Add top level method: get_relation(....) ?

[B-Stefan]

Currently the ProvDb class expose methods like get_element(identifier) this method returns 3 possible types:

• ProvAgent
• ProvEntity
• ProvActivity

In order to provide a consistent we should discuss the advantage of a method like get_relation()
For example:

matching_attributes = dict()
matching_attributes.update({'prov:type': 'prov:Mention'})
pro_relation = prov_api.get_relation(matching_attributes)

The problem is that this kind of filter mechanism could return a list instead of a single entry. According to the PROV spec the uniques of a relation is defined by all formal attributes (eg form / to node). Maybe we can set a filter by this formal attributes.

This seems the best solution but also require to alter the BaseAdapter and all adapter implementations.

Also I really don't know if it is necessary to get only a single relation between to ProvElements. Is there any good use case for this?

[Drake81]

If we implement a method like prov_api.get_relation(matching_attributes) we should return list in every case, since its easier to process.

I don't think just return the relation itself is interesting.
At least it should return a list of all relations, including the involved node as well.
i.e.

[
 {
  id:{ 
    type:prov-type,
    attributes: ..
  },
  id:{
   type: prov-type,
   attributes: ...
  },
 },
 {...} # next entry
]

But, usually it question would be like: "Which entities were in created in a particular process".
Isn't there a filter function that could solve such questions?