将用户定义的逻辑存储在数据库中

Question

I'm designing a database to store information about events that are dynamic in nature. What I mean by this is that, each type of event will have some variables attached to them that changes on each occurrence based on some rules defined by the user.

Let's say we have Event Type A with variable X and Y. In this event type, the user can define some rules that determines the value of X and Y on each occurrence of the event.

An example of a set of rules a user might define:

• On first occurrence, X = 0; Y = 0;
• On each occurrence, X = X + 1;
• On each occurrence, if X == 100 then { X = 0; Y = Y + 1 }

By defining these rules, the value of X and Y changes dynamically on all occurrences of the event as follow:

• 1st occurrence: X = 1, Y = 0
• 2nd occurrence: X = 2, Y = 0
• ...
• 100th occurrence: X = 0, Y = 1

Now, I'm not sure how to store the "user-defined rules" in a database and later query them in my code. Can anyone point me in the right direction? Here's a start:

EVENTS
id;
name;
description;
event_type;

EVENT_TYPE_A_OCCURRENCES
id;
event_id;
X;
Y;

EVENT_RULES
id;
event_id;
frequency; // the frequency in which this rule applies
at_occurrence; // apply this rule at a specific occurrence
condition; // stores the code for the condition
statements; // stores the code for the statements

I'm no expert, please help me solve this problem. Thank you.

Answer 1

Assume following user defined rules stored in table:

-----------------------------------------------------------------
|eventid|occurance|keep-old-x|keep-old-y|x-frequency|y-frequency|
-----------------------------------------------------------------
| A     | 1       | T        | F        | 1         | 100       |
-----------------------------------------------------------------
| B     | 2       | F        | T        | -2        | 0         |
-----------------------------------------------------------------
| C     | 5       | T        | T        | 100       | -3        |
-----------------------------------------------------------------

Lets say before event X = 10, Y = 12. Event = A, ocuuurance = 1, keep-old-x = T, keep-old-y = F, x-frequency = 1, y-frequency = 100

if keep-old-x is T then
        X = X + x-frequency
else
        X = x-frequency
endif

if keep-old-y is T then
        Y = Y + y-frequency
else
        Y = y-frequency
endif

Now, X = 11, Y = 100

You may need to add two more columns to change value of X variable on specific value; as:

--------------------------
|if-x-value| x-new-value |
--------------------------
| 100      | 0           |
--------------------------
| 125      | 5           |
--------------------------
| 150      | 10          |
--------------------------

I hope this helps.