vices.

. is.lea

.to.the.typ

ical

.sta

ndardiza-

tion

.top

ics,

.whi

.are.alw

ays

.har

.to.sol

ve.

.How

ever,

.the.suc

cess

.of.OPC.ena

bled

.a.de

nition

.of.Web.

ser

vices

.to.acc

ess

.exi

sting

.OPC.ser

vers

.for.rea

ding

.and.wri

ting

.of.OPC.ite

ms.

. is.sol

ution

.is.kno

as.OPC

&XML

.[OP

Cxml]

.and.dem

onstrates

.the.pot

ential

.of.Int

ernet

.tec

hnologies.

.Usi

.Web.ser

vices

.red

uces

.the.com

plex

.eo

rts

.of.pro

viding

.the.app

ropriate

.DCO

.con

guration

.dra

matically,

whi

.was.nec

essary

.for.tra

ditional

.OPC.ser

vers.

. e.acc

ess

.can.now.eas

ily

.pas

.re

walls;

.the.ser

vice

ana

lysis

.at.the.ser

ver

.sti

.pro

vides

.sec

urity

.fea

tures.

.Act

ual

.dev

elopments

.lik

.OPC

-UA

.(se

.Cha

pter

56).als

.use.Web.ser

vices.

.How

ever,

.a.dra

wback

.is.int

roduced

.by.the.eno

rmous

.ove

rhead

.of.SOA

mes

sages

.to.be.exc

hanged.

.So.for.OPC

-UA,

.a.spe

cic

.bin

ary

.pro

tocol

.has.bee

.dev

eloped

.to.red

uce

com

munication

.eo

rt.

FIGURE 56.9 Screenshot.of.a.browser-based.visualization.using.SVG.

56-12 Industrial Communication Systems

56.5 Conclusions and Outlook

Internet.technologies.and.applications.have. become. an.integral.part. of.everyday.life.. e.overall.

acce

ptance

.is.one.of.the.driv

ing

.forc

.for.the.adopt

ion

.of.such.tech

nologies

.in.the.autom

ation

.doma

in.

Appl

ication

.scen

arios

.for.this.“Ind

ustrial

.Inte

rnet”

.are.mani

fold

.and.span.the.comp

lete

.rang

.of.task

in.vert

ical

.inte

gration

.of.autom

ation

.syst

ems,

.as.well.as.alon

.the.life.cycl

.Howe

ver,

.the.appr

opriate

tech

nologies

.nee

.to.be.sel

ected

.and.ado

pted;

.the

.can

not

.alw

ays

.simp

.be.use

.stat

.abov

.a.comm

.solu

tion

.for.sele

cting

.the.righ

.tech

nology

.or.tech

nology

.combi

nation

is.not.possi

ble.

.A.syst

ematic

.appr

oach,

.howe

ver,

.is.possi

ble—using

.an.eval

uation

.of.feat

ures

.agai

nst

.a.

list.of.use-

case

.depe

nding

.cons

traints.

. is.appr

oach

.take

.into.acco

unt

.the.func

tions

.to.perf

orm,

.thei

impl

ementation—the

.devi

ces

.and.syst

.comp

onents—and

.the.comm

unication

.aspe

cts

.depe

nding

.on.

the.com

ponents’

.loc

ations.

Besides

.the.tech

nical

.feat

ures,

.the.TCO.need

.to.be.cons

idered.

.Not.only.are.the.inst

allation

.cost

rele

vant,

. but. also.main

tenance

. cost

.and. eor

.for.acqu

iring

. the. appr

opriate

. know

-how.

. Anot

her

impo

rtant

.aspe

.is.the.matu

rity

.of.the.tech

nologies,

.since.the.shor

.tech

nology

.deve

lopment

.cycl

.are.

in.con

trast

.to.lif

.cyc

.dur

ations

.in.ind

ustrial

.auto

mation.

Application

.doma

in-related

.adop

tion

.of.Inte

rnet

.techn

ologies

.lead

.to.stan

dardization.

. is.is.prob

lem-

atic,

.sinc

.the.inu

ence

.of.auto

mation-related

.stan

dardization

.bodi

.like.ISO.or.IEC.is.rath

.limi

ted

.in.

Inte

rnet

.stan

dardization.

.Comp

ared

.with.the.IT.doma

in,

.indu

strial

.appl

ication

.is.a.smal

.doma

in.

.is.obvi

ous

.that.the.actu

.deve

lopments

.of.Inte

rnet

.and.Web.tech

nologies,

.for.exam

ple,

.Web.2.0,.

will.nd.the

.app

lications

.in.the.ind

ustry

.dom

ain,

.ext

ending

.the.rol

.of.Ind

ustrial

.Int

ernet.

