Expository documentation in metadatabase

sift/workspace/metadatabase.py

@@ -11,7 +11,7 @@ SQLAlchemy database tables of metadata used by Workspace to manage its local cac
 OVERVIEW
 
 Resource : a file containing products, somewhere in the filesystem, or a resource on a remote system we can access (openDAP etc)
- |_ Product* : product stored in a resource
+ |_ Product* : product stored in a resource, typically a complete multidimensional observation array with masking and geolocation
      |_ Content* : workspace cache content corresponding to a product, may be one of many available views (e.g. projections)
      |   |_ ContentKeyValue* : additional information on content
      |_ ProductKeyValue* : additional information on product
@@ -19,6 +19,12 @@ Resource : a file containing products, somewhere in the filesystem, or a resourc
 
 A typical baseline product will have two content: and overview (lod==0) and a native resolution (lod>0)
 
+Products fall into family groups (eg G16 ABI B04 toa_reflectance) which typically have their style (colormap etc) running in lockstep
+Products also fall into track groups (eg G16 ABI B04 toa_reflectance ECONUS) which represent a time series of one specific scene being observed
+
+Products typically are imported from external resources, or are derived from one or more products (e.g. algebraic products)
+Derived products may be calculated on-demand in a background thread, similar to imported products being brought into the workspace from an external file
+
 
 REQUIRES
 SQLAlchemy with SQLite