MetaSchema

MetaSchema is a Data Definition Language specification.

Design goals

Schemata must

• Be language/platform agnostic
• Allow re-use and composition

Key elements/concepts

• Physical Datatype
• Logical Datatype
• Storage Engine
• Presentation Widget
• Validator
• Entity
• Attribute
• Scenario

Physical Datatype

Physical Datatypes are primitive datatypes supported by:

• Programming Languages, eg. Java, PHP, Javascript, etc.
• Database Systems (relational, object oriented, NoSQL, etc)
• Data Exchange Formats, eg. JSON, XML, etc.

List of Physical Datatypes:

• Char
• String
• Integer
• Double
• Boolean
• Date
• Datetime
• Time

Datatypes in database systems:

• MySQL Datatypes - http://dev.mysql.com/doc/refman/5.0/en/data-types.html
• Sql Server Data Types - http://msdn.microsoft.com/en-us/library/ms187752.aspx

Datatypes in programming languages:

• Java Primitive Datatypes - http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html
• PHP Types - http://www.php.net/manual/en/language.types.php
• Javascript Datatypes - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures

Datatypes in data exchange formats:

• JSON Datatypes - http://en.wikipedia.org/wiki/JSON#Data_types.2C_syntax_and_example

References:

• Data types - http://en.wikipedia.org/wiki/Data_type

Composite Datatype

Composite datatypes allow the construction of logical datatypes

• Vector2: Can be used in ranges, vectors, etc.
• Vector3: same as above

Logical Datatype

Logical data types introduce semantics. They must define representations using primitive data types.

Here's a list of some logical data types:

Color

Representations:

• String Datatype with hex "#RRGGBB" format
• String Datatype with decimal "(R, G, B)" format

Date

Representations:

• String Datatype with "Y-m-d" format

Datetime

Representations:

• String Datatype with "Y-m-d H:i:s" format

Time

Representations:

• String Datatype with "H:i:s" format

Collection

The following collections are allowed:

• List - ordered list of items
• Set - unordered list of unique items
• Map - lookup tables using strings as keys

References:

• http://en.wikipedia.org/wiki/Collection_(abstract_data_type)

Validator

A validator is applied against a primitive datatype to enforce semantics.

Example validators:

• MinValue: Works on Integer and Double datatype

References

• Entity–attribute–value model - http://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model
• Generic data model - http://en.wikipedia.org/wiki/Generic_data_model
• Three schema approach - http://en.wikipedia.org/wiki/Three_schema_approach
• Putting Semi-structured Data to Practice - homes.cs.washington.edu/~alon/cikm98.ppt‎
• The GMAP: a versatile tool for physical data independence - http://www.vldb.org/journal/VLDBJ5/60050101.pdf