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A New Philosophy for STEP Implementation

- STEP for the Web (S4W)

David PriceOctober 2003

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STEP for Web philosophy, not religion

• There is a *philosophy underlying this discussion– SC4 made a first foray into “the Web” and replaced

EXPRESS/P21 with DTD/XML• We got free tools and a bigger pool of programmers• However, lots of other new capabilities were missed because

SC4 cares about the “pretty-ness” of the XML (and still does)

– The new S4W philosophy says… SC4 has been missing the forest for the trees

• What is important is what new capabilities the XML enables

*Caveat : This philosophy doesn’t do calculus, so it’s not to be applied everywhere

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The new S4W philosophy

• SC4 should focus on putting the semantics of its schemas/data into the forms new Web capabilities use– Practically speaking, this means others control

the XML– However, by giving up control, implementors

gain the use of new toolkits and capabilities– This may also result in several XML

representations of the same schema/data… but that’s OK! Each has a purpose.

– So, under this philosophy the verbose OWL syntax is far superior to any Part 28 configuration

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Part 25, UML and exff

• Part 25 fits under this philosophy• Translating EXPRESS to UML means

implementors can use powerful software engineering systems– Lowers the cost of STEP implementation– Enables use of languages SC4 standards don’t

support (e.g. Ada, Smalltalk, OWL)– We benefit by giving up some level of control

• In support of this philosophy, Eurostep has started an open-source project called “exPRESS for free”

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exff Problem Statement

• While it's true that– STEP and EXPRESS have been in-work 10-15

years or more, and– STEP has saved organizations time and money

• It's also true that– STEP and EXPRESS have not "taken off" the

way UML and XML have in recent years– In many ways, STEP was ahead of its time– As things stand today, there are many good

STEP models that will not be widely used

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exff Architecture

UMLEXPRESS IDE

Engineering application

application code,database, web service, knowledge base, …

Software development tools

XMIEXPRESSXML

exff

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exff Architecture Details

UMLEXPRESS

XMIEXPRESSXML

XSLTStylesheetProcessor

EXPRESS UMLProject File

WinZIPEEP E to UStylesheet

U to EStylesheet

UML model inXML accordingto XMI standard

EXPRESS schemain XML accordingto Modules Repository

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Possible EXPRESS/UML Evolution

1. UML = SDAI for implementors (Part 25)– Treat UML as just another language like SDAI/C+

+

2. UML = EXPRESS-G for modellers (exff)– Use UML diagrams instead of EXPRESS-G with no

effect on EXPRESS– Could satisfy the need for EXPRESS 3 Operations,

etc.

3. UML = EXPRESS interoperability for all (E 3?)– make them "the same", modellers and

implementors use whatever suits them

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Conclusion

• S4W provides huge opportunities for STEP implementation

• SC4 should focus on the “semantics” that have been agree internationally over the past 15 years– However, SC4 should give up control of many

aspects of the standards involved during implementation

• SC4 should formally adopt OMG and W3C standards for implementation and “interoperate” for modelling where ever possible