DECO1007 DESIGN DATA MANAGEMENT

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DECO1007DESIGN DATA MANAGEMENT DATA MODELLING

• Data Exchange

Pak-San Liew September 2004
Key Centre of Design Computing and Cognition
University of Sydney
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contents

• data exchange
• process
• issues
• data sharing
• STEP (ISO 10303)
• IFC-IAI

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data exchange

• the transfer of information
• from one computer system
• to another

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data exchange

• manual re-entry of data
• utilizes the output of one computer system and
  use it as the basis for recreating the same thing
  in the second system
• note time taken to reenter data and to look for
  and correct errors
• use of a standard system
• everybody uses CADX
• direct translation
• save-as / open (different format) within each
  system
• version change of individual system
• use of neutral format
• use of shared product databases
• (data exchange and sharing)

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direct translation
n(n-1) translators
2n translators
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data exchange

• use of Neutral Format
• uses a common format
• develop and agree upon a common specifications
  for data exchange to be supported by all systems
• need two translators
• one to translate from the internal data format of
  the application to the standard (pre-processor)
• one for the reverse translation
  (post-processor)

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data exchange

• known disadvantages
• ambiguous interpretation of standard
• variations in the quality of the translator
  software
• support of different subset
• every CAD system vendor supports a different
  subset of the standard applicable to its own
  products
• geometric data
• the standards are limited to the exchange of
  geometric information and some non-graphical data
  such as connectivity

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data exchange process
(Fowler 1995)
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data exchange process

• translation
• conversion from the internal data structures of
  the sending system into a format suitable for
  exchange
• neutral format exchange
• flavouring
• manipulation of data so that it is more readily
  useful to the receiving system
• may be specific to the target system (e.g.
  specifying the accuracy and tolerances of
  numerical data),
• or may be specific to the use of the target
  system (e.g. mapping the senders convention for
  the use of layers in a drawing to that of the
  receiver)

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data exchange process

• encoding
• structuring of data in a form suitable for
  exchange
• data is normally encoded as ASCII files in order
  to overcome differences between computing
  environments
• may include file compression and data encryption
• transport
• transfer of data across physically separate
  locations
• can be accomplished by physical transfer (sending
  a disk or tape from one site to another), or by
  electronic transfer

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data exchange process

• decoding
• received file is extracted from the exchange
  medium and made available in a form suitable for
  further processing
• flavouring
• data may be manipulated in order to improve the
  quality of the translation
• translation
• data is translated into the internal format of
  the receiving system

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data exchange issues

• translator software
• scope and functionality
• subset of the total specification chosen to be
  implemented in a translator based on the
  capabilities of the CAD system currently in use
• quality
• translators
• standard specifications

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data exchange issues
Scope of Standard
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data exchange issues

• application protocols (APs)
• specify subsets of the standard to be used as the
  basis for implementation
• to overcome the problem of mis-match between the
  subsets of the standard that each system vendor
  selects as a basis for implementing a translator

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data exchange issues

• application protocol concept
• a refinement of the development of subsets
• focuses on the clear definition of the end-user
  or application requirements to be satisfied
• a subset of the standard is chosen that meets
  these requirements
• also relates the subset explicitly to a set of
  industry requirements - specifies the precise
  meaning of each entity

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standards

• STEP
• STandard for the Exchange of Product data
• IFC-IAI
• Industry Alliance for Interoperability (IAI)
• http//www.iai-international.org
• Industrial Foundation Class (IFC)
• http//www.iai-international.org/iai_international
  /Technical_Documents/iai_documents.html
• http//cig.bre.co.uk/iai_uk/documentation/IfcR2x_F
  inal/index.htm

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STEP

• STandard for the Exchange of Product model data
• part of ISO 10303
• industrial automation systems - product data
  representation and exchange

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STEP

• STEP is an acronym which stands for the STandard
  for the Exchange of Product model data. STEP is a
  part of the International Organization for
  Standardization (ISO) and its formal name is ISO
  10303 Industrial automation systems and
  integration -- Product data representation and
  exchange. It was developed by ISO TC184/SC4
  (Industrial data)
• with 28 nations participating or observing, STEP
  is a worldwide effort to develop a mechanism for
  the exchange and sharing of engineering data.
  STEP works towards neutral industrial data
  definitions, representation, and language that
  supports life cycle functions. The use of a
  common exchange format will help reduce
  translation costs and improve quality throughout
  the use of the data. STEP will enable product
  data sharing between software applications
  throughout a product life cycle, different
  organizations involved in a product life cycle,
  and physically dispersed sites within an
  organization
• some examples of commercial implementations of
  STEP can be seen in the digital pre-assembly of
  Boeing 777, and General Motors exchange of part
  designs with its suppliers

