--- /dev/null
+// Copyright 2018 Google LLC.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+syntax = "proto3";
+
+package google.api.expr.v1alpha1;
+
+import "google/api/expr/v1alpha1/value.proto";
+import "google/rpc/status.proto";
+
+option cc_enable_arenas = true;
+option go_package = "google.golang.org/genproto/googleapis/api/expr/v1alpha1;expr";
+option java_multiple_files = true;
+option java_outer_classname = "EvalProto";
+option java_package = "com.google.api.expr.v1alpha1";
+
+// The state of an evaluation.
+//
+// Can represent an inital, partial, or completed state of evaluation.
+message EvalState {
+ // A single evalution result.
+ message Result {
+ // The id of the expression this result if for.
+ int64 expr = 1;
+
+ // The index in `values` of the resulting value.
+ int64 value = 2;
+ }
+
+ // The unique values referenced in this message.
+ repeated ExprValue values = 1;
+
+ // An ordered list of results.
+ //
+ // Tracks the flow of evaluation through the expression.
+ // May be sparse.
+ repeated Result results = 3;
+}
+
+// The value of an evaluated expression.
+message ExprValue {
+ // An expression can resolve to a value, error or unknown.
+ oneof kind {
+ // A concrete value.
+ Value value = 1;
+
+ // The set of errors in the critical path of evalution.
+ //
+ // Only errors in the critical path are included. For example,
+ // `(<error1> || true) && <error2>` will only result in `<error2>`,
+ // while `<error1> || <error2>` will result in both `<error1>` and
+ // `<error2>`.
+ //
+ // Errors cause by the presence of other errors are not included in the
+ // set. For example `<error1>.foo`, `foo(<error1>)`, and `<error1> + 1` will
+ // only result in `<error1>`.
+ //
+ // Multiple errors *might* be included when evaluation could result
+ // in different errors. For example `<error1> + <error2>` and
+ // `foo(<error1>, <error2>)` may result in `<error1>`, `<error2>` or both.
+ // The exact subset of errors included for this case is unspecified and
+ // depends on the implementation details of the evaluator.
+ ErrorSet error = 2;
+
+ // The set of unknowns in the critical path of evaluation.
+ //
+ // Unknown behaves identically to Error with regards to propagation.
+ // Specifically, only unknowns in the critical path are included, unknowns
+ // caused by the presence of other unknowns are not included, and multiple
+ // unknowns *might* be included included when evaluation could result in
+ // different unknowns. For example:
+ //
+ // (<unknown[1]> || true) && <unknown[2]> -> <unknown[2]>
+ // <unknown[1]> || <unknown[2]> -> <unknown[1,2]>
+ // <unknown[1]>.foo -> <unknown[1]>
+ // foo(<unknown[1]>) -> <unknown[1]>
+ // <unknown[1]> + <unknown[2]> -> <unknown[1]> or <unknown[2[>
+ //
+ // Unknown takes precidence over Error in cases where a `Value` can short
+ // circuit the result:
+ //
+ // <error> || <unknown> -> <unknown>
+ // <error> && <unknown> -> <unknown>
+ //
+ // Errors take precidence in all other cases:
+ //
+ // <unknown> + <error> -> <error>
+ // foo(<unknown>, <error>) -> <error>
+ UnknownSet unknown = 3;
+ }
+}
+
+// A set of errors.
+//
+// The errors included depend on the context. See `ExprValue.error`.
+message ErrorSet {
+ // The errors in the set.
+ repeated google.rpc.Status errors = 1;
+}
+
+// A set of expressions for which the value is unknown.
+//
+// The unknowns included depend on the context. See `ExprValue.unknown`.
+message UnknownSet {
+ // The ids of the expressions with unknown values.
+ repeated int64 exprs = 1;
+}