Frequently asked questions

Troubleshooting Studio

1. After installing Internet Explorer 7, Studio will not start and reports an error. What is wrong?
2. How do I break a circular reference loop?
3. How do I set the default font for diagrams in Studio 7?
4. When I try to delete a dataset, I receive an error message reading "Cannot delete dataset, it is currently open". What is wrong?
5. Sometimes when I restore my user interface to Normal or Advanced, the layout of the toolbars doesn't seem right. What can I do to fix this?
6. When I open Studio, I receive an error message reading "PS_TC_INSERTMRU is undefined." What is wrong?
7. When I open the Learning Lab in Studio 2003 I receive an error message and all the buttons are missing. What's wrong?
8. How do I create a flow that works in Studio?
9. Can I create models without units of measurement in Studio?
10. Can I use the Spreadsheet Dataset when using Optimization in Studio?
11. How do I export equations to a file?

1. After installing Internet Explorer 7, Studio will not start and reports an error. What is wrong?

The installation of Internet Explorer 7 is not complete until you have restarted your computer. Studio uses Internet Explorer, and is not able to start until you have restarted your computer to complete the installation of Internet Explorer 7.

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2. How do I break a circular reference loop?

In Studio you are allowed to construct a circular loop of auxiliaries and links (for example, A --> B --> C --> D --> A) as long as you have written equations to avoid calculation circularity by introducing delays. In some cases, you might nevertheless experience that you get question mark indicators on all the links in the loop (with tooltips saying "circular reference"). By default, Studio automatically calculates the type, unit, and dimensions of variables. To determine the automatic type, unit, and dimensions of a variable, Studio examines the definition of the variable, but it cannot do this before knowing the type, unit, and dimensions of the variables it references. In a circular loop this will not work, so you need to break the loop of automatic calculations by specifying explicit type, unit, and dimensions for one of the variables in the loop (anyone will do). You do this by unchecking the Auto checkboxes in front of the Type, Unit, and Dimensions fields in the Definition property page for the variable, before providing the type, unit, and dimensions explicitly in these three edit fields. A message box will appear when you push the Apply button. Just answer Yes, and the circular reference indicators should be gone.

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3. How do I set the default font for diagrams in Studio 7?

In Studio 7 you can you set the default font to be used for variable names and other texts in diagrams. The default font is controlled in the Diagram tab of the Options dialog available from the View menu.

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 4. When I try to delete a dataset, I get an error message reading "Cannot delete dataset, it is currently open". What is wrong?

The reason why you receive this error message is that there are open connections for the dataset you try to delete. You need to close all connections for the dataset before you can proceed. Open the Connections window (the Co-models window in versions prior to Studio 7). Select all connections (in most cases there is just one) for the dataset you want to delete, and then select Delete on the shortcut menu or press the Delete key to delete the connections. If you now try to delete the dataset again, no error message will appear and the dataset will be properly deleted.

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 5. Sometimes when I restore my user interface to Normal or Advanced, the layout of the toolbars doesn't seem right. What can I do to fix this?

Sometimes when I restore my user interface to Normal or Advanced, the layout of the toolbars doesn't seem right. What can I do to fix this?
If the layout of the toolbars doesn't seem right after selecting the Restore User Interface command in Studio, you can fix the layout by invoking the Restore User Interface command a second time.

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6. When I open Studio, I receive an error message reading "PS_TC_INSERTMRU is undefined." What is wrong?

The Task Window in Studio uses Microsoft's HTML Help and Internet Explorer (IE) to display its content. Unfortunately, IE contains a bug that causes IE to behave strangely when the temporary internet files cache is full.

To fix this problem, follow the steps below.

1. Open Internet Explorer, and select Options on the Tools menu.
2. On the General property page, click Delete Files under Temporary Internet Files.
3. When Internet Explorer has emptied the cache, you can click OK, close Internet Explorer, and restart Studio.

To reduce the problem (and hopefully remove it entirely), you can reduce the size of Internet Explorer's cache for temporary internet files (available in the same dialog box as the options above).

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7. When I open the Learning Lab in Studio 2003 I receive an error message and all the buttons are missing. What's wrong?

