diff --git a/specification/api-tracing.md b/specification/api-tracing.md
index 4834dfa895c..adaa7c28e23 100644
--- a/specification/api-tracing.md
+++ b/specification/api-tracing.md
@@ -344,8 +344,10 @@ A `Span` MUST have the ability to set attributes associated with it.
 An `Attribute` is defined by the following properties:
 
 - (Required) The attribute key, which must be a string.
-- (Required) The attribute value, which must be either a string, a boolean
-  value, or a numeric type.
+- (Required) The attribute value, which is either:
+  - A primitive type: string, boolean or numeric.
+  - An array of primitive type values. The array MUST be homogeneous,
+    i.e. it MUST NOT contain values of different types.
 
 The Span interface MUST provide:
 
diff --git a/specification/data-semantic-conventions.md b/specification/data-semantic-conventions.md
index cfda1326b78..627de6c59fc 100644
--- a/specification/data-semantic-conventions.md
+++ b/specification/data-semantic-conventions.md
@@ -6,6 +6,11 @@ Span attributes.
 * [Resource Conventions](data-resource-semantic-conventions.md)
 * [Span Conventions](#span-conventions)
 
+The type of the attribute SHOULD be specified in the semantic convention
+for that attribute. Array values are allowed for attributes. For
+protocols that do not natively support array values such values MUST be
+represented as JSON strings.
+
 ## Span Conventions
 
 In OpenTelemetry spans can be created freely and it’s up to the implementor to