Changes between Version 30 and Version 31 of BluePrint/Importer

Timestamp:

01/22/11 12:08:21 (14 years ago)

Author:

Pat Tressel

Comment:

--

BluePrint/Importer

@@ -124 +124 @@
 ==== Data structure uses cases: ====
 
-(This is only about the source schema, not the CSV representation.)
+(This is only about the source schema, not the CSV representation.) In general, a
+normalized relational schema is a directed acyclic graph with a possible exception
+for self-cycles (a reference from a table to itself). Collections of records and
+their key references can also form a DAG. (There should not be cycles in the
+key references even if there are self-references within one table -- it is always
+possible to avoid cycles among records by using relationship tables that
+have outlinks to all the participants.)
 
 - A flat table -- one resource with no components or foreign key references.
@@ -150 +156 @@
   files above.
 
-- A single file with a recursive outer join of all the tables.
-  For 1-N, the data on the "1-"
+- A single file with a recursive outer join of all the tables -- that is,
+  a "flattened" representation of the tables.  For 1-N, the data on the "1-"
   side is repeated in each row along with the separate records of the -N
   side.  For M-N, either side may be replicated across multiple lines in the
@@ -172 +178 @@
 - Any combination of the above.
 
-=== Schema mapping ===
+=== Specifying the schema mapping ===
+
+- If the data uses our formatting, we don't need a schema mapping -- we just need
+  to be told it's our formatting.
 
 - If the source has a schema that does not match ours, a means of mapping from the
-  source's schema to ours will be needed, or will have to be inferred.
+  source's schema to ours will be needed (or will have to be inferred).
   (It is likely, for an existing major source, that we would write the schema mapping.
   For such a source, if we were receiving updates from them regularly, we would want
@@ -181 +190 @@
   on regularly, there may be better means of pulling data than CSV files...)
 
-- If the data uses our formatting, we don't need a schema mapping -- we just need
-  to be told it's our formatting.