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diff --git a/bundles/org.simantics.scl.expressions/src/org/simantics/scl/expressions/EnvironmentDescription.java b/bundles/org.simantics.scl.expressions/src/org/simantics/scl/expressions/EnvironmentDescription.java
new file mode 100644
index 000000000..0ae0a729b
--- /dev/null
+++ b/bundles/org.simantics.scl.expressions/src/org/simantics/scl/expressions/EnvironmentDescription.java
@@ -0,0 +1,24 @@
+package org.simantics.scl.expressions;
+
+/**
+ * Describes an environment for evaluating expressions.
+ * The description includes the names and types of the
+ * environment variables, but not necessarily the values.
+ * The values are obtained using the ContextualValues
+ * given by successfully resolved variables. 
+ * @author Hannu Niemistö
+ * @param <Context>
+ */
+public interface EnvironmentDescription<Context> {
+    /**
+     * Tries to resolve an environment variable
+     * with a given name. Returns <code>null</code>
+     * if there is no such variable. If variable is
+     * found, returns ContextualValue that can be
+     * used to obtain the value of the environment 
+     * variable with a suitable context.
+     * @param name
+     * @return
+     */
+    ContextualValue<Context> resolve(String name);
+}