Simple Demo: OBSERVER execution

1. Query Edition Retrieve the name, location and room rate for hotels with a room rate equals to $200

   [Name Location Price] of (AND hotel (FILLS Price 200))

2. DL query ==> Mappings
   • DL query ==> Multi-repository mappings
   • Multi-repository mappings ==> several mono-repository mappings
3. Access to data repositories
   • Mono-repository mappings ==> queries in Local Query Language (LQL)
   • Execution of LQL queries
     • Access data using wrappers
     • Applying transformer functions
   • Obtaining final answer using an auxiliar database

     SELECT ALIAS7.name, ALIAS7.location, ALIAS6.price
     FROM
         (
         SELECT name, price
         FROM AUX-1
         UNION
         SELECT name, price
         FROM AUX-2
         UNION
         SELECT name, price
         FROM AUX-3
         )ALIAS6,
         (
         SELECT ALIAS5.name, ALIAS4.location
         FROM
             (
             SELECT name, location
             FROM AUX-4
             UNION
             SELECT name, location
             FROM AUX-5
             UNION
             SELECT name, location
             FROM AUX-6
             ) ALIAS4,
             (
             SELECT name
             FROM 
                 (
                 SELECT name
                 FROM AUX-7
                 UNION
                 SELECT name
                 FROM AUX-8
                 UNION
                 SELECT name
                 FROM AUX-9
                 ) ALIAS2,
                 (
                 SELECT name
                 FROM
                     (
                     SELECT name
                     FROM AUX-10
                     UNION
                     SELECT name
                     FROM AUX-11
                     UNION
                     SELECT name
                     FROM AUX-12
                     ) ALIAS0,
                     (
                     SELECT name
                     FROM AUX-10 WHERE price = 200
                     UNION
                     SELECT name
                     FROM AUX-11 WHERE price = 200
                     UNION
                     SELECT name
                     FROM AUX-12 WHERE price = 200
                     ) ALIAS1
                 WHERE ALIAS0.name = ALIAS1.name
                 ) ALIAS3
             WHERE ALIAS2.name = ALIAS3.name
             ) ALIAS5
         WHERE ALIAS4.name = ALIAS5.name
         )ALIAS7
     WHERE ALIAS6.name = ALIAS7.name
         
     

4. Presentation of answer to the user