All Presentation Material Copyright Eurostep Group AB ® On Reference Data Libraries for Product...

All Presentation Material Copyright Eurostep Group AB

®

On Reference Data Libraries for Product Life Cycle

Support

David Price6th NASA-ESA Workshop on Product

Data Exchange, April 2004

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Topics

• AP239 Product Life Cycle Support• DEX architecture• Implementing a DEX• What is OWL?• Future and conclusions

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What is AP239?

• Product Life Cycle Support (PLCS) is a modular STEP Application Protocol for complex assets (e.g. ship)– Configuration Management

• As-Designed, As-Realized, As-Maintained

– Support Engineering• Support Required (activities, tasks, resources)

– Resource Management• Spares, Who/what/when

– Maintenance and Feedback• Failures, Replacements, …

• The above is a vast over-simplification

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PLCS Approach Fundamentals

• In ISO, standardize flexible data model that can be tailored using Reference Data

• Data Exchange Sets (DEXs)– Create “usage guides” for subsets of AP239 – Create “standard” Reference Data as a basis for

implementation– Standardization in OASIS is planned

• Allow organization-specific extension to the standard Reference Data for further tailoring

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The STEP ArchitectureApplication Activity Model

- What process do I want to support?

Application Reference Model

- What are the information requirements of the activity in industry terminology?

Application Interpreted Model

- How do I model the required information using STEP and EXPRESS?

Assembly Components

Components of a STEP Application Protocol

Implementation Method

- What implementation technology do I need?

Design

Build

Test

definition

relationship

assm_rel

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The Modular STEP Architecture

Common Resource Schemas

Activity Model

Application Protocol

ARMMTAIM

ARMMTAIM ARM

MTAIM

ARMMTAIM

Normative Referenceto Application Module

ApplicationModules

Use individual entity types

Use entire module

MT= mapping table describes what AIM entity types are used to exchange what ARM concepts

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Reference Data

PLCS Requirements The red specializations do not appear in the actual AP239 schema

AP239 ISO Schema

Instead, they appear in Reference Data Libraries

How do AP239/RDL relate?

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DEX Architecture

• STEPmod is the STEP Modules Repository– AP239 PLCS ISO standard is specified here

• DEXlib is where DEXs are specified– DEXs group and tailor “Capabilities”– Capability defines subset of AP239 EXPRESS,

reads from STEPmod and allows usage guidance to be added

• Capabilities are reusable between different DEXs

– An XML Schema for data exchange is generated from each DEX

– DEXlib is also where PLCS standard Reference Data is defined

• STEPmod and DEXlib are XML-based

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STEPMod

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DEXLib

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STEPmod-express schemas-text descriptions

DEXlib-capability

-dex-rdl selection

Standard ReferenceData Library

allowedclassification

adds usageguidance to

Creating the DEX

DEX XML Schema

ISO Standard EXPRESS to XML Schema mapping

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Creating the DEX

STEPmodISO 10303-239

The PLCS standardEXPRESS information model

DEXlib

Extract:• model defns.• model subset

Library of DEXsA DEX:• Subset of AP239 EXPRESS + XML Schema• for contracting• for software conformance • usage guidance

MODRDL

PLCSstandard

RDL

Defines RDL applicability

Create usingProtégé

Class hierarchy

Extend through sub classes

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When Implementing a DEX

• Organizations will likely specify extensions to the Standard Reference Data– Extension is defined by declaring organization-

specific Classes as subclasses of the standard Classes

– So, there are likely two or more RD libraries used in a DEX data exchange1. The standard RD library2. The organization extensions library

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OASIS DEXs-Capability

-DEX-RDL selection-XML Schema

Standard ReferenceData Library

MoD ReferenceData Extensions

DEX-based XMLdata exchange file

System A

System B

subClassOf

classification

translateto

translatefrom

allowedclassification

classification

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What to do about Reference Data?

• We were contracted by UK MoD to do a survey of candidates for Reference Data

• Goal– Determine the best approach for Reference Data

when applied to PLCS DEX data exchange

• Scenario– MoD has a specific business process to automate

using PLCS/DEX-based data exchange

• Technical Assumptions– Exchange based on AP239 EXPRESS->P28 XML– Enable inclusion and reference to RD– Standard RD is extended in implementing

organization

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Requirements arising…

• Create and manage standard RD• Define what RD is used for what schema

element• Enable local extension of standard RD

– Local extensions come from elsewhere in industry or within local organization

– Possible later integration of local into standard RD

• Support implementation of pre- and post-processors– RD may be embedded, exchanged or referenced

• Support implementation of business process/rules– e.g. select, export, transfer, verify, import, report

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Initial Analysis

• Nothing to offer– OASIS had nothing really supporting RD– OMG had nothing really supporting RD

• although UML Profile for OWL is in-process

• Real candidates– 15926-2– PLib– 10303-54– W3C OWL– DEXLib DTD

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Our Conclusion

• While any of the candidates could be made to work, for our set of requirements OWL made the most sense

• In fact, we’ve also concluded that a specific set of tools should be used– Stanford University Protégé with OWL plug-in– Open-source, platform independent (Java)– Pre-load with template containing RDL,

schemas, etc.

