Defining Data Sources and Wrappers¶
A wrapper must be created and assigned to a base relation in order to be able to obtain data from a specific source. Each wrapper should provide access to the data forming a base relation in a source, so that they are structured in a manner similar to a Relational Database table with regard to the Virtual DataPort server. More specifically, each wrapper should provide an overall view of the source according to the base relation model provided in the previous section.
The process of generating wrappers for source types such as JDBC/ODBC Databases, SOAP and REST Web Services, LDAP servers, XML documents, delimited text files or unstructured information indices may be undertaken quickly and simply with the help of the Denodo Virtual DataPort administration tool. It is normally necessary to previously create a data source for the source that will encapsulate data to access it that is reusable by the different wrappers acting on it.
Wrappers can be created for semi-structured Web sources (WWW) in a fully graphic manner with Denodo ITPilot. It is also possible to create wrappers for specific applications using the CUSTOM wrapper type.
Should you wish to create data sources and wrappers directly using VQL, without the help of the administration tool, section Generating Wrappers and Data Sources of this document describes how to do so. In general, use of the administration tool is strongly recommended for these tasks, as the process is much simpler and automatic.
Once the wrapper has been created for a source, all that needs to be done is link it to the adequate search method or methods from the base relation that represents said data in the system (see section Creating a Base View). You can now make queries on the base relation.