Design Patterns for Integrating Product and Process Models

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Design Patterns for Integrating Product and
Process Models

• The C.R.I.S.T.A.L. Project
• (Cooperative Repositories Information System
  for Tracking Assembly Lifecycle)CERN,
  LAPP(Annecy), KFKI(Budapest), UWE(Bristol)

CHEP2000 Padova, February 2000
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Motivation for Design Patterns

• There are many concepts that support software
  construction. However most of these programming
  paradigms and methodologies focus on creating
  software from scratch.
• Traditional software methods do not tell you how
  to solve individual software construction
  problems.
• Solving such problems is left to intuition and
  experience.

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An Observation

• When experts work on a particular problem it is
  unusual for them to tackle it by inventing a new
  solution which is completely distinct from
  existing ones.
• Where possible they reuse solutions that have
  worked in the past.

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What is a Design Pattern ?

• A Design Pattern
• is a solution schema expressed in terms of
  objects classes for recurring design problems.
• Describes (UML) the elements that make up the
  design, their relationships, responsibilities and
  collaborations.
• Describes heuristics for use applicability.
  (Not modeled in UML)

Problem
Solution
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What is a Design Pattern ? cont..

• A Design Pattern
• Documents proven design experience
• Specifies concepts above the level of individual
  classes and objects
• Provides a common vocabulary and concept
  understanding. Patterns have well known names.

Problem
Solution
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A Design Pattern

• Is NOT
• About designs such as linked lists, trees, hash
  tables that can be encoded as classes and reused.
• and does not imply a mapping to code generation,
  code execution, code portability, code
  customization, code reusability. (Framework
  customized design patterns implemented in an OO
  language)

Problem
Solution
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The Problem Domain

• The design of a production assembly control
  system(CRISTAL) for the construction of the CMS
  ECAL detector using workflow(WfM) product data
  management (PDM) techniques.

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Design Complexity

• System complexity (Millions of parts, Terabytes
  of data)
• Long running and distributed activities
  (1999-2006 CERN, Italy, UK, Russia, China)
• Detector evolution versioning.
• Interoperability with other (legacy) systems and
  future systems yet to be built.
• Generic application to assembling other types of
  systems.

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Managing Complexity

• To manage the complexity changing requirements
  we have built an object oriented architecture
  using OO Analysis OO Design techniques which
  leverage the power of
• metamodels and metamodeling
• multi-layer architectures
• design patterns
• Use the UML to describe the software
  architecture.

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Metamodeling
Set of constructs for OO information modelling
meta types meta relations meta schemas
Defines a language for specifying metamodels
Defines a language for specifying a particular
information domain.
types type relations type schemas
Domain X
Domain Y
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OMG Metamodel Architecture
Layers
Content of a Layer
Architectural Components of a Layer
MOF Meta-Meta-model
Meta-Meta-Model Layer
defines
manages
Workflow Meta-Model
Meta-Model Layer
Meta-Object Facility
defines
manages
Workflow Schemes or Models
Workflow Facility
Model Layer
defines
manages
Workflow Execution
Workflow Instances
Instance Layer
Components
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CRISTAL Metamodel

• At the metamodel layer the CRISTAL metamodel is
  decomposed into several logical packages

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CRISTAL Model
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Patterns for Managing Metamodels
Patterns to Manage Instances
Patterns to Manage Descriptions
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Patterns for Managing Metamodels cont

• Item Description pattern
• Shows the connection between consecutive layers
• Homomorphism pattern
• Due to relationships between ItemDescriptions
• Version pattern
• How to manage the versioning of ItemDescriptions
• Directed Acyclic Graph (DAG) pattern
• When ItemDescriptions are reused for different
  compositions

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Patterns for Managing Metamodels cont

• Enriched Directed Acyclic Graph pattern
• The CompositItemDescription holds semantic
  (layout) for its composition
• Publish/Subscribe pattern
• handles dependencies between ItemDescriptions and
  between different layers
• Enriched Tree pattern
• Tree of Items is generated from an Enriched DAG
• Enriched Homomorphism pattern
• How the PDM/WfM integration can take place

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Concluding Thoughts 1

• At times modeling with UML can be tedious
• Older software engineers at first skeptical of
  design patterns
• The use of design patterns has
• provided a higher level medium for design team to
  communicate, produce and reuse solutions
• identified common PDM and WfM patterns which have
  aided integration of product and process models
• helped manage the complexity

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Concluding Thoughts 2

• The metamodel Architecture Pattern
• Is a proven infrastructure for defining semantics
  required by complex models and has several
  advantages
• Allows building of extensible systems
• Provides flexibility reusability of definitions
• Helps manage complexity
• Allows co-existence of multiple versions of data
• Avoids schema evolution