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UDB DataSourceMetaContainer object

Patrick Camphuijsen

This article is about the DataSourceMetaContainer object in the UDB object model. This model is for data exchange between USoft web UIs and Rules Engines.

This model is built around the udb, DataSourceMetaContainer, DataSourceContainer, Rowset, Rows, ColsMeta, and Cols object types. See also UDB events.

A DataSourceMetaContainer object has knowledge of metadata that describe a data source or set of data sources.

Data source selectors

In the syntax block below, the required ds is a data source selector: an expression whereby you identify a single data source or multiple data source. Data source selectors play a role in calls to the DataSourceMetaContainer object, but also in calls to the DataSourceContainer object:

$.udbMeta( ds )
$.udb( ds )

You can identify a single data source by a simple data-source name string. You can identify a set of multiple data sources by an array of simple string values.

If the data source is on the current page, you can identify it simply either by its data-source-name or by its data-source-id. if it is on a different page, you can identify it by prefixing page-id followed by a period. It is also possible to refer to a data source in a specific frame control. Prefix with frame-id followed by a double colon, or to identify the top-level frame, write the double colon but not the frame-id prefix.

You can also identify a data source using data source path syntax.

Finally, you can select types of data source by using meta-selector values. This selection technique cannot be combined with the other options. The ‘:table’ meta-selector selects all table data sources in scope. The ':variable’ meta-selector selects all variable data sources in scope. The ':virtual’ meta-selector selects all virtual data sources in scope.

Examples

var dsc = $.udbMeta('EMP');
var dsc = $.udb('EMP');
var dsc = $.udbMeta(['EMP','DEPT']);
var dsc = $.udb(['EMP','DEPT']);
var dsc = $.udbMeta('DS57');
var dsc = $.udb('DS57');
var dsc = $.udbMeta('ApplicationFrame::DS57');
var dsc = $.udb('ApplicationFrame::DS57');
var dsc = $.udbMeta(':table');
var dsc = $.udb(':table');

Syntax

$.udbMeta( ds )

ds                 ::= { data-source | data-source-array )

data-source-array  ::= [ data-source, data-source ... ]

data-source  ::=
    {
      [page-id.][[frame-id]::]{data-source-name|data-source-id} |
data-source-path  |
meta-selector
    }

meta-selector ::=   
    {
      :table    |
      :variable |
      :virtual
    }

In this syntax block, square brackets are ambiguous. They are used as literal array brackets when explaining data-source-array in the second line. In the other cases, they surround optional, as opposed to required, syntax elements.

The required ds is a data source selector as explained at the top of this article.
 

All functions listed for the udbMeta are equally exposed by the udb object.

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