acronyms

AJAX. Asynchronous.Javascript.and.XML

ASP

. Acti

.Ser

ver

.Pag

CGI

. Comm

.Gat

eway

.Int

erface

CORBA

. Comm

.Obje

.Req

uest

.Bro

ker

.Arc

hitectures

CSS

. Casc

ading

.Styl

.She

ets

DCOM

. Dist

ributed

.Com

ponent

.Obje

.Mod

DOM

. Docu

ment

.Obje

.Mod

DTD

. Docu

ment

.Typ

.De

nition

EDD

. Elec

tronic

.Dev

ice

.Des

cription

EDS

. Elec

tronic

.Dat

.She

ERP

. Ente

rprise

.Res

ource

.Pla

nning

FDCML

. Fiel

.Dev

ice

.Con

guration

.Mar

kup

.Lan

guage

FTP

. File.Tra

nsfer

.Pro

tocol

GSDML

. Gene

ric

.Stat

ion

.Des

cription

.Mar

kup

.Lan

guage

HTML

. Hype

rText

.Mar

kup

.Lan

guage

HTTP

. Hype

.Tex

.Tra

nsfer

.Pro

tocol

HTTPS

. HTTP

-Secure

IMAP

. Inte

rnet

.Mes

sage

.Acc

ess

.Pro

tocol

. Inte

rnet

.Pro

tocol

JVM

. Java.Virtual.Machine

MES

. Manu

facturing

.Exe

cution

.Sys

tems

MIB

. Mana

gement

.Inf

ormation

.Bas

NNTP

. Netw

ork

.New

.Tra

nsfer

.Pro

tocol

OPC

. OLE.for.Pro

cess

.Con

trol

OPC-UA

. OPC.Uni

ed

.Arc

hitecture

POP

. Post.Oc

.Pro

tocol

Industrial Internet 56-13

SAP. Service.Access.Point

SMTP

. Sim

ple

.Ma

.Tr

ansfer

.Pr

otocol

SNMP

. Sim

ple

.Ne

twork

.Ma

nagement

.Pr

otocol

SoA

. Ser

vice-oriented

.ar

chitecture

SOAP

. Sim

ple

.Ob

ject

.Ac

cess

.Pr

otocol

SVG

. Sca

lable

.Ve

ctor

.Gr

aphics

TCO

. Tot

.co

.of.ow

nership

TCP

. Tra

nsmission

.Co

ntrol

.Pr

otocol

UDP

. Use

.Da

tagram

.Pr

otocol

WSDL

. Web.Se

rvice

.De

scription

.La

nguage

XML

. eXte

nded

.Ma

rkup

.La

nguage

XSD

. XML.Sc

hema

.De

nition

.La

nguage

XSLT

. eXte

nsible

.Sty

.La

nguage

.fo

.Tr

ansformation

references

[CORBA]. e.Common.Object.Request.Broker:.Architecture.and.Specication,.Object.Management.

Gro

up,

.p://

p.omg.org/pub/docs/

[CSS98]

.RFC2318:. e.text/css.Medi

.Type

.Int

ernet

.Engin

eering

.Tas

.For

.(IETF),.1998,.htt

p://tools.

ietf.org/html/rfc2318

[DBX00]

.D..Box.et.al.,.SOAP:

Simple Object Access Protocol.

.Micros

o

.Cor

p.,

.2000..htt

p://msdn.microso.

com/xml/general/soapspec.asp

[DOM98]

.Doc

ument

.Obj

ect

.Mode

.(DOM).Lev

.1.Spe

cication,

.Versio

.1.0,.W3C.Reco

mmendation,

Oct

ober

.1,.1998,.ht

tp://www.w3.org/TR/REC-DOM-Level-1

[EDS00]

.W.H..Moss,.Repo

.on.ISO.TC184/SC5/WG5.Open.Syst

ems

.App

lication

.Fram

eworks

.bas

.on.

ISO.11898,.In:.Pro

ceedings

.“In

dustrial Automation”

.of 5t

h International CAN Conference (iCC’98),

San.Jos

.CA,.No

vember

.3–5,.1998,.pp

.07-02–07-04.

BO98]

.F..Bou

mphrey,

.Pro

fessional

.Sty

.She

ets

.for.HTM

.and.XML

.Wro

.Pre

ss,

.Bir

mingham,

.U.K

.199

[FDC01]

.Field.Dev

ice

.Congura

tion

.Mar

kup

.Lan

guage.

.FDCML.2.0.Spe

cication,

.htt

p://www.fdcml.org

[FTP85]

.STD.9:.File.Tran

sfer

.Pro

tocol,

.RFC.959,.Int

ernet

.Engin

eering

.Tas

.For

.(IETF),.1985,.htt

p://

www.apps.ietf.org/rfc/rfc959.html

[GSD06]

. GSDML. Spe

cication

. for. PRO

FINET

. IO,. PRO

FIBUS

. Nutzer

organisation

. e.V,. Versio

. 2.1,.

Augus

.2006.

TM00]

.ISO

/IEC

.154

45:2000-Information

.tec

hnology—Document

.des

cription

.and.pro

cessing

.lan

guages—

HyperText

.Mar

kup

.Lan

guage

.(HT

ML),

.Int

ernational

.Org

anization

.for.Sta

ndardization,

.200

.htt

ps://

www.cs.tcd.ie/15445/15445.HTML

[HTTP99]

.RFC2616:.Hyper

text

.Tran

sfer

.Pro

tocol—HTTP/1.1,

.Int

ernet

.Engin

eering

.Tas

.For

.(IETF),.

1999,.ht

tp://tools.ietf.org/html/rfc2616

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