The Annotation Back-End Service Sample Clauses

The Annotation Back-End Service. The design of the service is distributed across three port-types: the Manager, the Broker, and the Factory port-types. The Manager port-type manages annotations of objects within a single target collection, and thus across all the annotation collections for it. Clients may create annotation collections for the target collection, and then add, update, retrieve or delete annotation from them. These operations map directly onto equivalent operations of the Metadata Management service and are offered here mostly to present a single point of contact for annotations. Clients may also retrieve annotations across multiple annotation collections, though of course no write operation is offered at this level of abstraction. All operations process and produce bulk data to avoid the latency of finer-grained interactions. Similarly, all operations are conceptually overloaded to work either by-value – inputs and outputs are entirely included in message payloads – or else by-reference – input and outputs are throttled in ‘pages’ using the resultset abstractions (cf. Section 7.2). Finally, all operations are tolerant to fine-grained failures, through they record them and then report them as return values. Overall, the port-type is the main point of contact for clients that operate within the scope of a single collection C, e.g. wish to present annotations for its objects regardless of the annotation collections in which they are hosted, or else wish to focus their interactions on individual annotation collections. The Manager port-type is stateful, in that it maintains – both in memory and on the file system – summary information about the annotation collections of the target collections. The information is grouped under local ‘proxies’ of the target collections, and the proxies are bound to the port-type interface on a per-request basis, in line with the implied resource pattern of WSRF. In particular, the pairing of the Manager interface and collection proxies identifies WS-Resources informally referred to as Managers. Managers are created in response to client requests to the Factory port-type and inherit their scope. It is within this scope that – at creation time – a selection of their state is published in the Information System (cf. Section 5.2). In WSRF terminology, these are the Resource Properties that identify the target collections and their annotation collections and by which Managers can be discovered by ▇▇▇ clients. Following publication, Managers are kept u...