IDL-XML based information sharing model for enterprise integration

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IDL-XML based information sharing model for

enterprise integration

Uanny Brens Garcia

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Recommended Citation

IDL-XML Based Information Sharing Model for

Enterprise Integration

Uanny M. Brens Garcia

B.S. Pontificia Universidad Catolica Madre y Maestra

(Santiago, Dominican Republic 1998)

Thesis

submitted

in

partial

fulfillment

of

the

requirements for the degree of Master of Science in the

Department

of

Industrial

and

Manufacturing

Engineering in the Kate Gleason College of Engineering

of the Rochester Institute of Technology

KATE GLEASON COLLEGE OF ENGINEERING

ROCHESTER INSTITUTE OF TECHNOLOGY

ROCHESTER, NEW YORK

CERTIFICATE OF APPROVAL

MASTER OF SCIENCE DEGREE THESIS

The M. S. Degree Thesis of Uanny M. Brens Garcia

has been examined and approved by the thesis committee

as satisfactory for the thesis requirement for the

Master of Science degree.

Sudhakar Paidy, Ph.D.

Advisor

Permission granted

IDL-XML Based Information Sharing Model for Enterprise Integration

I, Vanny M. Brens Garcia, hereby grant permission to the Wallace Library of the Rochester

Institute of Technology to reproduce my thesis in whole or in part. Any reproduction will not be

for commercialllse or profit.

Dedication

To theBrens

family

andtheGarcia Family.

They

havetaught me

Acknowledgment

Throughout the time I _{have been working in} this research study,

many people have assisted me. It is impossible to acknowledge them all, nevertheless, I would like to _specifically thank the

following

individuals:

Dr. Sudhakar

Paidy,

for all the time he dedicatedto _myresearch workandfortheknowledge he has shared withmeinthelasttwo years. This thesis would not have been possible without your

help.

Dr. Wayne

Walter,

for his support and comments on _my work. I

hopeyouenjoyed

being

amember of_mythesiscommittee.

The

faculty

and staff of the Industrial and

Manufacturing

Engineering

Department,

not_{only for}theiracademic supportand

feedbackon _my work, but forall the advise given throughout_my careeratRTF

Dr. James

Miller,

Dr. Jasper

Shealy

and the officials at PUCMM

for setting up the program that allowed me to pursue thesis MasterofScience Degree.

To

Anne, Kevin,

Kaine,

Sri, Judith, Seau, Tara, Jenny,

Joy

and

Tom for

helping

me from the

beginning

of the

thesis,

proofreading, giving me feedback and support. But mostly, for

Outline

Section

Page

1.

Abstract

9

2. Introduction 10

3. Computer Integrated

Manufacturing

14

3.1. Description andBackground 1 4

3.2. CIM Architecture: The National Institute of Standards and 14

Technology

CBVI ArchitectureModel 3.3

.ManufacturingExecution SystemsAssociation 1 9

3.3.1. InformationSystem Architecture 1 9

3.3.2. Enterprise Resource

Planning

22

3.3.3.

Manufacturing

Execution Systems 24

3.3.4. Control Systems 29

3.4.

CORBA,

STEP,

DCOMandInformation

Sharing

30

3.4. 1 CORBA Definition 3 1

3.4. 1.2

Manufacturing

Execution SystemsandCORBA 32

3.4.2 XMLDefinition 33

3.4.2.1 XMLandEnterprise Communication 35

4. Relation between Information SystemsandEnterprise Wide Data 36 4.1 Relation between Information SystemsandEnterprise Wide Data 36

4.2 Information Systems andPurchaseInformation (Customer/Supplier 47

perspective)

5. Common ObjectRequestBroker Architecture 50

5.1 Distributed

Computing

andSoftware Architecture 50

5.2 CORBA

50

5.2.1 CORBA Components 52

5.3 Object Request Broker 54

5.3.1 DefinitionandHowit Works ₅₄

5.3.2InteroperableObject Request Broker

56

5.3.3 Fault

Tolerance,

Object Migrationand

Garbage Collection

57

Section

5.3.5 Remote Procedure Callsvs.

Object

Request Broker

5.4

Interface

Definition Language

5.5

Object

Management Architecture

5.5.1 CORBA

Services

5.5.2 CORBA Facilities

5.5.3 Application Objects

5.6 CORBA's New Features

5.7 BenefitsofCORBA

Page

61

62

63

64 65

66

66

68

6. Extensible

Markup

Language

6.1 Standard Generalized

Markup

Language 6.1.1 Document Type Definition

6.1.1 Elements 6.1.2 Attributes 6.1.3 Entities

6.2extensible

Markup

Language

6.2.1 Document Type Definition in XML

6.2.2 Application

Processing

Interfaces for XML 6.2.3 Extensible Style Sheets

6.2.4 XML Applications

6.3 XML Three Tier Architecture

7. JDL-_{XML Architecture for Enterprise Integration}

8. References

9. Appendix

70 70 72 73 74 74

76 79 80 81 81

82

84

91

Tables

and

Figures

Table Number

3.1 3.2 3.3 3.4 3.5 3.6

Name

of

Table/Figure

Page

The NBS Model for

Manufacturing

Plants 18

MESA Context Model 20

Relationship

between MESAarchitecture andCTMArchitecture 21 FlowofInformation(Between

ERP,

MES and

Controls)

24

MEStoControls data flowpossibilities 25

MES Functions 28

4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11

Information SystemsandenterpriseData Tables MasterSchedule

Materials Requirements

Planning

Capacity

Requirements

Planning

Resource Acquisitions and

Purchasing

Inventory

Management

Product/Engineering

Data Process ControlSystems

Human Resources Management

Accounting

andFinance

SupplierPerspectiveofInformation Customer PerspectiveofInformation

38 39 40 41 42 43 44 45 46 48 49 5.1 5.2 5.3 5.4 5.5

CORBA Busmodel

Structureof aCORBA ORB

Remote ProcedureCallsvs. Object Request Broker

CORBA JLD Language Bindings The Object Management Architecture

51 52 61 62 63 6.1 6.2 6.3 6.4

XMLCode Example

XML's Tree Structure

Document Type Definition for

Inventory

.xml Three-Tier Architecture 78 79 80 82 7.1 7.2 7.3

IDL-XMLArchitecture for Enterprise Integration

Interactionofthefour layersofTXA

Information

Sharing

Situationswith theIXA Model

85

87

88

APPENDIX

MICOApplication. Examples if CORBA DDLcode

SGML document: Transcription andTagged Versionof aletter HTML document: Webpage

display,

and HTML

file

1. Abstract

CJM is a mechanized approach to problem _solving in an enterprise. Its basis is

intercommunication

between information systems, in order to provide faster and more effective

decision makingprocess.These results

help

minimizehumanerror, improveoverall_productivity

and guarantee customersatisfaction.

Most enterprises or corporations started

implementing

integration

by

_adopting automated

solutionsinaparticular_process,

department,

orarea,in isolation from therest ofthe physical or

intelligent process _{resulting in} the

incapability

for systems and equipment to share information

witheach other andwith other computer systems.The goal ina_{manufacturing}environmentis to

havea setof systems that will _{interact seamlessly}with eachother within aheterogeneous object

framework overcomingthe_{many barriers}

(language,

_platforms, andeven physical

location)

that

donot grantinformationsharing.

