Collection Management

The collection Management Service allows to manipulate collections of complex documents, whose reference model is defined in Content Management.

Reference Model

Document collections are the basic data structure used to organize information inside the Information Organization Services. They are simple unordered sets of complex documents. Each collection is characterized by a collection identifier, labelled with a number of specific properties, and contains a number of documents. Collections can in turn be nested, i.e. a collection can appear as member of another collection. A collection can be static (or materialized), that is contain a statically defined number of objects, that are added to it or deleted from it explicitly, or be virtual. The content of a virtual collection is not determined statically, but rather specified through declarative membership predicates that define which objects currently present in the gCube information-objects space are part of the collection. Its contents are thus determined dynamically at the moment when the collection is accessed by evaluating the membership predicates. For example, it is possible to define the collection of all objects having a certain property value.

Behind the scenes, collections are modeled in terms of the Information-Object model as information objects labelled with the properties of the collections, and to which the members are related via a relationship of type:

contentmanagement:is-member-of

Detailed Service Description

This service provides the high-level operations for collection management, mapping them onto suitable Storage Management operations. The operations provided allow for creating, accessing and destroying collections, modify their properties and their content (e.g. adding or removing members).

Resources and Properties

The service is implemented as a stateless WRSF service. However, it publishes summary information about the collections it manages on the Information System. Each collection is exposed as a distinct gCube-Resource. The properties stored in the resource are the ID and name of the collection, its storage properties (e.g is the collection is virtual and if it is a user-collection), and its references.

Functions

The main functionality supported by the Collection Management Service is shortly described below. Methods are divided into functional groups to ease the reading.

Collection Listing, Creation, Access and Destruction

• listAllCollectionIDsAndNames() – which returns a list of collection ID and collection name representing all the collections currently managed in gCube which are defined in the scope of the caller;
• listAllCollections() – which returns a list of collection descriptions representing all the collection currently managed in gCube which are defined in the scope of the caller;
• listAllCollectionsHavingNames() – which takes as input parameter a message containing a collection name and returns a list of collection descriptions of the collections having such a name. No support for wildcards of similar kind of similarity evaluation. This method and the following one are provided for those services who need to access collections by name instead that by their ID;
• listAllCollectionIDsHavingName() – which takes as input parameter a message containing a collection name and returns a list of collection IDs of the collection having such a name. No support for wildcards of similar kind of similarity evaluation;
• createCollection() – which takes as input parameter a message containing a collection name, a Boolean flag indicating whether the collection is virtual or not, and a membership predicate (optional) returns the Information Object ID of the object created to represent the collection;
• getCollection() – which takes as input parameter a message containing a collection ID and returns the collection description including the object ID, the object type, the object name, the object flavour, the virtual flag, the user collection flag, the membership predicate, the created and last modified value, and the set of other collection properties of the given collection;
• updateCollection() – which takes as input parameter a message containing the collection ID and a membership predicate and changes the collection accordingly. For a virtual collection, this simply updates the stored membership predicate. For a materialized collection, it adds all new members that satisfy the predicate and removes all members that no longer satisfy the predicate. The latter may cause deletion of documents that are no longer member of any collection;
• deleteCollection() – which takes as input parameter a message containing the collection ID and removes such a collection from the set of collections

Member Listing, Addition and Removal

• getMembers() – which takes as input parameter a message containing a collection ID and returns a list of Information Object Description (including the object ID, the object type, the object name, the object flavour, the virtual flag, the user collection flag, the membership predicate, the created and last modified value, and the set of other collection properties) of all the objects members of the given collection;
• getMemberOIDs() – which takes as input parameter a message containing a collection ID and returns a list of Information Object IDs (OIDs) of all the objects members of the given collection;
• getMaterializedCollectionMembership() – which takes as input parameter a message containing a document ID and returns a list of collection IDs and names of the materialized collection such an object is member of;
• addMember() – which takes as input parameter a message containing the collection ID and a Document ID and adds the object to the given collection. This method fails if invoked on a virtual collection;
• removeMember() – which takes as input parameter a message containing a collection ID and a Document ID and removes the specified object from the given collection. This method fails if invoked on a virtual collection;

existing in the gCube system;

Collection Properties Modification

• renameCollection() – which takes as input parameter a message containing a collection ID and a collection name and assigns the specified name to the given collection;
• setCollectionProperty() – which takes as input parameter a message containing a collection ID, a property name, a property type and a property value and attach such a property to the given collection;
• getCollectionProperty() – which takes as input parameter a message containing a collection ID and a property name and returns the specified collection property, i.e. the object ID, the property name, type and value;
• unsetCollectionProperty() – which takes as input parameter a message containing a collection ID and a property name and removes the specified parameter from the ones attached to the given collection;
• isUserCollection() – which takes as input parameter a message containing the collection ID and returns a Boolean value indicating whether the given collection is a user collection, i.e. can be directly perceived by the VRE users, or not;
• setUserCollection() – which takes as input parameter a message containing a collection ID and a Boolean value indicating whether the specified collection has to be considered a user collection, i.e. a collection that is perceived by the users of some Virtual Research Environment, or not and sets such a property on the given collection;