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Auto-Generation of EASY5 Models Using XML Data
Brian Ummel EASY5 Product Support March 16, 2000
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What does Auto-Generation of Models Mean?

• Standard method of building an EASY5 model is
• 1. Look up data where it exists (CAD system,
  schematics, documents, or some other analysis
  tool)
• 2. Convert the representation and data to the
  form EASY5 needs
• 3. Hand build the corresponding EASY5 model by
  hand
• The EASY5 GUI tries to make this process as
  simple as possible but building a large model is
  still a lot of work
• Question Why cant we automate the creation of
  EASY5 models?
• Answer Lots of reasons
• Most obvious The current EASY5 model file format
  makes it difficult

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Current Model File Format

• The current model file format (i.e. the format of
  files with names of the form model_name.mf.nn) is
  essentially a memory dump of the C structures
  used by EASY5x at run time.
• Typical piece of an EASY5 model file
• 0 -1 0 2 1 1 1 1
• 1
• 0 1 1 0 1 3320.0 3950.0 3480.0
• TZAC
• Nozzle\Dynamics
• 17 20 997 4096 0 -1
• 9901181617
• 1 0 8
• 0
• 1 0 9
• 0
• 23
• 23
• te 0
• pa 10 0.000000 1.000000
• fo -1
• As most of us have learned the hard way, even the
  smallest mistake in this file will result in
  EASY5x being unable to read the file.

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Why We Use the Current Format

• Historical Reasons
• The first implementation of EASY5w used Apollo
  Metafile Graphics which had its own file format
• Efficiency Reasons
• The current format can be read directly into
  memory without any interpretation or conversion
• Even so, it is not all that fast for very large
  models
• Because of the efficiency issue, the current
  format will be probably be supported for some
  time.
• So (at least for now) were talking about an
  alternate format for importing models into EASY5.

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Choosing an Import File Format

• The import file format must be
• Easy to write
• Completely specify the data being imported
• Not require that the model be completely
  specified
• Easy and unambiguous to read
• Amenable to changes required by future EASY5
  enhancements
• Our primary tasks were
• 1. Inventing a rich but forgiving syntax
• 2. Writing a parser for that syntax
• Then along came XML

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What is XML?

• XML is a tagged markup language
• Tagged means that the data in the file is labeled
  with names indicating the meaning of the data
• Labels are tags very similar to tags in HTML
• Significant Difference XML allows you to define
  your own tags
• Syntax is consistent and very clean - we dont
  have to invent one
• XML is an ASCII file format
• Means easy transfer of data between machines
• Free field format is very forgiving
• XML is a W3C standard for information transfer
  over the World Wide Web
• Parsers are widely available
• XML files are readable by other applications
  (e.g. Web Browsers)

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XML is an Object Oriented Language

• Each element (a tagged entry delimited by angle
  brackets lt and /gt or by lt namegt and lt/namegt)
  represents an object
• Attributes and members specify the properties
  of the object
• EASY5 objects are primarily components and
  connections
• In XML an EASY5 library component looks like
• ltcomponent name LA1 xloc 3200 yloc
  2800 gt
• ltlibref library gp libmember LA /gt
• ltinput id GAI name tempSensor_gain
  value 10 /gt
• ltinput id TC name tempSensor_timeConstan
  t value 0.03 /gt
• lt/componentgt
• A port connection looks like
• ltconnection from_component IN1 to_component
  LA1 gt
• ltport_connection from_port 2 to_port 1
  /gt
• lt/connectiongt

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XML can be Validated

• Very easy for a XML parser to determine if a XML
  document is Well Formed (ie the punctuation
  is correct).
• More importantly, the XML specification includes
  a provision for specifying a Document Type
  Definition (DTD) which
• Is a formal definition of the syntax of a
  particular type of data file expressed using XML
• Can be used by publicly available XML parsers to
  determine if a file is valid
• Usage of attributes versus members for
  expressing properties of elements is driven by
  the constraints on what is valid.
• The format of an EASY5 XML model file is
  specified by a file called easy5_model.dtd
• The current program which reads EASY5 XML files
  and produces EASY5 metafiles is called ezxml.exe

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Status of The EASY5 XML Project

• The current prototype version of ezxml can
  import
• Flat models (no submodels)
• Library components (not Fortran or C components)
• Component locations
• Port connections (not custom connections)
• Parameter values of inputs
• User defined names
• The submodel structure will be supported next
  (this summer)

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Plans for The EASY5 XML Project

• Current Project
• Enhance the EASY5 model DTD to be able to specify
  everything in the current model file
• Have the import program support the full DTD
• Were looking for opportunities to test this work
• Under consideration
• Write an export program to support conversion of
  EASY5 models into other types of models (such as
  code generators like GSDS)