This study identifiesthedataneeds of severalinformation systems of acorporation andproposes a conceptual model to improve the _{information sharing} process and thus Computer Integrated Manufacturing.

The architecture proposed in this workprovides a _{methodology for datastorage,} data retrieval,

anddata processing inordertoprovideintegrationattheenterpriselevel. There are four layersof

interaction in the proposed IXA architecture. The name TXA (DDL

-XML Architecture for Enterprise

Integration)

is derived fromthe standards and technologies used to define the layers

and_{corresponding functions}of eachlayer. The first layeraddressesthesystems andapplications

responsiblefor datamanipulation. Thesecondlayerprovides theinterface definitionstofacilitate

theinteractionbetweenthe applications onthefirst layer. The thirdlayer is where datawouldbe

structured _{using XML} to be stored and the fourth layer is a central _repository and its database

2.

Introduction:

Since

their

introduction,

computers(andcomputer-assisted applications) have been developed to

better

serve

humans.

They

_{have been widely} used throughout _{manufacturing} environments. In

1953,

General Electric was one of the first organizations to use computers in financial applications. One year

later,

numerical controlmachines were

introduced;

and then in

1955,

the

first

automatically

programmed tool started what we now know as Computer-Aided

Manufacturing

- CAM

(Shrensker,

1991).

Afterthe

1950's,

computers havebecome

faster,

smaller andmore affordable.Thisresultedin numerous computer applicationsfor different manufacturingtasks.Computer Aided Designwas made publicinthe_{early 1960's}andotherCAMsoftwarelike Materials Requirement

Planning

(MRP)

hadtheirfirstappearanceinthe_{early 1970's}

(Robinson,

2000). MRPisa software developedto

help

with_{scheduling tasks, but it has}turnedoutto_{have relatively}poor

performance

(Robinson,

2000). Thenext generation ofComputer Integrated

Manufacturing

(CIM)

was

Manufacturing

Resource

Planning,

orMRPIJ. Itwas withthese twoapplications

(MRP,

and

MRPIT)

that the termComputer Integrated

Manufacturing

was coined. Dr. Joseph Harrington firstusedthe termin

1974,

but itwas not until 1981 that_{it became widelyused,} probablyafterMRPandMRPIJbecamepopular

(Shrensker,

1991).

Since

1981,

computershave evolvedfrom

having

acouple ofhundredsofkilobytes of_memory to several gigabytes of _memory

(among

other resource enhancements), making them _very powerful and _{enabling many}computer-aided systems to be developed. For_example, computer-aided engineering, computer-aided systems for _{manufacturing} process _{planning, shop}

scheduling,

inventory

control, decision support, human resources _{applications,} and diverse financial applications were _making common appearances in 1980s within _{manufacturing}

environments

(Shrensker,

1991).

Today,

applications are run not_onlyondedicated systems,but arerun across multiple computers andacrossnetworks.

They

areas complexasmainframes oras

smallas sensors andlogic controllers;and the_{manufacturing floor includes}varied computerized devices such as robots and robotic cells, computer numerical controlled _machines, automated decisionsupport_systems,etc.

Computer Integrated

Manufacturing

comprises not _only the product _making activities such as engineering and _{manufacturing but} all the disciplines within an enterprise

including

_marketing, sales,

distribution, finance,

human resources, and general office administrations.

According

to Shrensker: "A

fully

integrated CEVI system involvesthe

design,

development,

or application of

each of the systems in such a manner that the output of one system serves as the

input

of another"

(Shrensker,

1991). Inother_words, Computer Integrated

Manufacturing

isan

enterprise-wide effort, where the data would

"flow"

from one place to another and

improve

the

business

process.

The

Society

of

Manufacturing

Engineers defines

CIM

as the

integration

of the total

manufacturing enterprise through the use of

integrated

systems and

data

communications

coupled with new managerial philosophiesthat

improve

organizational and personnel

efficiency

1980's

the general concept ofComputer Aided

Manufacturing

leadto what is known as

Islands

of

Automation. Computer

Integrated

Manufacturing's

aim was to integrate these

independent

systems

(Vernadat,

1996). Bartlett explains that CIM

is

concerned with _providing computer assistance and _{control, along} with

high-level

integrated

automation at all levels of the

manufacturing

industries,

by linking

islands

of automation into a distributed processing system

(Bartlett,

1995).

Many

companies in the United States and most companies in

developing

countries still handle theoutput of automated systems withmanual techniques.Thereremains a _{gap between} whenthe

information is needed and when itcan be delivered (this is based on the time it takes to collect

the data manually). The solution should be a _{responsive, adaptable,} and reliable computer systemsthatsupportstheCIMconceptthroughout theenterprise

(Attran,

1995).

The basisofComputer Integrated

Manufacturing

is intercommunication betweentheinformation systems processorstofacilitateafasterand moreefficientdecision makingprocess. Processorsat all decision makingand_{supervisory levels}of anenterprise needthe_abilityto gatherthe dataand

track the status of operations _necessary to assess _{manufacturing efficiency}

(Snyder,

1997). Specialized software, plustheintegration ofdatasystems, providesthe typical firmwith a much

morerobust systemthanhas beenpossible inthepast

(Oleson,

1999).

The problem facedwith CIM is nicely described

by

Bubsy,

when heexplains that the principal

computer applications in a_{manufacturing company} are large and _{substantially isolated} systems bought from differentsuppliers and_originallyspecifiedtobe

freestanding

ofothersystems.

They

run on different types of_machines, use _{different operating systems,} and

they

are _{generally built} ondifferent databasemanagementsystems

(Bubsy,

1992).

But

Bubsy

is notthe_onlyauthorconcerned withthepoorintegrationof systemsin an enterprise.

Associations such as the

Society

of

Manufacturing

Engineers

(SME),

the

Manufacturing

Executions Systems Association (MESA

International),

and companies like

Boeing

devote their time to research thecurrent

technology

andto

develop

new

technology

that would improve the

integration intheenterprise.

Many

researches havealso expressedthe need forapplications and

information systems to have seamless communication in order to achieve full enterprise integration

(Allegri, 1989; Hardwick,

1996;

McClellan, 1997; Adelsberger, 1995;

Scharpf, 1999;

Singh, 1996;

and

Svenson,

1993).

The importance of information and data sharing through the _{manufacturing}

facility

lies

in the

fact that accurate and consistent information is crucial to make

business decisions

and process

improvement

(Bhatt,

2000). Since the last quarter of the Twentieth

Century,

automation has forced _{manufacturing} companies to

develop

more and more sophisticated computer communication strategies in ordertoguarantee theirmaximumbenefit to the

company

(Bartlett,

1995). The _availability of better

data,

advances in analytical

techniques,

and ever

improving

communications enhance a company's _ability to make more complex and effective

decisions,

andthusmaintains acompany'scompetitiveedge

(Metz,

1998).