The help system in Studio uses Microsoft's HTML Help and Internet Explorer (IE) to display the help system. Unfortunately, IE contains a bug that causes IE to behave strangely when the temporary internet files cache is full.

To fix this problem, follow the steps below.

1. Open Internet Explorer, and select Options on the Tools menu. When Internet Explorer has emptied the cache, you can click OK, close Internet Explorer, and restart the Learning Lab.
2. On the General property page, click Delete Files under Temporary Internet Files.

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8. How do I create a flow that works in Studio?

In Studio, all variables must be defined with a unit of measurement. In most cases when a flow is not correctly defined, it is due to a unit mismatch between the auxiliary controlling the flow (the flow rate variable) and the level that the flow runs to or from. As long as the flow is a regular continuous flow (the flow is indicated by an empty double arrow), the unit of the flow rate should be compatible with the level's unit divided by time. To exemplify, if your level is a bank account, it could be measured in USD. The flow of interest into the account, payments going out of the account, and similar, should be measured in USD/month. If your level represents a stock of goods, it could be measured in 'crates' (or similar). The flows running into the stock could be orders, while the flows running out of the stock are deliveries. These could be measured in crates/day or crates/week, etc.

The rule of thumb is:

unit of flow rate = unit of level / time

As a new feature of Studio 7, you will receive further assistance in providing a compatible unit for a flow rate variable.

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9. Can I create models without units of measurement in Studio?

Yes, you can. To turn off the units of measurement, select Project Settings from the Project menu, and deselect the option Enforce time unit consistency (Time has Unit in Studio 2003 and earlier). When this option is deselected, you are not required (but you are still allowed) to include units of measurement in any variables.

We do NOT recommend that you build models this way, however. There are a number of reasons for this:

• The time dependence will be built directly into your model. If you change the time step, the model will produce different results relative to the calendar.
• If you use units of measurement for some but not all the variables in your system, there is a great likelihood that some of these variables will receive strange units.
• The built-in units of measurement system assist you in creating valid models. If you turn off the calculation of units, you will loose the automatic model validation capability.

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10. Can I use the Spreadsheet Dataset when using Optimization in Studio?

Yes, you can. However, you must turn off the Continuous data transfer option and use Behavior over time to avoid receiving the error message when clicking Optimize…. To change these settings, follow the procedure outlined below:

Studio 2005:

1. Double-click the Spreadsheet Dataset entry you wish to change in the Project Window.
2. Right-click the Dataset node (at the top of the Spreadsheet Dataset window) and select Properties on the shortcut menu.
3. Click the Layout tab.
4. Deselect the Continuous data transfer option.
5. Make sure that Behavior over time is selected under Category.
6. Click OK to save the changes.

Studio 7:

1. Double-click the Spreadsheet Dataset entry you wish to change in the Project Window.
2. Right-click the Dataset node (at the top of the Spreadsheet Dataset window) and select Properties on the shortcut menu.
3. Click the Misc tab.
4. Deselect the Continuous data transfer option.
5. Click the Time Dependecy tab.
6. Make sure that Time-dependent data (behavior over time) is selected.
7. Click OK to save the changes. 

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11. How do I export equations to a file?

 Studio 7 supports copy of equations as tab-separated text directly from the Equations window (just select the variables and select the Copy command).

In earlier versions, you need to print to a file using a printer driver that generates plain text. You can use the "Generic / Text only" printer that is included with Microsoft Windows. Follow the steps below to install the printer. Note that these steps assume that you have Microsoft Windows XP installed. But the steps are similar for the other versions of Windows.

1. Choose Printer and Faxes in the Start menu.
2. In the new window, select Add Printer in the File menu.
3. The Add Printer Wizard appears. Click Next.
4. Select Local printer ..., make sure Automatically detect ... is not checked. Click Next.
5. Select any local LPT port, e.g. LPT'. Click Next.
6. Select the Generic manufacturer and select the Generic / Text Only printer. Click Next.
7. Click Next three more times and then click Finish.
8. Open Studio and the model you want to print the equations from.
9. Select Print in the File menu.
10. In the Printer section, select the Generic / Text Only printer and check the box Print to file.
11. In the Print what section, uncheck the Diagram box and check the Equations box. Click OK.
12. Enter the full path of the output file, e.g. "C:\Temp\Equations.txt". Click OK. 

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