feat: new validations

docs/roadmap.md

@@ -20,9 +20,64 @@ When features are requested, we will describe the work to be performed in the se
 
 The following features are currently requested:
 
+* Additional Validations
 * Ability to set 'number of approvals' to zero, enabling instant updates (4 days)
 * Ability to make automated submissions using an API
 
+### Additional Validations
+
+The following additional features are necessary:
+
+* Frontend Formulae
+* Regex Rules
+* Custom Functions
+
+The above rules will apply only at frontend, and will be configurable in the MPE_VALIDATIONS table.  The values will appear as part of the [editors/getdata](https://code.datacontroller.io/getdata_8sas_source.html) service response in the `dqrules` object.
+
+**Frontend Formulae**
+
+An example of a simple rule would be:
+
+```sas
+  REVENUE = PRICE * VOLUME
+```
+
+How to apply this in Data Controller?  Let's consider a table as follows:
+
+|ITEM|PRICE|VOLUME|REVENUE|
+|---|---|---|---|
+|PAPER|4.20|100|`= PRICE * VOLUME`|
+|PEN|61.02|1,971|`= PRICE * VOLUME`|
+
+The plan here will be to introduce [hyperformula](https://hyperformula.handsontable.com/guide/demo.html) into HandsOnTable.  We have confirmed with support, and it is included in our OEM plan.  It will allow a library of ~400 functions and advanced excel-like behaviour.  
+
+HyperFormula requires cell references to operate (rather than named variables), eg as follows:
+
+|ITEM|PRICE|VOLUME|REVENUE|
+|---|---|---|---|
+|PAPER|4.20|100|`= B1 * C1`|
+|PEN|61.02|1,971|`= B2 * C2`|
+
+For ease of use, and to avoid the need to hard code a particular column order, the frontend should perform replacement of the variables for each Formula cell.  For instance, replacing ` PRICE ` with ` B1 ` and ` VOLUME ` with ` C1 ` in the first row (and with ` B2 ` and ` C2 ` in the second row respectively).
+
+To avoid clashes with names that match function names (eg, `MATCH()`) each named variable **must have a leading and trailing blank**. 
+
+There would be two types applied:
+
+* `HARDFORMULA` -> Column is readonly 
+* `SOFTFORMULA` -> Column can be changed by the user
+
+**Regex Rules**
+
+There are two types of rule we can apply in the form of regular expressions:
+
+* `HARDREGEX` -> If the value fails the rule, the data cannot be submitted (turns red)
+* `SOFTREGEX` -> If the value fails the rule we change the cell colour to yellow (as a warning), but can still submit
+
+**Custom Functions**
+
+There may be a requirement to implement a non-standard function, eg to return the value of the logged in user.  For that we can implement a validation rule named `CUSTOMFUNC`.  These functions will be built / tested / documented and packaged by the Data Controller team and shipped inside the product.
+
 
 ### Set Approvals to Zero