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JSim Projects

This page is for the current JSim version 2.0. Click here for the earlier JSim 1.6 version.


A JSim project is data structure that preserves a related set of models, parameter sets, data sets, plot pages, text-based notes and images. This document discusses JSim projects and some basics of manipulating them in the JSim user environment, although no attempt is made to be exhaustive.




Within the JSim user environment, a modeler may work with and manipulate several types of content when making an scientific analysis:

Each top-level JSim window may contain one or many such items. The JSim project file preserves all content for a single top-level window so that the window can be recreated at a later time in a single operation. Most user-initiated actions within JSim may be thought of as updating the associated project. Users may open multiple top-level windows concurrently, each representing a separate project, and content may be cut and pasted between projects in a simple manner.

Project files are completely self-contained and ( with a few caveats ) contain no dependencies to other files on your system. This allows you to ship an entire project to a collaborator without fear that a cross-referenced file might go missing. Project files are stored in XML format, insuring open interchange, robustness, extensibility and future readability.

Project Content

The project data structure is similar to a company organizational chart with major organizational blocks at the top, and minor content organized within major. The top (1st) level is the project itself. At the 2nd level, the following types of content are allowed:

A top-level window in the JSim user environment represents a single project. Each 2nd level content item appears as a tab within the project window. Plot page tabs appear on the righthand side of the window, all other 2nd level tabs (models, data sets, etc.) appear on the lefthand side. In addition to the 2nd level content tabs, a tab named Project appears on the lefthand side and a tab named "Message" appears on the right. The Project tab allows operations on the project as a whole. The Message tab display error and status messages as JSim runs.

Each 2nd level content item must be given a name that is unique within the project. This name appears on the associated tab. Naming is handled automatically, so the user usually doesn't need to worry about it. However, in large projects, naming can be a useful organizational mechanism. See The Project Tab for more information.


A JSim model contains model source code, compilation state, current parameter assignments, model run-time markup, one or more function generators, and associated notes and images. Model content is organized within a set of subtabs that appear at the bottom of the model tab.

Model source code may be edited within the "Source" subtab. Source is normally written in JSim's Mathematical Modeling Language although other types of code may be used for debugging by JSim internals developers. Historically, MML source code has been stored in free-standing model (.mod) files. .mod files may be loaded into JSim projects in three ways:

.mod files remain useful in some circumstances, but most users will find it simpler to edit MML stored in project files via the JSim user environment.

The model's compilation state is stored in the project. When a project is reloaded, any models that were compiled previously are recompiled. The model's run state is not recreated at project load because, for large models, a model run may often be time consuming and unnecessary. This means that plot pages refering to model data will not be displayed until the associated model is run explicitly by the user.

The assignments of model input variables, function generator controls and numeric solver settings (collectively called parameters) are set in the "Run Time" subtab. Current parameter assignments are stored in the project and restored at project load time. Model inputs may be assigned to numeric constants or to algebraic expressions of other model inputs or function generators (see below) as long as no circular dependencies are created amoung the parameters. Function generator controls and numeric solver settings may be set to numeric constants or selected values, but algebraic expressions are not supported. Additional Parameter Sets may be stored in the project and restored as needed.

Model run-time markup ( RTML ) is a mechanism for customizing the appearance of a model's "Run Time" subtab. This capability is similar that of the XSIM .cf file, but is considerably simplified and more extensible and will, in the future, support drag-and-drop layout. RTML source may be edited in the model's "Customize" subtab.

One or more function generators may be added to a model for assignment to dynamic input variables. Function generators provide the ability to generate many standard wave forms more conveniently than directly in MML, and to import external data (from Data Sets) into a model run. Users create function generators via the "New function generator" item in the "Pages" menu of the model "Run Time" subtab. Each function generator creates a variable in model namespace that can be used in model input assignments. Function generator output is controlled by a set of associated parameters that are stored in the project as part of the current model parameter set or of stored parameter sets.

Numeric solver settings fine-tune the behaviour of JSim built-in ordinary differential equation (ODE) and partial differential equation (PDE) solver algorithms. The default settings will be adequate for most circumstances, but advanced users may wish to tinker with them. The settings may be adjusted via the "Pages" menu of a model's "Run Time" subtab. Numeric solver settings are stored in the project as part of the current model parameter set or of stored parameter sets.

Associated text-based notes (the "Notes" subtab) and images (the "Images" subtab) are also stored with a model. The model's image set may be used by any associated RTML for customized display.

Parameter Sets

When a JSim MML model is compiled, its variables are determined to be either "inputs" or "outputs". Variables declared as "extern" or set equal to a constant numeric value become inputs. Those calculated from other variables become outputs. Model "parameters" are model input variables along with numeric solver settings and function generator controls. A JSim "parameter set" is a collection of parameter names and associated values or assignments. A parameter set may apply to a single model, or to a collection of related models. Parameter assignments for numeric solver settings and function generator controls are constant values. Assignments for model inputs may be either constant values or algebraic expressions of other input values. If algebraic assignments result in circular logic, an appropriate error message will alert the user to the situation at model run time.

The set of parameter values shown in the model "Run Time" subtab are known as the "current parameter set" for that model. When a model is run, the assignments from the current parameter set are used. The "Run Time" tab allows users to modify parameters in a convenient way to examine the model behaviour for different parameter values. Users often find it useful to save a copy of the current parameter set for later recall. This may be accomplished via the "Store parameter set..." action in a model's "ParSet" menu. At a later time, the "Load parameter set..." action (in the same menu) will restore the current parameter set to the previous state.

