EcoService Models Library (ESML)

ESML Data and Guiding Concepts

< Back

What is the difference between EMs, EM applications and EM runs?

When gathering information about EMs from the literature, the available source documentation may offer several depictions of the same model, or of very similar models, raising the question of how to present the information in ESML – as one entry or several? 

Most entries in ESML describe individual applications of EMs. Since model formulations often change from one application to the next, focusing on a specific application minimizes the problem of model versioning. Applications also include valuable information on context and often on uncertainty as well. Drawbacks of focusing on applications include (a) the inability to include all applications, and the possibility of skewing a user’s understanding based on examples chosen and (b) the possibility that model updates are not reflected.

The ESML descriptor “Method Only, Application or Run” allows the following options for describing each ESML entry:

Options

Explanations

Method only

This entry describes a modeling method only, without any information about application.

Method + Application

This entry describes a modeling method and a specific application of the method.

Method + Application (multiple runs exist)

This entry describes a modeling method and a specific application of the method; additional ESML entries have also been made showing data from multiple runs associated with this application

Model Run Associated with a Specific EM Application

This entry describes one of several model runs associated with a specific application of an EM. 

Method only is selected when either of the following situations holds:

  • a source document describes only the methodology associated with the EM, and no corresponding application is available
  • the available application does not use the full range of variables described for the EM.

In the latter situation, two EMs should be created – one for the method only and one describing the (limited) application.

When information is found regarding two or more uses, these questions are used to determine which option to use:

  1. INDIVIDUAL SUFFICIENCY: Is sufficient info available about each model use individually (such as separate predictor and/or response values, goodness of fit statistics, or validation statistics reported) to warrant making separate entries to ESML?
    1. No – enter as single EM (Method + Application)
    2. Yes – continue
       
  2. ORIGIN: Does the information about the multiple model uses all originate in the same data collection and modeling effort (for example, as evidenced by their origin in the same document or research effort)?
    1. No – Enter as multiple, related EMs (each as Method + Application)
    2. Yes – continue
       
  3. VARIABLE UNITY: Can all the model uses be described in terms of the same set of predictor and response variables (although variable values may change between uses) and the same variable relationship diagram?
    1. No – Enter as multiple, related EMs (Method + Application)
    2. Yes – Enter as one “Parent EM” (Method + Application [multiple runs exist])
      and multiple “Run EMs” (Model Run Associated with a Specific EM Application)