Databases Reference
In-Depth Information
.
If the session contains information that is no longer valid. This could be the case
when calculated members or calculated cells are created in the cube by the user, and
the cube has undergone serious structural changes. For example, a structural change
such as the deletion of a dimension used in the calculation stored in the session
would trigger termination of the session.
XML/A Methods
XML/A defines two methods:
Discover
, which retrieves metadata from the server; and
Execute
, which causes the server to perform some command.
The
Discover
Method
The
Discover
method enables the client application to read metadata that contains neces-
sary information about the XML/A provider. For example, that metadata might contain a
list of accessible sources of data, a list of properties supported by the XML/A provider, the
keywords that the provider recognizes, or a list of all the databases accessible to the client.
The following is the signature for the
Discover
method:
Discover (in RequestType as EnumString,
in Restrictions as Array,
in Propertiesas Array,
out Resultset as Rowset)
The result of a
Discover
request is an XML document in
Rowset
format. The
Discover
method supports the following parameters.
RequestType
Use the
RequestType
parameter to specify the information returned by the
Discover
method.
The XML/A specification defines six
Discover
request types. (See the XML/A specification
for a complete list of request types.) In addition, the XML/A provider supports all schema
rowsets defined by the OLE DB for OLAP and the OLE DB for data-mining specifications.
Analysis Services defines additional provider-specific
Discover
request types.
This parameter is very similar to its counterpart in OLE DB, but there are some differences.
For the OLE DB method
GetSchemaRowset
, the
RequestType
is of data type GUID; for
XML/A, it is a string that contains the name of the request type rather than its GUID.
Restrictions
Use the
Restrictions
parameter to limit the information returned by
Discover
. You can
construct a collection of restrictions and pass it to the server in an XML/A request.
With the
Restrictions
parameter in OLE DB, the list of restrictions is indexed; in XML/A,
you can use keywords to list the restrictions in any order. This greater flexibility can
simplify the creation of requests.
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