Information

is

not_only neededinan accuratemanner,

it is

also neededin a

timely

fashion.

Real

real-time, accurate, reliable,

flexible,

and modifiable to interface

directly

with the

departments

that

have

the

responsibility

of _{controlling the processes,} and in predicting the results of their

actions and

decisions

(Rathmill,

1998). Information

Systems

(IS)

and Information

Technology

solutions, throughcommunication networks and

database

_systems, enableorganizationstocreate and sustain process improvement

(Bhatt,

2000). The tools exist to

develop

technologies and to

acquire

integration

throughout the enterprise.

Today,

most information systems and systems

integration

vendors work toward the

development

of an enterprise-wide system that contains a central

database

compiled from the operations of multiple machines and multiple processes

(Snyder,

1997).

Companies

like Adasoft

Group

_saythata

factory

mustbe consideredas a_whole,

where the systems for administration, management, maintenance _control, follow _up and command cannotbe independent (Adasoft

Group,

2000).

In order_{for manufacturing} applications to communicate _efficiently, an information structure is needed. Although the nature ofthe _{information is diverse in manufacturing} environments, this

information is

frequently

commontootherapplications

(Busby, 1992; Hardwick,

1996). Thereis

theneed of structured_{information sharing}methods and models thatwould allow datatobeused

by

the different applications and systems.

Bubsy

makes the point that if no mechanisms are introduced to _specifically regulate the information _sharing process, there is a risk of

inconsistency,

duplicationand omission ofdata

(Bubsy,

1992).

The Computer Integrated

Manufacturing

Architecture (CIM

Architecture)

explainedin

following

sections gives aschemaofhow information flows in a_{manufacturing}environment. In the same

way, the

Manufacturing

Execution Systems Association's Context Model (MESA Context

Model)

defines the six information systems relevant to an enterprise and relates these systems according to the data shared. These two architectures share _many of the basic concepts of

information flowand we present adiagramthatrelatesthese twoarchitectures.

Furthermore,

the _{relationship between}the dataof an enterprise and the six information systems

(Enterprise Resource

Planning,

Supply

Chain

Management,

Sales and Service

Management,

ProductandProcess

Engineering,

Manufacturing

Execution Systems and

Controls)

_{is graphically}

shown in tables. These tables have the objective of _reinforcing the concept that

information

is

commontodifferentdepartments and systemsof an enterprise.

Thus,

agoodinformation

sharing

architectureshouldbe implementedtoimprovethe_{data sharing}process.

The objective of this thesis work is to propose an architecture thatprovides a

methodology

of data storage, dataretrieval, and _{data processing in} order to provide

integration

at the enterprise level. The modeldeveloped itscalledIDL-XML

Architecture

for Enterprise

Integration

(IXA for Enterprise Integration). There are four layers of interaction in the proposed TXA architecture.

The name IXA Enterprise Integration is derived from the standards and technologies used to

definethe layersand_{corresponding}

functions

ofeachlayer.

The two technologies used to

develop

the IXA are the

Common

Object

Request Broker

Architecture

(CORBA),

and the extensible

Markup

Language (XML).

CORBA is

a set of

standards that establishes the

interfaces

and parameters

for

applications to

interact

with one another. One of

CORBA'

The

XML

is a

markup

language thatdefines how datawouldbe structure; itgives thecontrol of

how

thedatawouldbe displayedand manipulatedto theapplication_usingthe data.

Therefore,

CORBA and XML are the basis of the

IDL-XML

Architecture for Enterprise

Integration

proposedinthiswork. Thepurpose oftheIXA modelis tofacilitatethe information

storage, retrieval, and _processing of information across the enterprise. Since data are collected and utilized from systems of different _platforms,

languages,

_{applications, allocations,} etc., it

makes the process of information access, utilization, and _{sharing difficult.}

By

_using a central

repository, or common databasestorage,therewouldbe aplace forallhardwareand/orsoftware inthecorporationtostore andretrieveinformationwhenneeded. Interaction betweenthe central

repository and the information system would be controlled and manipulated

by

layers of

software that would act as an intermediate access manager, and would restrict the information sharing and access process. The concept is to

develop

interface layers (based on CORBA and

XML)

betweenthesystems andthecentral repository.

The IXA model would provide the means for communication _{among information} systems via

CORBA. It structures the _{data using XML}

hierarchy

to allow a better navigation through

digitally

represented documents and

information,

and provides an API interface

(using

CORBA'

3.

Computer

Integrated

Manufacturing

3.1

Description

andBackground

Computer Integrated

Manufacturing

is a modern

manufacturing

paradigm. Itaims at integration

of man and machine activities

by

facilitating

_{communication,} cooperation and coordination of

thevarious

technical,

_{administrative,} and support

functions

ofa_{manufacturing}company. It aims

to achieve this

by

means of information and communication technologies, from design to

production _planning, from control to _{manufacturing} and _shipping

(Vernadat,

1996). The

importance

of data communications is further emphasized

by

the

Society

of

Manufacturing

Engineers;

SME states that data communication

improves

organizational and personnel

efficiency inacorporation.

Usually,

solutionsdevelopedtoimprove an areainvolveasingleautomationtool.This conceptis known as "IslandsofAutomation" and itwas themost _prevailing model ofcomputerintegrated

manufacturing in the 1980's. As a result of _this, automated solutions are implemented in a particular _process, department or area, in isolation from the rest ofthe physical or intelligent

process.

However,

the

key

is to approach enterprise's problems with an integrated set oftools

that will consider and fix all the problems at once and improve over all production

(Vernadat,

1996). Thisiswhatis knownasComputer Integrated

Manufacturing

(CIM).

Computer Integrated

Manufacturing (CIM)

became thesolutionforanintegratedset of problems recognized

by

companies. The

Society

of

Manufacturing

Engineers

(SME)

defines CIM as the

interaction ofthe total _{manufacturing}enterprise through theuse ofintegrated systems and data

communications coupled with new managerial philosophies that improve organizational and personnel _efficiency

(Rehg,

1994). Inother_words, Computer Integrated Manufacturing'sgoal is

to integrate man and machine activities

by facilitating

_{communication,} cooperation and

coordination ofthe various _technical, administrative and support functions of a _{manufacturing}

company,

by

means ofinformation and communication technologies between

design,

_planning,

control and _shipping (Vernadad. 1996).

Thus,

Computer Integrated

Manufacturing

is a

mechanized approach to problem _{solving in} an enterprise. Its basis is

intercommunication

between information systemsto providefaster and more effective_{decision making process,} and

as a result minimizes human error, improves overall _productivity and guarantees customer satisfaction.

3.2 CIMArchitecture

Information flow in an enterprise is crucial to determine the design and

implementation

_{of an}

integration system.

