Data_Tables and Queries

Accessing Internal Data

samples/basic/tutorial/products.kb and products_1.mdb

Some knowledgebases need to reason over data that can be stored in an internal data table. To do this, KnowledgeWright provides data_table objects and the find() function. Data_Tables are generally more flexible than external database tables because each column can contain different types of data, i.e. strings and numbers. Data_Tables are also more powerful because entries can consist of formulas and object names. In this case, the KnowledgeWright reasoning engine is called to determine a value before the find() function returns a value.

Create the Data_Table and Find() Query

To illustrate this, we will query a data_table to determine the upgrade price for a product. First we need to build a knowledgebase with a data_table to contain the pricing information and a fact whose value is the result of a find() function that queries the data_table:

1. Create a new knowledgebase named products.
2. Set the goal in the main knowledgebase object to upgrade_price.
3. Create a new data_table named upgrades.
4. In upgrades, select Column/Add to create 4 columns: product, version, new_product and price. You can drag the column headers left and right to arrange them in the order you would like.
5. Use Row/Add to enter the following data:
   

   old_product	version	new_product	price
   "ap1pc"	"4.0"	"ap1pc"	0
   "ap1pc"	"4.1"	"ap1pc"	0
   "ap1pc"	"5.0"	"ap1pc"	0
   "ap1pc"	"4.0"	"apxpc"	2500
   "ap1pc"	"4.1"	"apxpc"	2500
   "ap1pc"	"5.0"	"apxpc"	2500
   "apxpc"	"4.0"	"apxpc"	1500
   "apxpc"	"4.1"	"apxpc"	1000
   "apxpc"	"5.0"	"apxpc"	0

6. Create new fact named price. For it's value enter:
   find(price from upgrades where old_product = old_product and version = old_version and new_product = new_product)

Ask the Questions and Display the Answer

Our knowledgebase asks the three questions, old_product, old_version and new_product used in the find() function above. Using the answers to those questions, the fact price gets the price. The price is displayed in a short document.

1. Create a new knowledgebase named products.
2. Set the goal in the main knowledgebase object to upgrade_price.
3. Create the three questions:
• A menu_single_choice_display_separate question named old_product, that prompts the user for the last product purchased. The choices are:
  

  rule_text	display_text
  ap1pc	Amzi! Prolog + Logic Server, Personal Edition
  apxpc	Amzi! Prolog + Logic Server, Professional Edition or Commercial License

• A menu_single_choice question named old_version that prompts the user for the last version number purchased. The choices are 4.0, 4.1, and 5.0.
• A menu_single_choice_display_separate question named new_product, that prompts the user for the product to upgrade to. The choices are the same as old_product (above).
4. Create a text object named upgrade_price with text that reads:
   The price for this upgrade is %price%.
5. Run the knowledgebase.

Note, you can use the find() function anywhere any object name is allowed. You do not have to create a fact object to issue a query In this case we needed a separate fact object because the result of query is embedded in a text object.