So what does all this talk about semantic integration really mean? Metadata, image files, meta types? How does semantic rationalization work? This primer explains it all.

Central to the expressor product is the concept of semantic rationalization, the process of mapping fields from multiple and diverse external data resources to data types and definitions that are then used exclusively within expressor projects.

The input to the semantic rationalization process is the metadata describing the data that will be processed and emitted by the expressor application. The output is an image file and entries within the listings of subject areas, terms, term abbreviations, and names comprising the dictionary definitions that will be used in subsequent semantic rationalization efforts.

Image files are specific to the resource for which they were written but different image files will map the same common name — the definition — to differently named fields in their corresponding data resources. For example, the definition part_number may be mapped in two image files to the RDBMS table column name pnum and to the COBOL data item part_no.

The expressor product represents all data as one of five expressor types — byte, datetime, decimal, number, and string. Each definition is associated with an expressor meta type, which is a descriptive alias (e.g., binary or id) for the actual expressor data type (i.e., respectively, byte and string). The meta type assigned to a definition, and its underlying type, may be different from the type assigned to the data in its resource, but this conversion provides for greater consistency and ease of use across projects.

The important concept is that individuals developing expressor data integrations work only with the definition names and their assigned meta types and never need to refer to, or even know, the names or types used by the actual data resources. Consequently, all of the application code and business rule development — referred to as semantic integration — use the definition names and corresponding meta types, thereby providing a decoupling of the integration design from the physical environment.