Make reconciliation score optional (#133)

* Make reconciliation score optional

Closes #127.

* Add more notes about optional scoring

* Improve explanation on optional score

Co-authored-by: Fabian Steeg <steeg@hbz-nrw.de>

---------

Co-authored-by: Fabian Steeg <steeg@hbz-nrw.de>

draft/examples/reconciliation-result-batch/valid/minimal.json

@@ -0,0 +1,28 @@
+{
+  "results": [
+    {
+      "candidates": [
+        {
+          "id": "120333937",
+          "name": "Urbaniak, Regina"
+        },
+        {
+          "id": "1127147390",
+          "name": "Urbaniak, Jan"
+        }
+      ]
+    },
+    {
+      "candidates": [
+        {
+          "id": "123064325",
+          "name": "Schwanhold, Ernst"
+        },
+        {
+          "id": "116362988X",
+          "name": "Schwanhold, Nadine"
+        }
+      ]
+    }
+  ]
+}

draft/index.html

@@ -571,7 +571,7 @@ <h3>Reconciliation Query Responses</h3>
 	    <dt><code>type</code></dt>
 	    <dd>The types of the candidate entity;</dd>
 	    <dt><code>score</code></dt>
-	    <dd>A numeral indicating how well this candidate entity matches the query: a higher score indicates a better match;</dt>
+	    <dd>An optional numeral indicating how well this candidate entity matches the query: a higher score indicates a better match. If candidates are scored, the reconciliation service SHOULD sort candidates in decreasing score order;</dt>
             <dt><code>features</code></dt>
             <dd>An optional array of <a>matching features</a>;</dd>
 	    <dt><code>match</code></dt>
@@ -598,7 +598,7 @@ <h3>Reconciliation Query Responses</h3>
         </p>
         <p>
 	  A <dfn>reconciliation result</dfn> is a set of <a>reconciliation candidates</a>. It is serialized in JSON
-	  as an object containing in the field <code>candidates</code> an array of such reconciliation candidate objects. This array SHOULD be sorted by decreasing score.
+	  as an object containing in the field <code>candidates</code> an array of such reconciliation candidate objects.
         </p>
         <p>
           A <dfn>reconciliation result batch</dfn> is an array of <a>reconciliation results</a> given in the same order as in the corresponding <a>reconciliation query batch</a>.
@@ -644,6 +644,7 @@ <h3>A Note on Candidate Retrieval and Scoring</h3>
 	</p>
 	<p>
 	  Deciding on a scoring method is one of the main difficulties in developing a reconciliation service.
+          Depending on the use case, we might not want a score at all: in cases like geo containment (a place should be inside a specific area) or date ranges (a point in time should be inside a specific time range) the score is irrelevant, as candidates are either in or out. Thus the score attribute is optional.
           Services are encouraged to expose as many <a>matching features</a> as they deem useful, in particular
           features which require knowledge of global statistics on the database or other attributes. Examples include:
           <dl>

draft/schemas/reconciliation-result-batch.json

@@ -101,8 +101,7 @@
               },
               "required": [
                 "id",
-                "name",
-                "score"
+                "name"
               ]
             }
           }