Add projections schema to start doc

docs/source/data-model.rst

@@ -139,6 +139,14 @@ A typical example
     Time is given in UNIX time (seconds since 1970). Software for looking at
     the data would, of course, translate that into a more human-readable form.
 
+Projections (Experimental):
+
+The run_start metadata can include a projections field.
+It is intended that a projection is an aid to interacting with external systems using standardized vocabularies.
+Projections might be used in a variety of use cases such as providing run data to analysis tools or suitcases.
+Each projection represents multiple ways to represent data from the run. Each field in the projection dictionary 
+is an unique and externally-identifiable string and each value is an instruction for accessing dat from the run. 
+
 The run start document formal schema:
 
 .. literalinclude:: ../../event_model/schemas/run_start.json

event_model/schemas/run_start.json

@@ -4,6 +4,42 @@
             "title" : "data_type",
             "patternProperties": {"^([^./]+)$": {"$ref": "#/definitions/data_type"}},
             "additionalProperties": false
+        },
+        "projection": {
+            "description": "Where to get the data from",
+            "type": "object",
+            "properties" : {
+                "type": {"type": "string", "enum": ["linked", "calculated", "static"], "description": "linked: a value linked from the data set, calculated: a value that requires calculation, static:  a value defined here in the projection "},
+                "stream": {"type": "string"},
+                "location": {"enum" : ["event", "configuration"], "description": "event comes from event, configuration comes from fields inthe run_start document"},
+                "field": {"type": "string"},
+                "calculation": {
+                    "title" : "calculation properties",
+                    "properties": {
+                        "callable": {"type": "string", "description": "callable function to perform calculation"},
+                        "args": {"type": "array", "decription": "args for calculation callable"},
+                        "kwargs": {"type": "object", "description": "kwargs for calcalation callable"}
+                    },
+                    "required": ["callable"]
+                }
+            },
+            "required" : ["type"],
+            "additionalProperties": false
+        },
+        "projections": {
+            "title" : "Describe how to interperet this run as the given projection",
+            "properties":{
+                "name": {"type": "string", "description": "The name of the projection"},
+                "version": {"type": "string", "description": "The version of the projection spec. Can specify the version of an external specification."},
+                "configuration" : {"type": "object", "description": "Static information about projection"},
+                "projection" : {
+                    "type": "object",
+                    "patternProperties": {".": {"$ref": "#/definitions/projection"}},
+                    "additionalProperties": false
+                }
+            },
+            "additionalProperties":  false,
+            "required" : ["projection", "version", "configuration"]
         }
     },
     "properties": {
@@ -35,6 +71,10 @@
             "type": "string",
             "description": "Unix owner to associate this data with"
         },
+        "projections": {
+            "type": "array",
+            "items": {"$ref": "#/definitions/projections"}
+        },
         "hints": {
             "type": "object",
             "description": "Start-level hints",

event_model/tests/test_projections.py

@@ -0,0 +1,62 @@
+import event_model
+import pytest
+from jsonschema.exceptions import ValidationError
+
+
+def test_projection_start_doc():
+    run_bundle = event_model.compose_run(uid="42", metadata={"projections": valid_projections})
+    start_doc = run_bundle.start_doc
+    assert start_doc['projections'] == valid_projections
+
+
+def test_projection_schema():
+    start_doc['projections'] = valid_projections
+    event_model.schema_validators[event_model.DocumentNames.start].validate(start_doc)
+
+    with pytest.raises(ValidationError):
+        start_doc['projections'] = invalid_projections
+        event_model.schema_validators[event_model.DocumentNames.start].validate(start_doc)
+
+
+valid_projections = [
+            {
+                "name": "test",
+                "version": "42.0.0",
+                "configuration": {},
+                "projection": {
+                    'entry/instrument/detector/data': {
+                        'type': 'linked',
+                        'location': 'event',
+                        'stream': 'primary',
+                        'field': 'ccd',
+                    },
+                    '/entry/instrument/wavelength': {
+                        'type': 'calculated',
+                        'calculation': {
+                            'callable': 'pizza.order:slice',
+                            'kwargs': {'toppings': 'cheese'}
+                        }
+                    }
+                },
+            }
+        ]
+
+invalid_projections = [
+                {
+                    "name": "test",
+                    "version": "42.0.0",
+                    "configuration": {},
+                    "projection": {
+                        'entry/instrument/detector/data': {
+                            'location': 'THIS IS NOT VALID',
+                            'stream': 'primary',
+                            'field': 'ccd',
+                        },
+                    },
+                }
+            ]
+
+start_doc = {
+    "uid": "abc",
+    "time": 0,
+}