What does it mean when EMs are “related?”

Some EMs are “related”

In ESML, EMs may be treated as “related” for a number of reasons having to do with model version, application, or segmentation.

Related EMs may be similar versions

An EM record in ESML may describe a model without describing its application, but most EM records describe both a model and a specific application of that model. 

When multiple applications of the “same” model are described in the literature, it is difficult to verify that the mathematical structure of the model actually is identical across the applications, since changes in version or subroutine implementation may have occurred.  Therefore, ESML assumes they may differ in structure and describes them as “related.”   Models are judged to be “related” if there is a developmental thread; they may be sequential versions, or one may include some or all of the other. 

Related EMs may represent different applications of the same model

When information is available about multiple uses of a given model, the way these uses appear in ESML depends on several factors.  If few details are provided about how the multiple uses differ from one another (such as differences in variable values, goodness of fit or validation) then a single EM is described.  But if information does suffice for multiple entries, then a determination is made whether to enter the different uses as separate applications of the model or as “runs” pertaining to the same application.  If the model uses are all part of a single data-gathering and modeling effect (and can all be described in terms of the same set of variables) then they may be treated as runs.  A “parent” EM is then entered that includes all the information that is constant across the runs, and “run” EMs (as many as needed) are entered to describe each run.  But if they come from different modeling studies (or differ significantly in their predictor or response variable set), they would be considered separate applications and entered as separate, but “related,” EMs. Learn more about the difference between EMs, EM applications and EM runs.

Related EMs may be separable segments of a larger model

Sometimes a given modeling approach entails several, potentially separable computational procedures.  When entry is made to ESML, these procedures may be kept together and entered as a single EM (and in this case, the outputs of one procedure, which serve as the inputs to another procedure, are classified as “Intermediate [Computed] Variables”).  If instead each procedure is judged to be individually useful to the ecosystem services modeling community, the procedures may be entered individually as separate but “related” EMs; separation can increase their visibility in ESML searches.