Simple Demo: OBSERVER execution

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))

DL query ==> Mappings

DL query ==> Multi-repository mappings
Multi-repository mappings ==> several mono-repository mappings

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

Presentation of answer to the user