By

_referring to the National Institute of Standard and

Technology

(NIST)

model for manufacturing plants, we notice the

hierarchy

of the

different

activities within a

company. If we follow this model to structure the

information

flow,

so that each

layer

communicates _only with the layer

directly

above or

directly

below,

the

sharing

and

flow

ofthe

The

NIST developed

the

Shop

Floor Production Model

(SFPM)

as ageneric architecture

for

real

time production control. It is based on a tree-shaped

hierarchy

with command/feedback control

structure, where the control processes are

isolated

by

function

and communicate via standard

interfaces (Jones

et _al, 1986). This approach ensures that the size,

functionality

and _complexity of

individual

_{control modules are limited. Each} of the modules in this architecture has to be

designed

in a _way that humans can comprehend and interact with them.

Also,

hierarchical

approach reducesthe _complexityofthecontrol problems because thecontrol resides at the next higher level and the decisions are made at the lowest possible level

(Jones, 1986;

RathmiH,

1988).

Every

control module decomposes its current

input

command from its supervisor into

procedures to be executed at that

level,

subcommands to be issued to one or more lower modules, andstatusfeedbacksentbackto thehigher level

(Jones,

1986).

The SFPM

hierarchy

has been developed basedoncontrol_modules,each of whichis determined

by

its planning horizon. The planing horizon is the period of time over which the module is

responsiblefor planingand_{updating local}goals. Themainprinciplebehind SFMParchitecture is

that _{processing becomes} more and more time critical at the lower levels ofthe

hierarchy;

thus,

the_{planing horizon becomes} smaller atthe lower levels and the _{processing becomes} more time critical.

(Rathmill,

1988).

Thedifferent levels oftheNIST CEVIS architecture are:

Level 5

-Facility

Control System (Alsocalled:Plant

level,

Enterprise

Level,

Factory

Level):

This is thehighest levelof control andits implemented in thefront office._{The planning horizon}

can be anywhere from several months to years. _{Its responsibility is for} overall _planing and

execution; itmanagestheproduction offinishedproducts

by

_{controlling job} shops. Its decisions

are strategic innature,and ofgreatimportance forthecorporation. This levelgives support to the CIM system through the integration of orders, sales

data,

_{manufacturing, shipment,} and

invoicing.

Factory

level is broken down insubsystemsthatfall intothreemajorfunctional areas:

Manufacturing

engineering:Herearethefunctions

typically

carriedoutwithhuman

involvement

via userdata interfaces (i.e. CAD/CAM).

Information management: Provides user data interfaces to support _necessary administrative or

businessmanagement functions (i.e. cost _estimation,job cost _accounting,

inventory

_accounting,

etc).

Level 4

-Shop

Control System

(Alsocalled

Factory level)

The

shop

control system manages the production of parts and part's component

by

_controlling

work centers. Itcoordinates theproduction and support activitiesthat are carriedout

by

the cell controllers at the nextlower level. This level

is

responsible _{for coordinating} the production and support

jobs

onthe

shop

floor,

andit

is

also responsible forallocationofresourcesto thosejobs.

However,

the main function of this level is to schedule production and provide management

information

by

_monitoring and_supervisingthelower levels ofcontrol.

The

decisions

ofthe _shopcontrol system areboth strategic and operational, andit has a_planing

horizonthatcouldbeanywherefromseveral weeks toseveral months.

Twomajor components ofthislevelare:

Taskmanager: Schedules job orders, equipment _maintenance, and _shop support _services; it also

tracksequipmentutilization, schedules preventive _maintenance, andmaterial transferequipment

inthefactory.

Resource Management: It allocates workstations, buffer storage areas, trays, tooling, and

materialstocelllevelcontrol systems forparticular productionjobs. Italso monitorsand updates

levels for all raw _stock, work in _{process, cutting tools,} and replacement parts inventories

necessarytorunthefactory.

Level 3- Cell Control System (Also_called: Area

Level,

_andCell Level):

Cell control system's _{responsibility} is the _sequencing of batch jobs of similar parts though

workstations and _supervising other support _services, for example material

handling,

or calibration. This level is in charge oftasks like goods storage and retrieval, and transportation

and_{manufacturing}of parts. Itdirectsand coordinatesthe_{shop floor}production_process,butalso,

coordinates production flow among various stations and integrates individual stations into an automated system. Modules within the work cell level perform task

decomposition,

analyze resource requirements, prepare requisitions, report job progress and system status to the _shop

control _system, makedynamic _{batch routing}

decisions,

and schedule operations. Also it

decodes

the order received from the higher level into more _elementary

manufacturing

jobs so that

machinecells can process theinformation.

The planning horizoncan be anywhere from several hoursto several _weeks, andthe

decisions

it takesareoperational innature.

Level 2 - Workstation Control System (Alsocalled:

Work-center

Level,

orStation

Level):

Workstation level coordinatesanddirectsthe activities of_small,

integrated

physical groupingsof

This level

is in charge of_converting the

input from

lower

levels

to output commands, since it

exchanges

data

with_{the scheduling,} production

planning

andmaterial

handling

activities and at thesametimewiththecontrollers, actuators, and sensorsfromthe lower levels.

At the

Workstation

Control System the _{planning horizon} can be anywhere between several

minutestoseveral

hours,

andthenatureofthedecisions

is

operational.

Level 1-

Equipment

Control System (Also

called Machine

level,

orEquipment level):

Here is where basic interface with plant floor equipment takes place. The main tasks of the Equipment Control System areto translate thecommands fromthe workstation controllerinto a

sequence of simpletasksthatcanbeunderstood

by

thevendor supplied controllerandto monitor theexecutionofthose tasksviathevarious sensors attachedto thehardware.

The equipment control system acts as the interface between the workstation control system

above and the vendor supplied controller on the hardware under its control.

Therefore,

the informationgathered comes fromtheexecution ofthejobatthe_{shop floor. The planning horizon}

may beanywherebetweenseveral millisecondstoseveralminutes.

Level0- Floor level:

This level is comprised of all the devices that perform direct action on the _{manufacturing}

process,i.e. sensors,and actuators. Theirtaskistocollectinformationrelated to theexecutionof the job at the _shop

floor,

and to _carry out the commands in order to

keep

the _{manufacturing}

process running.

They

have the smallest _{planning horizon} and _{fastest processing} and decision

Level5

FacilityLevel

Manufacturing

Plant

Level 4

Shop

Level

Machine

Shop

Assembly

Shop

Level 3

Cell Level Virtual

Celll

Virtual

Celln

Level 2

Work Station Level

Milling

WorkStation

Inspection

Work Station

WorkStation

n

Level 1

Equipment Level

Robot

Milling

Machine

Robot Inspection

Machine

Robot Part

Buffer

Level0

FloorLevel

Sensors &

Actuators

Sensors &

Actuators

Sensors &

Actuators

Sensors &

Actuators

Sensors &

Actuators

Sensors &

[image:19.553.26.516.147.509.2]

Actuators

3.3

Manufacturing

Execution

Systems Association

3.3.1 MESA Information

Systems

Architecture:

The

Manufacturing

Execution Systems Association International (MESA

International)

has

developed

an

Enterprise

Information System

Architecture

orContext Model. This model

depicts

the relation

between

the major _{manufacturing} software systems categories. Each system

(Enterprise

Resource

Planning,

Manufacturing

Execution

System,

Supply

Chain

Management,

Sales and Service

Management,

Product andProcess

Engineering,

and

Controls)

is the _grouping

of different applications and functions of an enterprise.

