Information Object Model Clause Samples

Information Object Model. The elementary constructs of the model are information-objects (a node of the graph) and object references (the arcs). The ER Diagram in Figure 20 describes the model. • An Information Object (IO) represents an elementary information unity. It is uniquely identified by an Object Identifier (OID), is labelled with a name6 and a type7 and Information optionally annotated with a number of properties. These properties are simple key-type-value associations. Finally, it can be associated with a raw-content. The raw content of an object is content of any kind. The model hides the actual storage details of the content of an object, that can be for instance stored as a file in gLite or as BLOB-field in a database, or maintained in storage facilities not under direct control of the Information Organization Services, e.g. as file stored in a remote server and accessible through some protocol like http, ftp or gridftp. • An object reference “links” two Information Objects. Each object might (i) reference many other objects and (ii) be referenced by many objects (m-n relationship). A reference is directed, it is labelled with a type attribute, called primary role, a secondary role, that may optionally further specify the function of the primary role8, 6 The name is a plain string that can be attached to an Information Object for ease of identification. It may be employed to additionally equip Information Objects with non-unique, yet human-interpretable names, and can be empty. 7 The type identifies the kind of Information Object, like document, collection, aggregate, metadata, external document etc. It is a mandatory attribute.