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What is OWL?

• The World Wide Web Consortium (W3C) created the HTML and XML standards

• OWL is a next-generation language standardized in the W3C. – its purpose is to add “semantics” to the Web

• Therefore, it can be distributed and is Web-enabled and does not assume a single source for everything

– In concept, it is very much like other data modelling languages (it calls models or schemas “ontologies”)

• class, subclass, property, property type, instance/individual

– it supports added set theory and logic-based statements about the classes and individuals

– it has more than one syntax, XML being one

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Classes and Property Restrictions

Class and subclasses

Properties of Class

Property Restrictions

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OWL Instances/Individuals

Instance of Class “Person”

Property Values

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Why this approach?

• OWL satisfies RDL modeling requirements– Class, multiple inheritance, properties, datatypes,

instances, reuse of models– When UML Profile for OWL ready > Graphical RDL

• OWL satisfies RDL IT requirements– XML syntax, Web enabled– Easy map from 15926, 10303-54, etc.

• Other factors– OWL will win in the market

• Industry and academic support• Open-source tools available

– People outside of SC4 know OWL, not 15926 or PLib

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Standard Refdata as OWLClasses

MoD Refdata Extensionsas OWL Classes

-added refdata classes-added refdata/express usage

DEX-based XMLdata exchange file

subClassOf

classification

classification

AP239 Schemaas OWL Classes

subClassOf

subClassOf

Details of RD Relationships

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Some Reference Data in OWL

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The EXPRESS/RD OWL Link

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More on “Why this approach?”

• For business process and rules, reasoners seem like they have potential use

• While PLCS DEX exchange isn’t “Semantic Web”, this lays the foundation for future PLCS Semantic Web applications

• Makes “STEP” RDL usable by non-STEP applications

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Use of RDL plus inference

Class: FamilyCarType Prop: Service interval = 10000 KmClass: FastCarType Prop: Service interval = 6000 Km

RDL

Onboard Engine management system

Maintenance Planning SystemIf Km since last service > Service Interval then do service

A FastCar

A FamilyCar

Onboard Engine management system

7000 Km since last service9000 Km since last service

Example of STEP, RDL and Inference Engines triggering processes

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Use of RDL plus inference

• On board engine management system on a car sends file to Maintenance Planning System

• File contains Type of Car and Kms since last service (mileage)

• Maintenance Planning System looks up type of car in RDL and gets Service Interval property

• Inference engine rule triggered on Service Interval property and mileage and schedules a service

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Why this toolset?

• Protégé meets OWL/RDL modeling requirements– Can reuse existing ontologies (e.g. Dublin Core for

identification and versioning)– Can create classes, properties and instances– OWL plug-in supports import/export/database

• Open-source GUI, API, database backend, reasoners– Uses HP open-source Jena API– Can add STEP-specific RDL plug-in if that becomes

necessary

• Widepsread use (14000+ downloads)

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The Obvious Concerns

• Semantic Web is still research– Approach doesn’t depend on Semantic Web

technology– Using OWL as a modeling framework, the way 15926

is a modeling framework

• OWL is not an ISO/SC4 standard– Absolutely true! However, even a researchy W3C

standard like OWL is more widespread than EXPRESS

• Have I wasted all my investment in STEP?– Absolutely not. Without the prior work, we would not

be in a position to quickly take advantage of OWL.– Taking advantage of 15926 RDL– We can translate OWL to EXPRESS or 15926 or …

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Conclusion

• The flexibility defined in the PLCS/DEX approach allows it to be used across a wide domain– However, that flexibility means PLCS/DEX implementation

depends on Reference Data

• The W3C OWL language provides very good capabilities for defining, reusing, publishing and relating “models” and “reference data”– By being Web-enabled, RDLs can be linked and distributed– OWL also enables the future use of logic engines as part of

PLCS/DEX implementations

• The use of XML for the exchange file and OWL for the RD puts PLCS/DEX squarely into the mainstream, both now and in the future

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