Thus,

an enterprise needs some

functionality

from each ofthese systems in order to achieve success (MESA 1997). The scope and utilizationofthesystems willdepend onthetype ofenterprise and _{manufacturing}process it has (if it is a service_provider, adiscrete manufacturing,continuous,

batch,

or _{assembly process,}

make_{to order,}etc).

MESAgivesthe

following

definitions foreachsystem:

Enterprise Resource

Planning

(ERP): Consists ofthose systems that provide

financial,

order

management, production, and material planning. ERP is a _{manufacturing information} system

whose focusgoesbeyond

inventory

control anddistributedmanagement activities. Its purposeis to

bring

together areas like engineering,

finance,

human resources, project _management, etc.

Moreover,

it can be consider as a medium to achieve the connection via computer _systems, between the different subsets of _{manufacturing} systems. ERP is more concerned about

automationand computer-aidedprocessesofthe

integration,

andhence is theinformationsystem thatautomates core activities of an enterprise.

Sales and Service Management (SSM): Comprises software to support the sales _activities, as

well as after sales service. It takes care of sales automation, product _{configurations,} services

quoting, product_return, andso forth.

Supply

Chain Management (SCM): Includes functions as

forecasting,

distribution

and

logistics,

transportation management, e-commerce, and advanced _planning systems.

Supply

chain management is the logical customer-focused progression of physical

distribution

and logistics management, it incorporates the material flow functions of _receiving raw material or

sub assemblies, manufacturing, distribution and

delivering

(Metz,

1999). It

is

a network of facilities and distribution options that performs the functions of procurement of _materials,

transformation ofthese materialsinto intermediateand finished _products, andthe

distribution

of thesefinishedproductstocustomers

(Ganeshan,

2000).

Product and Process

Engineering

(P&PE): Includes computer aided

designs

and

manufacturing, process modeling, and product datamanagement. P&PE

keeps

track ofthe

life

cycle for both the products andthe process. It

is

the tool thatcaptures the

learning

that goes on with the product and process. The system collects data

from

the process and turns it

into

information about the process. It then analyzes the

information

and

determines

what course of

Manufacturing

Execution

Systems

(MES):

The Information Systemthatprovides

information

to

effectively

execute operations in order to meet business goals.

Using

current and accurate

data,

MES guides,

initiates,

responds toand reports on plant activities astheoccur. The resulting

rapid response to change gives as an output effective plant operations and processes. MES

provides mission-criticalinformation about production activities acrosstheenterprise and _supply

chain via

bi-directional

communications

Controls:

Systemsandcomputerizedprocess controls designedtomonitorand adjust the_{way in}

which products are

being

manufactured. Control systems are _necessary to collect and process

information about certain tasks and attributes in order to maintain the _{manufacturing} process

running in accordancetowhat is expected and to makethe appropriate decisions when required

(Vaughn,

1967).

MES

Context

Model

Key; MES

-Martir stujrnsg ixmnakmSystem SSM=_{Sa"ei& Servicehtenaganssrat}

ssm-%ijppt'fChamManagement EBfTsEluapfHaStesourcffl_p!amg

PK-=PrcductandPtceasi_EjigiraerBg ContKite

-ftZ, MStineand imtitim tat&nA

P/PE

\s^.

Controls

/

MESprovidos an snfamationhubthat Sinks loand sometimesbetweenallof thesesystems.MtSoverlapswishother maiusfacturtngsjsIbibIjpes,winchalso

overlapwith eachother.Forexample,

sctxctulitxjmayappearin bahMESami

SCM;tabormanagBmBfflinMES, SSM

aniltheHRfunctionofERi*document controlin-MESandP/Fl;andproems managementin both MESandControls. Degressof_{o'/alap>yby industry}arid

[image:21.553.119.403.365.613.2]

implementation.

After

a close

look

at

both

theMESA Information Context Model andtheNIST CIM Architecture

model, a

similarity

in

functionality

can

be

noted. Each model describes the relation between

systems and applications within a

manufacturing

_environment; both depict similar type of

implementation

intheirrespective model.

The tasks or

functions

of an enterprise are classified _according to _similarity of information

shared, type of resources used, and the significance ofthe output with other functions in the enterprise. The CIMmodelpositions theactivities_{involved in job shop}production

hierarchically

with respect to management _activity and area of _{responsibility}

(Vernadat,

1996). The MESA model relatestheactivities on anenterprise_accordingtotheinformationshared.

Similarities

between

the twomodels confirmtheflowofinformationwithin an _enterprise, where

all aspects of _{manufacturing} and front office functions have to be considered, but where

communication in all directions _among all systems is not possible. This communication

incompatibility

is due tothe different nature ofthe

interacting

functions,

and is the cause ofthe emerging manufacturing integration systems with object oriented functions and distributed computing.

Based on the _similarity of information

flow,

we could _map the MESA system functions to the CIMS architecture. This would giveus an ideaofthe area ofapplication each function on the MESAsystem addresses.

o E a o

ERP

SSM P/PE

SCM

MES

CONTROLS

MESA Architecture

Enterprise level (Level

5)

Arealevel (Level

3)

Factory

level (Level

4)

Cell level (Level

2)

Equipmentlevel (Level

1)

Floor level (Level

0)

[image:22.553.57.438.410.629.2]

CIM

Architecture

The components ofthe Floor and

Equipment level

(sensors,

actuators and _{controllers) monitor,}

regulate and _manipulate,

in

a

direct

_{manner, the manufacturing} operation. The Control

System

would manage these

devices,

and would share the _{necessary information from} the process with

theMES.

The Cell level needs the _scheduling and production

planning

information inorder to handle the

proper

instructions

to the lower levels. The

Shop

Control System

is

where that production

planning

is processed.

Moreover,

MES

is

the "virtual supervisor". It looks over the controllers and actuators to make sure the process _{is running accordingly; it} prepares the _scheduling and

keeps

production records.

While SCM consists of

forecasting,

logistics and advancedplanning; the AreaLevel makes the

sequence of jobs. Coordinates production low among different entities of the enterprise, the retrieval ofstorage_material, andthetransportationofparts.

The Enterprise level is concerned with the overall _process, without

looking

at the small details.

Since SSM and P&PE needto look atthe _{process, product, market,} sales and _suppliers, it also

needsanoverallview oftheenterprise.

ERP,

as stated in the next _pages, comprises all departments and functions. It takes into account

information fromeachofthedepartmentsandeachoftheinformationsystems.

3.3.2.

Enterprise

Resource Planning:

According

to

Chang

(Chang, 1998),

Manufacturing

System is an organization that comprises several _{interrelated manufacturing} subsets. Its objective is to interface with outside production

functionsinordertooptimizethe total _productivityperformance ofthe system(production

time,

costs, and machine utilization). The activities of these subsets include

design,

planning,

manufacturing, and control. These subsets are also connected with production

functions

outside the system,such as: accounting, marketing,

financing,

and personnel.

Enterprise Resource

Planning (ERP)

is a _{manufacturing} system whose focus goes

beyond

inventory

control anddistributedmanagement activities. ERPcanbe considered as a mediumto achieve the connection, via computer systems, between the different subsets of manufacturing.

