MetadataDrivenAction

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Definition: 

MetadataDrivenActions are Acts in which their logic is defined by validation and transformation rules expressed in some standard rule language.

Explanatory Notes: 

Whereas ComputationActions are used in statistical packages like SPSS, Stata, SAS and R to perform data management and data transformations, MetadataDrivenActions are used by data pipelines, e.g. ETL (Extract Transform Load) platforms, along with ComputationActions.

In a data pipeline the user is presented with a menu of MetadataDrivenActions that are captured here in an external controlled vocabulary. Users enter into a dialog with the platform through which they customize the MetadataDrivenAction. The user writes no code. The dialog is saved.

In the course of this dialog the user might specify a data source, specify which variables to keep or drop, rename variables, specify join specifics, create a value map between two variables and so forth.

MetadataDrivenActions represent this dialog in some standard rule language, e.g. Structured Data Transformation Language (SDTL) , Validation and Transformation Language (VTL), etc.. In fact, MetaDataDrivenAction can use VTL with certain "extensions". Together they form quasi-VTL. quasi-VTL in turn conforms to a known schema. Using this schema users can render the quasi-VTL as XHTML and record it in the MetadataDrivenAction quasiVTL property. quasiVTL supports structured text.

Note that we would like NOT to create specific subtypes of MetadataDrivenAction -- one for each transformation. In fact there are a dozen or more such actions that will be captured in the MetadataDrivenAction types external controlled vocabulary. As an alternative, users can optionally write structured text based on a known schema. In this approach we are able to "evolve" SDTL as needed without changing our model. Instead, as our language "evolves", we one have to update its schema.

Example: 
Some data management systems present users with a menu of actions they can use in a sequence to perform a specific task. The system engages the user in a dialog driven by an action template. The dialog completes the template which the system then uses to perform the action. The user doesn't write any code.
Property: 
NameCardinalityDatatypeDescription
activityDescription
0..1
Describes the transformation activity
typeOfMetadataDrivenAction
0..1
Allows for the specification of a transformation type supporting the use of an external controlled vocabulary
quasiVTL
0..1
A definition of the action in XHTML that conforms to the quasi-VTL schema. Each action has its own definition that a user optionally completes.
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