Themis

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Themis

• Sources
• Structural templates and transformations the
  Themis structural computing environment (Anderson
  et al. 2002)
• Structure and Behavior Awareness in Themis
• (Anderson et al. 2003)

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Agenda

• Introduction
• Architecture overview
• The use of Themis
• Themis pros / conts
• Conclusion
• Discussion

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Introduction

• Themis is
• A structural computing environment (Engelbart C
  level work).
• In the same field as Construct, Callimachus and
  Fundamental Open Hypertext Model.
• Not fully implemented when the articles were
  written.

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Introduction

• Themis presents common ways to
• Model data structures.
• Store and load data structures
• Operate on data structures.
• Transform one data structure to another.

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Introduction

• Themis claims that
• Themis provides developers with an easy-to-use
  framework for structural computing
• A Themis structure server can compete with a
  XML-based repository.
• The developers (users) code will be short,
  understandable and maintainable.

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Architecture overview

• The architecture consists of 4 APIs
• Framework -Interface/pattern for the overall data
  structure (not domain spec.)
• Structure server -implementation of the
  framework)
• Template API Define and access named structures
  on top of the framework)
• Transformation API -Transform one template to
  another on top of the framework)

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Architecture overview

• The Framework

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Architecture overview

• Structure server

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Architecture overview

• Data Structure Templates

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Architecture overview

• Transformation mechanism
• Can transform one structure type to another. Type
  a to b.
• Can detect a chain of transformators. If no type
  a to c then type a to b and b to c.
• Structures in the transformation needs to be
  template-based.

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The use of Themis
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The use of Themis

• Initiate a template with Themis template
  initiator
• Initiator gets parameters as a list from the
  user.
• User needs only to specify the list.
• User needs to know what to specify in the list.

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The use of Themis

• Use find(label) to get an element

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Themis pros

• High level of abstraction
• User dont need to know a structure to
• Initiate a new template-based structure.
• Retrieve an Element of a structure.
• Transform one structure to another.
• User dont need to think about persistence.
• Structure and data are not mixed from the users
  point of view, like a XML structure.
• Lines of client side code is reduced.

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Themis conts

• Used to be simple design?
• Template/transformation mechanisms not useful for
  single use of data structure.
• Is transformation plug-ins easy to write?
• Generic structures might be slow
• Is FOHM faster?

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Conclusion

• Structural environments like Themis and
  Callimachus focus on data structures (is in a way
  just constraints)
• Structural computing environments lets the
  developers focus on application functionality.
• Functionality is what creates profit.

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• Comments/Questions/Discussions