Production decisions affect and are affected

by

areas like engineering, accounting,

human

resource, marketing, and sales, and in order tomake better

decisions,

corporations have to take into account the impact those areas have.

By

_making available the

necessary

information,

_ERP

systemsassureanenhanceddecisions makingprocess

(Hicks,

1995).

It is worth _noting that ERP

is

the result ofthe evolution ofother

manufacturing

_{systems, more}

particularly, Materials Requirement

Planning

(MRP)

and

Manufacturing

Resource

Planning

(MRP II). MRP systems translated the master schedule

built

for the end

items into

_time-phases

net requirements for the sub-assemblies, components and raw materials _planning, and procurement. MRP II evolved as an extension of MRP to

shop floor

and

distribution

management activities. ERP is the

"natural"

engineering,

finance,

human resource, project management and others were added. The firsts to coin this

term,

ERP,

weretheGartner

Group

of

Stamford,

Connecticut

(Hicks,

1995).

Althoughsome authorsdescribe ERP as a collection of software_programs, andothersas a set of

applications, the common concept is that ERP system integrates various enterprise

functions,

automating

front

office

departments'

functions,

and_{making information}availablethroughout the corporation.

"ERP

attempts to integrate all

departments

and functions across a_company onto a single computer system thatcan serve all those different departments'

particular

needs"

(Koch,

1999).

Since integration began as a set of Islands of Integration (where different software programs

serve thepurposes ofthedifferentdepartments and operationswithin acorporation) each works

independently

fromthe others, andthusERP seeks to _unifythesesystems. ERP aims to create a computer environment where all systems of an enterprise or corporation share information

betweeneach_other; allapplications withinthesystemhaveaccesstoacommon

database,

_giving as result a process more effective and less prone to error. ERP software defines a specific application for a specific operation (i.e. payroll, customer _order, scheduling, and product request..

.), "everyoneinthecompanyseesthesame computer screenandhasaccessto the single

database that holds the customer's new

order"

(Koch,

1999). ERP leans on client/server

distributed architecture, RDBMS (relational database management _systems) and object oriented programmingtechnology. The information is accessible

by

who ever need it. "ERPobjective is

to take information from every corporate

function,

it is a tool that assists employees and managerstoplan, monitor,and controltheentirebusiness"

(Cambashi,

1999).

The main goal of ERP systems is to allow the corporation to gain control of their dispersed information sources, incompatible computer systems and multilingual work force.

Also,

ERP

provides:

Information access: features and functions that deliver

fast,

accurate information to users to

enablethem tomakesounddecisions.

Productivity: architecture and tools that increases worker _productivity

by

_automating processes andtasks.

Freedom of choice (open architecture): support for

leading

systems _platforms, relational

databases,

and_operating systems.

Flexibility: tools that are_easy to use, and applications that are_easy tocustomize and_easy to upgrade.

With ERP companies will see integration of enterprise wide information andthe elimination of redundantdata. ERP softwareis designedto model and automate _manyofthebasicprocesses of a company, from finance to the shop

floor,

with the goal of

integrating

information

across the

3.3.3

Manufacturing

Execution

Systems

MESA International

gives the

following

definition

of

MES,

which is widely accepted through outthe

different

MES vendors and enterprises:

"Manufacturing

Execution Systems deliver information _enabling the optimization of production activities from orderlaunchto finishedgoods.

Using

currentand accurate _data,MES guides, initiates, respondstoand reports on plant activities astheoccur._{The resulting} rapidresponse to_changingconditions,coupledwith afocus on_reducing non-value-added_activities,driveseffective plantoperations and processes.MES improvesthereturnon operational assets as well as on-time delivery,

inventory

turns, gross margin, and cash flow performance. MES provides mission-critical information about production activities across the enterprise and _supply chain via bi-directional

communications"

(Davis, 1999;mesa.org).

Implementation ofERP systemsinvolvesmorethan the top-level activities ofacorporation.But

in order for a ERP system to be of benefit for a _corporation, the _{manufacturing} part of the

corporation,(theplant

floor,

production,and_quality

data)

mustbe integratedto thesystem. Here is whereMEScomestoplay.

MES is the link between controls and ERP.

According

to Adasoft

Group,

"A

factory

must be

considered as a whole. The systems for administration, management, maintenance _control,

follow up and commandcannotbe

independent"

(www.adasoft.com). MES works as the bridge between frontoffice_accountingand the

factory

_supervisorycontrol systems and_product, andits the partoftheenterprise'sinformationsystems thatresidesontheplantfloor.

Enterprise Rssowe*

Planning

Systems

,. ring Execution x Systems,

Controlmd

[image:25.554.234.325.379.607.2]

I Collection

Systems

Figure 3.4: Flowofinformation (Raytheon AutomatedSystems;

http://www.esys.com/rec/autosys/sub_erp.htm)

MES provides basic interface between planning and execution systems

(MESA,

1997). This

factors

on work

being

performed. But _also,

interaction

between MES and the Control System

is

very

important:

MES is in

charge ofthe overall

flow

ofthe product or process. The specific

performance of a piece of_equipment, or an _operator,

is

not as important to the MES as to a controller.

That is

why, MES' central _repositorycollects data from various locations within the

factory,

rather than

from

a particular area.

The MES

downloads instructions about the process

operators and machines requiredtocarryoutthe_{manufacturing}operations(See figure 3.5).

Akin

ERP,

MES is

a product ofthe evolution ofMRP andMRP II. MES

is

viewed

by

some as an enhanced version of the functions performed

by

MRP II

(MESA,

1997). The first

manufacturingapplications occurred as a

by-product

ofthecomputerizationof_accounting,more

specific,

inventory

accounting. MRP II

introduced

a _{closed-loop manufacturing} system, emphasized

in

material planning. But MES

improved

the coordination of cross-functional activities, the

development

of a realistic _schedule, and most

important,

the development of

applications with the _capability to monitor the floor activities and _{to continuously} analyze

activitiesinordertoberesponsiveto eventsas

they

occur.

MES

to

Controls Data Flow

Possibilities

Execution Control MES Resource Alloc/Status OperationScheduling ProductionDispatching Document Control Data Collection/Acquisition Labor Management WIPStatus/Traceability QualityManagement Performance Analysis Process Management ProductTracking&

Genealogy Maintenance Management

Process Instructions:Recipes,

WorkInstructions,Part

Programs,OrderSpecific,

MachineUtilization,Work CertificationRequirements

Operator Instructions: Scheduled (predefined)and preventive maintenance,MaterialSafety

Instructions(documents) Machine Operation Instructions

(documents)

Drill Down(Inquiries)Status

Process Status Batch Reports Focus: Product Decision Location: FactoryPlant

Ad Hoc Inquiries MaterialsAnalysis

Events: Time/Date/log/Alarms Data Collectedform_Monitoring

Functions: ProcessEquipment,

Environment, Labor, Material,

Product Parameters.

