update README.md

README.md

@@ -52,7 +52,8 @@ Second, "Relation" tables, for example, the `Relation_Position_ProjectType` tabl
 | 3           | 3               |
 
 Third, "Data" tables, for example, the `Data_ProjectSize` table:
-* There can be multiple index columns.
+* There can be multiple index columns. 
+* For timeseries input, besides the `id_` index columns, `tab2dict` also has `period` as a usable index column name.
 * The `unit` column is optional.
 * The name of the last column must be `value`.
 
@@ -65,6 +66,7 @@ Third, "Data" tables, for example, the `Data_ProjectSize` table:
 | 2           | 3               | Euros | 80    |
 | 3           | 3               | Euros | 50    |
 
+
 ### TabKey
 
 `tab2dict` provides the base class `TabKey` that has to be inherited and extended according to the input table columns. 
@@ -83,8 +85,15 @@ class TestTabKey(TabKey):
 ```
 
 As shown, the attributes of the `TestTabKey` class are same with the column names in the input tables. 
-They must always start with `id_`, also as shown above. 
-Furthermore, to include timeseries table, `tab2dict` also has `period` as a default column name.
+They must always start with `id_` (or `period`) as shown above.
+
+### Summary
+
+* When converting a table to a `TabDict` instance (`tdict`), the index columns are automatically identified and recorded as its `key_cols`. 
+* Users can use `TabKey` instances (`tkey`) to fetch data from the dict, as long as the `tkey` knows the values of the `tdict`'s `key_cols`.
+* The `tkey` can know more than necessary, which means
+  * removing an index column from an input table will not cause code changes;
+  * adding a new index column in the input table may neither, as long as the `tkey` knows the added column. 
 
 ## Dependencies
 

setup.py

@@ -6,8 +6,8 @@
     version="0.0.1",
     description="tab2dict supports data handing in developing scientific software.",
     long_description="`tab2dict` supports data handling in developing of scientific software (i.e., models). "
-                     "It can convert predefined input tables (`.xlsx` or `.csv`) into `TabDict` instances. "
-                     "Then, the items therein can be fetched by `TabKey` instances.",
+    "It can convert predefined input tables (`.xlsx` or `.csv`) into `TabDict` instances. "
+    "Then, the items therein can be fetched by `TabKey` instances.",
     long_description_content_type="text/markdown",
     url="https://github.com/SongminYu/tab2dict",
     author="Songmin Yu",