OsidObject is the top level interface for all OSID Objects. An OsidObject is an object identified by an OSID Id and may implement optional interfaces. OsidObjects also contain a display name and a description. These fields are required but may be used for a variety of purposes ranging from a primary name and description of the OsidObject to a more user friendly display of various attributes.

Creation of OsidObjects and the modification of their data is managed through the associated OsidSession. The OsidManager is used to create the appropriate OsidSession for OsidObject creation, updates and deletes.

All OsidObjects are identified by an immutable Id. An Id is assigned to an object upon creation of the object and cannot be changed once assigned.

An OsidObject may support one or more supplementary records which are expressed in the form of interfaces. Each record interface is identified by a Type. A record interface may extend another record interface where support of the parent record interface is implied. In this case of interface inheritance, support of the parent record type may be implied through hasRecordType() and not explicit in getRecordTypes().

For example, if recordB extends recordA, typeB is a child of typeA. If a record implements typeB, than it also implements typeA. An application that only knows about typeA retrieves recordA. An application that knows about typeB, retrieves recordB which is the union of methods specified in typeA and typeB. If an application requests typeA, it may not attempt to access methods defined in typeB as they may not exist until explicitly requested. The mechanics of this polymorphism is defined by the language binder. One mechanism might be the use of casting.

In addition to the OsidRecord Types, OsidObjects also have a genus Type. A genus Type indicates a classification or kind of the object where an "is a" relationship exists. The purpose of of the genus Type is to avoid the creation of unnecessary record types that may needlessly complicate an interface hierarchy or introduce interoperability issues. For example, an OsidObject may have a OsidRecord Type of Publication that defines methods pertinent to publications, such as an ISBN number. An OSID Provider may wish to distinguish between books and journals without having the need of new record interfaces. In this case, the genus Type may be one of Book or Journal.While this distinction can aid a search, these genres should be treated in such a way that do not introduce interoperability problems.

Like OsidRecord Types, the genus Types may also exist in an implicit type hierarchy. An OsidObject always has at least one genus Type. Genus types should not be confused with subject tagging, which is managed in the Ontology OSID. Unlike OsidRecord Types, an OsidObject genus Type may be modified. However, once an OsidObject is created with a record Type, it cannot be changed.

Methods that return values are not permitted to return null. If a value is not set, it is indicated in the Metadata of the update OsidObjectForm.