Monitoringand_Sensing

Process Equipment Environment Labor Material Control Machine Control RegulatoryControl Real-time QC Advance Process Control

Operations Process_Sequencing MachineandProcess

Interaction LaborInstructions Human Machine_Interfacing

Safety Maintenance

Focus: Process

DecisionLocation:

[image:26.553.62.452.278.679.2]

Shop

Floor/PlantFloor

The

primary

goal of _{any manufacturing} execution system is to accelerate the flow of work

throughout the plant floor. MES provides an electronic network forperformance improvement

because

it can monitor production in real-time, giving accurate and recent information to solve situations and avoid production delays or _quality problems

(MESA,

1997).

Otherwise,

production control personnel and supervisors _may take_{many hours} a

day

toresearch the current status of all the

jobs

on the floor in order to solve a problem or to

develop

a work schedule

(Davis,

1999).

MES

delivers information thatenables the optimization ofproduction activities

from

order

launch

to finished goods. Thus MES provides critical information about the

production acrossthe enterprise

(MESA,

1997).

MES providesavirtual production

keeper,

supervisor, quality control and material requesters. It

dumps the _{necessary data} and information into a common database within a computerized system that gives backthe status oftheproduction and theplant floor. This system can be seen as avirtual counterpart ofthephysicalprocess,

by

which onecanmonitortheproducts inamore

efficient and accurate way. Is a real-time

display

of the

factory

performance that provides the

manufacturerwithalookatthe_{shop floor it}can_reallyuseto manageproduction

(MESA,

2000).

Thesystem's core

functionality

is basedaround

tracking

work-in-process

(WIP)

throughdetailed

product_routing,laborreporting,resource and reworkmanagement, production measurement and

datacollection

(Fulcher,

1999).

OneofMESA reports describes

Manufacturing

Execution Systems as the capture ofproduction

knowledgethatoversees andrecords results ofactivitiesin a productionfacility. It gives a

plant-wide view ofthe status and operation of_{processes, materials,} human resources, machines and

tooling, anddescribestheMES system as a set ofdifferentactivitiesthatworktogether tocreate

thesystem

(MESA,

1997).

According

to thisorganization,theseactivities are:

Resource allocation and status: Manages resourcesthatmustbe availablein order for workto start at the operation. It provides

history

of resources and status in real time. It guides what

people, machines, toolsandmaterials should

do,

andtrackswhat

they

are_currently

doing

orhave

just done.

Operations/Detailed Scheduling: _{Provides sequencing based} on _{priorities, attributes,} and characteristics that when scheduled in sequence _properly minimizes set-up. These

sequencing

and

timing

activities for optimized plant performance are based on finite capacities of the

resources.

Dispatching

Production Units: Manages flow of production units in the

form

of

jobs,

_orders,

batches,

lots,

and work orders. Dispatched information ispresentedinthe sequence

in

whichthe work needs to be done and changesin real time as the events occur on the

factory

floor.

It also

has the_abilityto control the amount of workin process at_any point with

buffer

management. In

Document Control:

Controlsrecords or

forms

thatmust bemaintained withtheproduction unit (work

instructions,

_recipes,

drawings,

standard operation procedures, part programs, batch

records,

engineering

change _notices, shift-to-shift communications). Stores historical

data,

and

gatherscertificationstatements of work and conditions.

Data

Collection/Acquisition:

This functionprovides alinkto obtain operational andproduction

data.

This

_{data may be} collected from the

factory

floor either _manually or _{automatically from}

equipment in an up-to-the-minute timeframe. It monitors, gathers, andorganizes data about the

processes, materials, and operationsfrom_{people, machines,} orcontrols.

Labor

Management:

Provides status of _personnel,

including

time and attendance reporting,

certification

tracking,

andthe_abilitytotrackindirectactivities as basisfor activity basedcosting.

Tracks and directs the use of operations personnel

during

a shift based on qualifications, work

patterns,andbusinessneeds.

Quality

management: Provides real time analysis of measurements collected from manufacturing to assure proper product _quality control and to

identify

problems _requiring

attention.

Records,

_tracks, and analyses product andprocess characteristics against _engineering ideals.

Process Management: Monitors production and _{automatically} corrects or provides decision

support to operators for correcting and

improving

in-process activities. It provides interfaces

betweenintelligentequipmentandMESthroughDataCollection/Acquisition. Directs theflowof

workintheplantbasedon plannedand actual production activities.

Maintenance Management: Tracks and directs the activities to maintain the equipment and

tools to insure their _{availability for manufacturing} and insure _{scheduling for} periodic or

preventive maintenance as well as the response

(alarms)

to immediate problems. It maintains a

history

ofpast events or problemstoaidin

diagnosing

problems.

Product

Tracking

and Genealogy: Provides the _visibility to where work is at all times and its

disposition,

this record allows

traceability

of components and usage of each end product. It

monitorstheprogressinunits,

batches,

orlots of outputstocreate afull

history

oftheproduct.

Performance Analysis: Provides up-to-the-minute_reporting ofactual _{manufacturing} operations

results _along with comparisons to past

history,

goals and metrics set

by

the _corporation,

ES Functional Model

A

Sales

&

Service

Supply

Chain

Management

JWIartagemeriti

y

v

A

A

r

Enterprise

Resources

.

Planning

)

A

V

A

A

Product/

N

Process

Engineering

V^

[image:29.553.97.496.101.525.2]

TWswdlstuows.trelwenfunctionsofMESandliikstoothersystems.Furctfcns_msrylink inmifcipte wit wawsbyDfodirt ami ni&

3.3.4

Control Systems

A rough

definition

of

Control Systems is

a system in which one or more outputs are forced to

change in a

desired

manner as time progresses. Its the _entity responsible for measuring, monitoring, and

manipulating

_{production, people,} products and processes

(MESA,

1995).

Control Systems

corresponds to the

factory

floor/process

system.The function ofit isthe use of

all the equipment on the

factory

floor

(hardware,

_software, and _people) in a manner consistent withthe goal of

producing

aproductor process that falls within theparameters set forth

by

the corporation

(MESA,

1997). It collects data from the available resources in order to maintain characteristics oftheoutput constant with a standard.

The function of control people (and control _machines) is to monitor and control their own

operations. To assure that the outputs are in compliance with the requirements set

by

the coordinator: "controls work in real-time, there are always operations _occurring to refine, or correctthe process to maintain desired

tolerances"

(MESA,

1995). Some ofthe resources used

by

the control systems are: Programmable Logic Controllers

(PLC),

Robots, DCS,

sensing

devices,

Computer Numerical Controls

(CNC),

user operator

interfaces,

display

devices,

special

software,andintelligent input devices.

Hence,

Control Systems focus on _sequencing and _manipulating the process to assure that tolerances are kept within defined

limits,

that material flow is maintained and that all of the people, equipment, andresources involved within the process are

fully

utilized. _{Control is only} concerned about the inputs and outputs (or status _points) of the _process, in order to deliver a product within specifications andaprocess without complications.

There aredifferenttypesofcontrol:

Direct control,anycontrolthatiseffected

by

thestructure or preset_settingofthecontrol

device,

without adjustment relatedtoperformance.

