Graph Adapters

To allow for more generic reuse, the mappings used to project data on the semantic graph are designed to be weakly coupled to the type of their source objects.

For this reason, a layer is added between source objects and mappings, in the form of adapters. A graph source adapter is a component implementing an interface (IGraphSourceAdapter), which dictates that the component must have a function receiving an item or a part, together with a dictionary of metadata; and emitting an object (or null) adapted to be plugged into the mapping process.

Currently, the implementation of the adapter layer is limited to the components required by a JSON-based mapper; this is a very general scenario, where any type of object, serialized as JSON, gets mapped into a set of nodes and/or triples. So, this should cover the majority of usage cases.

These adapters have three main tasks:

• serialize the received object into JSON, so that it can be processed by the JSON mapper.
• build the filter used to match the mapping rules to be applied.
• inject some metadata in the received dictionary, extracting them from the source object. Such metadata are typically referenced by mapping rules to do their work. For instance, the item graph adapter extracts from an item its title, and saves it under a constant key. From there, any mapping rule will be able to refer to such metadata.

Thus, whenever a source object enters the mapping process (e.g. because an item or a part has been saved), first the correspondent adapter is used to prepare it, while also providing mappings filter and metadata; once this is done, the mapper can run all the matching mappings, and build the output graph set.