In metadata

Metadata

The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

 the Simple Metadata Registry (SMDR) is a simplified version of the ISO/IEC 11179

ISO/IEC 11179

ISO/IEC 11179 is an international standard for representing metadata for an organization in a metadata registry.- Intended purpose :...

 metadata registry specification. SMDR uses a REST

Rest

Rest may refer to:* Leisure* Human relaxation* SleepRest may also refer to:* Rest , a pause in a piece of music* Rest , the relation between two observers* Rest , a 2008 album by Gregor Samsa...

 interface to create a unique URI

Úri

Úriis a village and commune in the comitatus of Pest in Hungary....

 for each data element in a metadata registry.

Philosophy behind SMDR

SMDR was inspired by the "simplification" movement as demonstrated by applications such as Ruby on Rails

Ruby on Rails

Ruby on Rails, often shortened to Rails or RoR, is an open source web application framework for the Ruby programming language.-History:...

 and REST

Representational State Transfer

Representational state transfer is a style of software architecture for distributed hypermedia systems such as the World Wide Web. The term representational state transfer was introduced and defined in 2000 by Roy Fielding in his doctoral dissertation...

 where default values take precedence over configuration. SMDR uses standardized URL and file naming conventions to allow for direct URL mapping of data element

Data element

In metadata, the term data element is an atomic unit of data that has precise meaning or precise semantics. A data element has:# An identification such as a data element name# A clear data element definition# One or more representation terms...

s and enumerations.

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

Object-oriented programming

Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...

. 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

Representation term

A representation term is a word, or a combination of words, that semantically represent the data type of a data element. A representation term is commonly referred to as a class word by those familiar with data dictionaries...

. 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).

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. You can also
access a flat version of all data elements using the data element construct.
VERSIONED_BASENAME/data-element/PersonBirthDate

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

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.