Feedback control system, its one that varies its control on output in accordance with a

comparison oftheoutput witha standard. This typeofcontrol canbe: closed

loop

_control, ifthe system is _completely mechanical and the feedback is part of the mechanical _systems; or open

loop

control, ifthere is a _{gap in} the mechanical connection thatis filled

by

human

interaction.

Furthermore,

it can be classified into continuous or intermittent control,

depending

on the

continuityofthe

testing

and correction ofthe system

(Blair,

1971).

In conclusion, control systems are _necessary to collect and process

information

about certain tasks and attributes in orderto maintainthe _{manufacturing} process _running

according

_to what

is

3.4

CORBA, STEP,

DCOM

and

Information

Sharing

One

has

to realize that thecommon elementto the Information Systems ofan Enterprise

(MES,

SCM, SSM, P&PE, Controls,

and

ERP)

is

the data. It does not matterwhich system is going to

interact

with eachother,or

from

whichlevel onthearchitectureinformationcomes

from,

sooner or

later,

thatstored_{data is going}tobeused. The informationwillbesavedina

database,

andit is thispartoftheenterpriseinformationsystemthathas tobeaccessibletoeveryone.

Furthermore,

theinformation

has

tobeencodedinsuch a_waythatfacilitates theuse ofit

by

_any program and _anyclient. Here iswherethe issue begins: theinformation systemhas tobe robust enoughto permit _any type ofdata tobe process (either_{received, send,} ormanipulated) on _any type of _program, from any where in the planet, and in _any possible platform. So

far,

implementations ofdifferent data types in some programs or

by

some languages are

limited;

communication between hardware (or software) that are not compatible is

difficult;

and even physicaldistancelimits thecommunicationbetweensystemsor networks.

Standards like CORBA (Common Object Request

Broker),

DCOM (Distributed Component Object

Model),

andSTEP (STandard fortheExchangeofProduct Model

Data),

are_groupingthe requirements and architecture _necessary to create applications capable of

interacting

between programs despite the different barriers.

They

could be seen as

interpreters,

but

they

are _more,

because these middleware (as

they

are often _called) act as requesters between a client and a service.

STEP,

CORBA and DCOM differ in subtle _{things, but} the core of each is based on the same principle: to create a mediumthatwould allow interaction between different applications. From

these three standards, CORBA has been developed (and thus adopted)

by

more than 200

commercial software

developers,

organizedinwhatiscalledtheObject ManagementGroup.

The developerofDCOM is theMicrosoftCorporation. A Distributed Component Object Model

(DCOM)

isa model for creatingsoftware suchthat_everyapplicationis constructedfrom aset of

components, each of which performs a set of predefined tasks. These components _{may be}

distributedacrossanetwork,orbeonthesame machine.

Ideally,

aDCOMallows componentsto

be invoked transparently,

i.e.,

as though

they

resided on the same machine as the

invoking

component. Components can also interact

dynamically

at _run-time, without _requiring a recompilation to interact with _newly created components

(www.gsia.cmu.edu/bb26/70-45

6/proj

ects/i ava/dcom.htm).

The Standard for the Exchange ofProduct Model Data

(STEP)

is an ISO standards project to

develop

mechanisms forthe representation andexchange of a computerized model of a product

in

aneutral form. Thegoal istoenableaproductrepresentationtobeexchanged without_any

loss

ofcompleteness or

integrity

(Bradford

Smith, NIST;

web.cad.gatech.edu/~peak/step).

However,

even if there is not a universal standard for

information

_{exchange, there}

has

to

be

a

relationship between the developed standards in order to achieve the goal: to process

data in

a

system

independently

of software, hardware or language. The

integration

of

STEP

and the

the twostandards communities. While STEPgains a new implementationmethodin the form of

distributed

_objects,

CORBA

gains

facility

that serves the

broad

domain ofproduct information

(Hardwick,

1996).

3.4.1

CORBA

Definition

The Object

Management

Group

-OMG-with representationsof more than two hundredsoftware companies (since

1989)

has been

developing

standards and

technology

for object oriented distributedapplications underthenameCommon Object Request Broker Architecture -CORB

A-(Seetharaman,

1998;

Orfali,

1997;

Otte,

1996).

CORBA is a set of standards or protocols for communication _{among heterogeneous} systems

(Murphy, 1998, Seetharaman,

1998; Orfali,

1997). CORBA gathers the specifications from the

Object Oriented technology. The goal _{is for every} software or computer application to be designed and developed under the CORBA specifications, and _thus, be capable of _sharing

information with one another. The architecture described using CORBA allows interaction of

components independent of the

designers,

the platform

they

are _{running on,} the language

they

are written

in,

andwhere

they

are executed

(Seetharaman, 1998; Siegel,

1998).

The DDL language andthe ORB interfaces are the main parts of

CORBA,

and are described in

the

following

segments:

Object Request Broker (ORB): The Object Request Broker

(ORB)

is software that acts as an

intermediate between the client and the server, it manages the client requests and hides the

location andimplementation details ofthe serverfromthe client

(Seetharaman,

1998). The ORB

is thatobject bus whererequests are_made, and responses _received, fromobjects located

locally

or_remotely

(Orfali,

1997).

A CORBA object models a real-world object and consists of data and methods that _{may be} invoked on it

(Seetharaman,

1998). These objects are packaged as

binary

components that

remote clients can access via methodinvocations Becauseofthisobject

infrastructure,

it iseasier forcomponentstobemore_{autonomous, self-managing}and collaborative

(Orfali,

1997).

Interface Definition Language (IDL): IDL_{is necessary}tocode

information

of an objectintoa set

ofinterfacedefinitions. This interface definition specifiestheoperations theobject

is

preparedto perform, theinputand output parameter eachrequires, and_any exceptionsthat _{may be}generated

along the way. With IDL developers can define interfaces and

data

structures that can later be

retrieved_usingahigh level language

(Otte,

1996; Siegel,

1998).

As Siegel explains, the OMG IDL compiler uses mapping specifications to generate a set of

method invocations from the IDL operations. Developers refer to the

OMG IDL file (this

containsthedefinitions ofinterfaces theclient orserver

implementation

willsupport) and usethe

language mappings to generate the _{corresponding} set of method

declaration.

After

compilation

the skeleton is ready to make the right calls to invoke operations on the object

implementation

OMG IDL is usedto define

interfaces

and

data

_{structures,but}nottowrite algorithms. IDL

is

use

to generate source code for the

desired programming

languages. At this moment IDL has

language-mapping

specifications for

C, C++, Java, Smalltalk,

and Ada. But the greatest advantage of _{using IDL}

is

that it

frees CORBA

applications from

being

restricted to _any

particular_{programming language}

(Mowbray, 1997; Orfali, 1997; Otte,

1996; Siegel,

1998).

IDL supports location

transparency,

this means that a remote distributed object can not be

distinguish in its invocation from a local component.

Also,

IDL keeps the system unaware of

changes in the implementation of the software components and the physical allocation of

components until run-time.This isalso afeaturecarried out

by

ORBs

(Mowbray,

1997).

EventhoughIDL isnotthe