Summary

Interfaces, contracts, methods, operations, entities, objects, and tables, oh my! The OSID Specification defines its own language solely in reference to itself. Developers will look at it from the OSID Language Binding perspective. Others will import concepts from what they have worked with in databases, web services, or MVC-based platforms. The result is a mash of terms that matters once in a while.

The OSID Perspective

You can look at the OSID Specification schema for its specification terminology. It defines:

• osid: a bunch of interfaces an enumerations
• enumeration: a list of values
• interface: a bunch of method definitions
• method: something that is invoked with parameters, returns a value or an error
• parameter: defines what may be supplied to a method as an argument, can be an interface, enumeration, or a language primitive
• return: defines what may be returned from a method, if anything, can be an interface, enumeration, or a language primitive
• language primitive: boolean, byte, cardinal. decimal integer, object. string, timestamp
• error: an error from a method such as OPERATION_FAILED or ILLEGAL_STATE
• compliance: a compliance statement for a method - mandatory or optional

The Java Perspective

• package: a bunch of interfaces, classes, enums, annotations, and other sub-packages
• enums: constants and methods
• interface: a bunch of method definitions
• class: a pile of attributes that include methods and may implement one or more interfaces
• object: an instance of a single class
• method: something that is invoked with parameters, returns a value or throws an exception
• parameter: defines the type supplied to a method as an argument, can be a class, interface, enum, or a primitive
• return: defines the type of return value, can be a class, interface, enum, primitive, or void
• primitive: boolean, byte, char, double, float, int, long, short
• exception: an event that occurs during the execution of a program that disrupts the normal flow of instructions such as SecurityException or NullPointerException 

The OSID Specification is transformed into the OSID Java Binding. The resulting merge creates the following OSID terminology in Java:

• osid: a Java packages and its sub-packages
• package: a bunch of interfaces and enums
• enums: constants and methods
• interface: a bunch of method definitions
• method: something that is invoked with parameters, returns a value or throws an exception
• parameter: defines the type supplied to a method as an argument, can be an interface, enum, or a primitive
• return: defines the type of return value, can be an interface, enum, primitive, or void
• primitive: boolean, byte, or long
• exception: an error from a method such as such as OperationFailedException or IllegalStateException 

Concepts like classes and objects disappear. Others like parameter and primitive have a narrower connotation than what a Java developer would be accustomed. And the definition of "osid" gets fuzzier.

Terminology Issues

 Attributes & Data Fields

Service entities, such as OsidObjects, are expressed using interfaces.  What is presented to an OSID Consumer is the means for accessing information at that point in time. OSID Providers can provide real time information through its methods.

An OSID Provider may likely employ data objects to satisfy the contract of an OsidObject. An OSID Consumer sees this through the window of the interface. The OSID Consumer may do whatever it likes with this information, including referring to them as simple data elements. However it can be an impediment when trying to understand the nature and applications of these interfaces whose implementation may require an underlying OSID Provider rather than a pull from a database table, for example.

 Boundary

 Contract

The term contract is often used in service designs to distinguish an interface from a message structure or DTO. The message structure and DTO are considered data while the contract defines the operations on that data. OSIDs define the contractual agreement between service consumers and service providers. In the OSID world, everything in the specification can be considered a contract. This term doesn't help qualify anything here but is often used to emphasize the nature of the interface.

 DTO

A Data Transfer Object is used to transfer bags of data through system layers. However, OSIDs are just piles of method signatures organized in interfaces.  

 Endpoint

 Entity

 Message Structure

 Operations

 Relation

 Service

The term "service" doesn't have any formal definition in the OSID Specification. It's tossed around because this is a Service Design Methodology. 

 Standard