From the post:
The Esri Data Interoperability Extension gives GIS professionals the ability to build complex spatial extraction, transformation, and loading (ETL) tools. Traditionally the crosswalking of feature classes and attributes is done prior to setting up the migration tools and is used only as a guide. The drawback to this method is that it takes a considerable amount of time to build the crosswalks and then to build the ETL tools.
GISI’s article, “Building Attribute and Value Crosswalks in ESRI Data Interoperability Extension the Scalable/Dynamic Way” outlines the use of the SchemaMapper transformer within Data Interoperability Extension which can pull crosswalk information directly from properly formatted tables. For large projects this means you can store crosswalk information in a single repository and point each ETL tool to that repository without needing to manage multiple crosswalk documents. For projects that might change during the lifecycle of the project the use of SchemaMapper means that changes can be made to the repository without requiring any additional changes to the ETL tool. There are three examples used in this article which encompasses a majority of crosswalking tasks; feature class to feature class, attribute to attribute, and attribute value to attribute value crosswalking. All of the examples use CSV files to store the crosswalk information; however the transformer can pull directly from RDBMS tables as well which gives you the ability to build a user interface to create and update crosswalks which is recommended for large scale projects.
If you have time, please read the original article. Obtain it from the links listed in the final paragraph.
I need for you to verify my reading of the process described in that article.
As far as I can tell, the author never say “why” or on what basis the various mappings are being made.
I would be hard pressed to duplicate the mapping based on the information given about the original data sources.
Having an opaque mapping can be useful, as the article says but what if I stumble upon the mapping five years from now? Or two years? Or perhaps even six months from now?
Specifying the “why” of a mapping is something topic maps are uniquely qualified to do.
You can define merging rules that require the basis for mapping to be specified.
If that basis is absent, no merging occurs.