One of the most common errors (made by STEM novices and experts alike) is failing to set the basis for a resource requirement or transformation input. In previous versions of STEM, the default basis for a requirement from a service to a resource was Connections, and for a resource input to a transformation, the default basis was Installed Capacity. It was not mandatory to set a basis for a requirement or transformation-input when connecting elements, and it was not clearly visible in the tooltip associated with an element that you had used the default basis. This made it difficult to identify what the problem was if your results were not as expected as a consequence of the unset basis not being as intended.
In STEM 7.5, the default basis is None, meaning that if you do not set a specific basis, it is highlighted as an error when you try to run the model. Generally, the Editor prompts you to select a basis when making relevant connections; however, you can also make connections quickly and directly with a preferred basis using a ‘Quick Connect handle’. Any link drawn with a non-preferred basis will be drawn with a different line style to draw your attention to this.
Out of the box, the preferred bases are Connections for a service and Installed Units for a transformation-input. This preferred action for the Quick Connect handle is configurable from the Options menu and also affects which links are drawn differently.
Note: this is a change from the default basis of Installed Capacity for a transformation-input in previous versions of STEM.
When a model is loaded from an earlier version of STEM, any unset bases are explicitly set to the original defaults of Connections or Installed Capacity, respectively.