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XMILE spec implementation notes

The XMILE spec is a large ~80 page document containing a wealth of specifications for compatability with isee software. This document contains notes on where sd.js and libsd diverge from the spec.

Header

  • 'model caption' should be removed.
  • the mix of plural vs. singular is weird and should be standardized.

SimSpec

A key feature of Vensim is savestep. This is useful for many purposes, but not mentioned in the spec.

Includes

Includes will eventually be implemented. There are open questions as to how includes interact with web-based tools. CORS support should probably be mandated to allow in-browser cross-origin requests for XMILE files.

Modules

The spec says a module must have a name="…" attribute w/valid XMILE identifier. If the optional resource is not specified, the name is required to match the name attribute of the submodel. This is an oversight that means we technically aren't allowed to instantite a model in 2 different modules becuase of the 1 to 1 relationship between module name and model name.

We recognize an optional model attribute to specify the name of the model to use for a module.

behavior

Can cause non_negative to propogate, but can't turn that off. i.e. you can't specify non_negative and then have a single stock able to go negative, while you can do the inverse.

4 Model

  • doc: If in plain text, it must use XMILE identifier escape sequences for non-printable characters (i.e., \n for newline, \t for tab, and, necessarily, \\ for backslash), rather than a hexadecimal code such as &#x0A. If in HTML, it must include the proper HTML header. Note this is true for all documentation and user-specified text fields in a XMILE file (i.e., including those in display objects defined in Chapters 5 and 6).
    • HTML is not a subset of XML, so you can't embed an HTML DOM inside an XML DOM.

Variables

  • flow concepts. No documentation, remove them.

Macros

Macros will almost definitely not be implemented. Use Modules.

Identifiers

The formal spec doesn't deal with dotted identifiers. Is Sub_Model.Output a single identifier? What about .Root_Model_Input?

GF

I am just understanding the idea of a 'gf' outside of a variable, and I don't think I like it. It seems much cleaner to me to always have a GF as an attribute of a variable, but allow a variable with a GF but no equation to be considered valid.

Also - the begining of the Doc mentions accessing GFs with square bracket notation, but later on with ()?

FIXME: need to unify the concepts of XMILE GF, standalone GF, and Table in my stuff.

Numbers

FIXME: need to restrict exponent to an integer

Views

page_width + page_height - "The width of a printed page". In what units? This either shouldn't be required, or needs to be much more specified.

page_sequence...

  • lable_angle - counter-clockwise? This is always specified in conjunction with label_side -- how is that useful? Isn't it either/or?

There are 2 possible formattings to use for the display of an entity name, that specified in the 'name' attribute of the <aux>/<stock>/<flow> tag under the <view> section, or the 'name' attribute of the tag under the model section. I am choosing to use the formatting under the model section.