Since models and parameter names evolve over time, it is possible that some names in a stored parameter set may not correspond to any parameter in the model it is loaded into. In this case, JSim does as best it can, and alerts the user, via the Message tab, of any inconsistencies it finds. Work continues to produce optimally useful messages in this situation.

Important note for new users: A model's current parameter set may be thought of as a work area that is constantly being modified be setting of individual values or reloading from stored parameter sets. It is automatically preserved whenever a project file is saved, and also when a model is recompiled. The latter functionality can be confusing for new JSim users. When the MML for a previously compiled model is changed to reflect new constant values for input variables, these new values merely become the new default values for those inputs. These new defaults are not automatically reflected in the current parameter set (or any other parameter sets). If the user wants the current parameter set to reflect the new model default values, s/he should select "Revert to model defaults" from the "ParSet" menu. This behaviour is somewhat controversial and may be changed at some future time.

Users creating parameter sets are typically contrasting several different parameter sets representing different physical/physiological situations. Because of this, judicious naming of parameter sets tends to be more important that for other 2nd level content. See The Project Tab for information on naming and renaming.

The "Notes" subtab within a parameter set provides ability to add comments, notes or text documentation relating to the parameter set.

Data Sets

Project data sets contains numeric results from experiments, simulations, or other sources. Data sets are usually created by importing external data files, although they can also be created by saving plot page content. A data set contains one or more data curves. Each curve has a name, unique within the data set, by which it is known to the rest of JSim. A curve may have a text description, and an physical unit (e.g. ml/sec). Each curve's data may have any dimension, although 1-dimensional (e.g. time-course) data is most common.

JSim supports several importable data formats. See here for details.

A data set can also be created from a plot page via the "Store project dataset ..." item in the plot page's "File" menu. Data set curves thus created will have the dimension of the data plotted, usually 1-D or 2-D.

Once data sets are created, curves from them may be used in several ways:

The "Notes" subtab within a data set provides ability to add comments, notes or text documentation relating to the data set.

Plot Pages

Plot pages display data from multiple models and/or data sets in several graphical styles. XY line and symbol plots, contour and colormap plots are currently available. In the future, surface plots will also be available. Each plot page contains one or more separately controllable plots. The number of plots in a page is controlled by the "#rows" and "#columns" menus. Initially, only a single plot is created within the page. A new project initially contains a single plot page. Additional plot pages may be added via the "Project" tab "Add" menu.

The upper portion of a plot page, called the "Plot Configurator" allows the user to select data to be plotted and control the rendering characteristics of that data. The lower portion, shows the data either as graphics (the "Graph" subtab) or tabular text (the "Text" subtab).

The 2nd line of the configurator, starting with the label "Data" allows selection of the data to be plotted. The first box to the right of "Data" selects the data source, which may be either a model or a data set. Further to the right is the data selection, where the user may enter the data item, from within the selected data source, to be plotted. Algebraic expressions of data items (e.g. 2*a-b) may be used as well as simple variable or data curve names.

Some plot properties, such as title, axis labels and legend placement can be edited in a point and click fashion within the plot graphics window.

All plot configurator characteristics are stored in a project and are reestablished when a project is reloaded. As noted above, model output data is not available to a reloaded project until the model is explicitly rerun by the user.


Free form text-based notes may be added to a project via the "Project" tab "Add" menu.

The Project Tab

Now that you understand the content of a JSim project, we'll examine the "Project" tab, which gives you overall control of project content.

The main body of the "Project" tab shows a tree structure representing the project content. Currently, only 2nd level content is shown, each item by its assigned name. A more detailed tree may be available in the future.

The "File" menu allows the standard operations of opening an existing project, starting a new (empty) project, saving projects to disk, closing windows and exiting. JSim automatically exits when the last project window closes.

The "Edit" menu allows you to cut/copy/paste content between projects in an intuitive way. Select one or more items in the project tree before executing a cut or copy. Cut or copy before you paste. Paste is most useful between two different projects, but only works with project windows that are part of the same executing program. So if you need to paste, don't start a bunch of separate JSim instances, but rather open new project windows from existing ones. You can see the results of cut and paste operations reflected in the project tree. Note that pasted items may be automatically renamed to insure name uniqueness within the project. Selected items can also be renamed, as desired, from within this menu.

The "Add" menu allows you to add content to the project:

The "Help" menu provides pointers (via the "Message" tab) to various information sources.


In general, JSim project files preserve almost all information about the state of a JSim window so that it can be recreated by any user with access to the file and to the basic JSim distribution. The following lists exceptions to that general rule:

Comments or Questions?

[This page was last modified 14May15, 10:04 am.]

Model development and archiving support at provided by the following grants: NIH/NIBIB BE08407 Software Integration, JSim and SBW 6/1/09-5/31/13; NIH/NHLBI T15 HL88516-01 Modeling for Heart, Lung and Blood: From Cell to Organ, 4/1/07-3/31/11; NSF BES-0506477 Adaptive Multi-Scale Model Simulation, 8/15/05-7/31/08; NIH/NHLBI R01 HL073598 Core 3: 3D Imaging and Computer Modeling of the Respiratory Tract, 9/1/04-8/31/09; as well as prior support from NIH/NCRR P41 RR01243 Simulation Resource in Circulatory Mass Transport and Exchange, 12/1/1980-11/30/01 and NIH/NIBIB R01 EB001973 JSim: A Simulation Analysis Platform, 3/1/02-2/28/07.