After the user submits a query, the query decomposition module in accordance with the above rules to check the validity of the request, the grammar check.
Check is successful, has begun to decompose. Query Decomposition in accordance with the following principles:
1> independent inquiry to split: the middleware necessary to connect the unit, the query is decomposed into a set of sub-queries, each group of sub-queries corresponding to a single data source.
2> in accordance with relevant multi-database query split: two middleware data needs to match the query first decomposed into a single middleware on which the independent sub-queries, check out the results of the independent sub-data generation to another middleware data matching subquery in order to achieve the connection of two middleware data need to match the query.
Decomposition examples:
DEFINE [server1.db1.table1 = a] [server2.db2.table2 = b] [server3.db3.table3 = c]
SELECT [a. *] [b. *]
FROM [a] [b]
WHERE [a.begintime>''2004-9-8''] [a.id> c.id] [a.id = b.id] ADDITION [a.di = DISTINCT]
Decomposition based on the principle of decomposition is as follows:
1> Decomposition of the independent sub-queries, and recorded as a new query module variables
DEFINE [SELECT [a. *] FROM [a] WHERE [a.begintime>''2004-9-8'']
ADDITION [a.di = DISTINCT] = d]
2> in a separate sub-query multiple database queries based on the split, each query is recorded as a new query module variables
DEFINE [SELECT [d. *] FROM [d] WHERE [d.id> c.id] = e]
DEFINE [SELECT [e. *] [b. *] FROM [e] [b] WHERE [e.id = b.id] = f]
Query end, f record query results.
3.2 Application Description
Domestic airlines have developed their own aviation information systems, WEB-based services for heterogeneous database integration middleware integrated major airlines to provide users with data query service. Described as follows:
1> flight, China Eastern, China Southern Airlines, Sichuan Airlines to install integration middleware, respectively, for local configuration, are connected to its own aeronautical information database, and configuration and connection to other integrated middleware, so as to constitute an aviation information sharing network.
2> Client middleware through which any of the services provided by WEB interface to submit queries, query through decomposition, routing to network with other middleware, the implementation of the final results returned to the client.
Query example: user queries 2004-9-7 sent from Beijing, Sichuan and Hainan flight, and arrival time of flights starting from Sichuan than the earlier flight departing from Hainan
Agreed to submit the query the user as follows:
Define [server1.db1.info = a] [server2.db2.infomation = b]
Select [a. *] [b. *] from [a] [b]
Where [a.destination = Beijing] And [a.begintime = 2004-9-7]
And [b.destination = Beijing] And [b.begintime = 2004-9-7]
And [a.endtime
Description: server1.db1.info = a Sichuan Airlines middleware, the data connected
server2.db2.infomation = b Southern middleware connected to the data
The query is decomposed into
1> Define [Select a. * from [server1.db1.info = a]
Where [a.destination = Beijing] And [a.begintime = 2004-9-7]
= C]
2> Define [Select b. * from [server2.db2.info = b]
Where [b.destination = Beijing] And [b.begintime = 2004-9-7]
= D]
3> take 1 data and 2 data sub-query matching
Select [c. *] [d. *] from [c] [d] where [c.endtime
Constituted by the middleware data sharing network has high flexibility, other airlines only need to install the integration middleware, configuration, and shared network connection can easily expand the data-sharing network.
4 Conclusion
Data Integration for the realization of EAI, for enterprise internal integration of great importance to this paper, a WEB-based services, middleware, heterogeneous database integration solutions. The middleware solution is certainly feasible, and practical, capable of heterogeneous database integration.