There are pretty much 4 predominant types of mapplets in OBIA Infa ETL.
Business Component (ex: mplt_BC_XXX) – These mapplets are used to extract the data from the source systems. They are only found in the SDE folders and start off the majority of the mappings. Within these mapplets, you will find the Source Tables and the Source Qualifier, which has the SQL Overridden. Some SDE mappings might not use these and have the Source(s) and Source Qualifiers straight within them.
Source Adapter (ex: mplt_SA_XXX) – These mapplets are used for source specific transformations, such as standardizing column formats. Since they are source specific, they are only found within the SDE folders.
Analytic Data Interface (ex: mplt_ADI_XXX) – These mapplets are source system independent and resolves the codes (code lookup) for the target table. You will not find much of these, but they are re-usable.
Source Independent Load (ex: mplt_SIL_XXX) – These mapplets are responsible for transforming specific types of columns in the target table. For fact tables, it predominately performs the lookups to the dimensions FK(s) (row_wids). It also functions to do Code-Name resolutions, dimension surrogate key generation via Sequence transformations, SCDs handling of effective dates,…. There are pretty much a lot of transformation logic that is performed in these. Since they are encapsulated mapplets and flagged for upgrades, care must be taken to update these for customizations such as extensions. Refer to ch. 17 within the OBIA config guide for more details on customizing the OBAW.