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STEP

• document structure
• 7 parts
• published separately
• each part of the standard is classified according
  to its content and numbered collectively
• organized according to a defined document
  structure that reflects the underlying
  architecture of the standard

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STEP document structure
(Fowler 1995)
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STEP document structure

• introductory parts
• part numbers 1 - 10
• describes the overall structure of the standard,
  and the relationships between its various
  elements (not shown in diagram)
• description methods
• part numbers 11 - 19
• defines the languages and methods used to create
  standard representations of product data
• example Part 11 The EXPRESS language
  reference manual

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STEP document structure

• implementation forms
• part numbers 21 29
• defines the standard formats for data instances
  and values, and the mappings between these
  formats and the EXPRESS language
• enforce the separation of data definition from
  implementation within STEP as the data models
  defined in the standard (using EXPRESS) are
  designed to be independent from the various ways
  in which they may be implemented

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STEP document structure

• integrated resources
• a single conceptual data model developed to
  support the common requirements of many different
  product data application areas
• define reusable components that are intended to
  be combined and refined (within an Application
  Protocol) to meet a specific need
• they are not themselves intended for direct
  implementation
• integrated Application Resources
• Part numbers 101 199
• Extends the generic resources to support the
  needs of specific groups of applications

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STEP document structure

• Application Protocols (APs)
• part numbers 201
• define and fulfill the requirements of a
  identified application of product data related to
  a specific industry need
• Application Interpreted Constructs (AIC)
• part numbers 501
• defines the common data modeling constructs that
  are used to fulfill identical requirements that
  exist within the scopes of two or more
  Application Protocols

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STEP document structure

• conformance testing methodology and framework
• part numbers 31 - 39
• provides test laboratories, implementers, and
  end-users with the basis for consistent,
  comprehensive conformance testing of
  implementations of STEP based on the specific APs
• abstract test suites
• part numbers 301
• an abstract test suite should be available for
  each AP
• defines detailed requirements for the assessment
  of conformance and includes a number of test
  cases, that are to be used by all test
  laboratories

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STEP implementation

• implementation level
• data exchange via file transfer
• uses an ASCII file to store data
• data exchange and sharing via database
• uses an underlying database or repository to
  store the data
• data is accessed through a standard interface to
  the underlying database, that allows applications
  to store, manipulate, and above all share the
  data in a standard manner

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data exchange using STEP
CAD System
Data Model
translate
STEP AP
encode
(Fowler 1995)
STEP file
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data sharing and access
CAD System
Data Model
translate
STEP AP
Standard Data Access Interface (SDAI)
database
(Fowler 1995)
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IAI - IFC

• Industry Alliance for Interoperability
• Industry
• Foundation
• Classes

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IAI

• IAI is an alliance of organizations within the
  construction and facilities management industries
  dedicated to improving processes within the
  industry through defining the use and sharing of
  information.
• organizations within the alliance include
  architects, engineers, contractors, building
  owners, facility managers, manufacturers,
  software vendors, information providers,
  government agencies, research laboratories,
  universities and more
• IAI Chapters Organizations within the alliance
  are members of regional Chapters. Currently, IAI
  has Chapters serving Australasia, France, the
  German Speaking countries, Japan, Korea, North
  America, the Nordic countries, Singapore and the
  United Kingdom.

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IFC model architecture

• 4 conceptual layers
• each layer defines a set of model schemata
• resource layer
• provides entities used by entities in the higher
  levels, eg. geometry
• core layer
• provides the basic structure of the IFC object
  model and defines most general concepts that will
  be specialized by higher layers
• interoperability layer
• defines concepts (or classes) common to two or
  more domain models.
• domain layer
• provides set of modules tailored for specific AEC
  industry domain or application type

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(IFC2x2)
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IFC model architecture

• gravity principle
• at any layer, an entity may reference another
  entity at the same or lower layer but may not
  reference one from a higher layer
• references within the same layer must be designed
  very carefully in order to maintain modularity in
  the model design

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references

• Fowler J. (1995).
• STEP for Data Management, Exchange and Sharing,
• Technology Appraisals, UK.
• IFC Specifications
• http//www.iai-international.org/Model/IFC(ifc
  XML)Specs.html
• http//www.iai-international.org/Model/R2x3_fin
  al/index.htm