Simple Metadata Registry

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In metadata the Simple Metadata Registry (SMDR) is a simplified version of the ISO/IEC 11179 metadata registry specification. SMDR uses a single hierarchy of metadata data elements and has explicit URL and XML bindings.

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[edit] Philosophy behind SMDR

SMDR was inspired by the "simplification" movement as demonstrated by applications such as Ruby on Rails and REST where default values take presidency over configuration. SMDR uses standardized URL and file naming conventions to allow for direct URL mapping of data elements and enumerations.

[edit] Structure of SMDR

In SMDR, a data element is one of one of three types:

Conceptual Data Element: A concept or thing used to group properties together. This similar to an Object in Object-Oriented Programming. Concepts can have zero or more sub-concepts but only one superclass.

Property Data Element: A leaf-level data element with a known representation term. This is similar to an Object attribute but without behavior. Representation terms do not necessarily dictate how a data element should be stored in a computer system, but rather the semantic classification of the type of data.

Relationship: A property that relates two data elements together.

SMDR is designed to be simple enough for most data modelers to quickly comprehend but sophisticated enough for most applications.

SMDR is designed to be implemented using simple-readily available software. The base SMDR system could be implemented in MySQL with two base tables (DataElements and Enumerations).

[edit] File system and URL example

Assume a simple structure such as:

  • Thing
    • Activity
      • CourseEnrollment
    • Document
      • ReportCard
  • Organization
    • School
    • SchoolDistrict
  • Person
      • PersonBirthDate
    • Student
      • StateAssignedID
    • Teacher

The following URLs would be relevant:

  VERSIONED_BASENAME/Thing/Person

This returns an XML file of all the data elements associated with the Person concept

Each data element can exist in a path-name in the data element hierarchy:

  VERSIONED_BASENAME/Thing/Person/PersonBirthDate

This returns and XML file that describes all of the properties of the PersonBirthDate data element

  VERSIONED_BASENAME/dd/PersonBirthDate

This returns a list of all the representation terms used in this registry including base and extended terms.

  VERSIONED_BASENAME/Representation_terms

[edit] Extensions to SMDR Base

Although SMDR is designed to be simple, it also is designed to be extensible for specific uses.

The following are examples of extensions of SMDR:

System references - a list of all computer systems that a data element references

Semantic linking - extensions that allow the user to create synonyms between an SMDR and a remote SMDR.

Data source mapping - allows mappings of data elements to data sources such as a relational database or a flat file.