Centralize attributes definition

Signed-off-by: Bogdan Drutu <[email protected]>

specification/common/common.md

@@ -0,0 +1,21 @@
+# Context
+
+<details>
+<summary>
+Table of Contents
+</summary>
+
+- [Attributes](#attribute)
+
+</details>
+
+## Attributes
+
+Attributes represent a list with zero or more key:value pairs (`Attribute`). An `Attribute` is defined by the following properties:
+
+- (Required) The attribute key, which MUST be a non-`null` and non-empty string.
+- (Required) The attribute value, which is either:
+  - A primitive type: string, boolean or double (IEEE 754-1985) and int64.
+  - An array of primitive type values. The array MUST be homogeneous,
+    i.e. it MUST NOT contain values of different types. For protocols that do
+    not natively support array values such values MUST be represented as JSON strings.

specification/overview.md

@@ -54,11 +54,8 @@ Each **Span** encapsulates the following state:
 
 - An operation name
 - A start and finish timestamp
-- A set of zero or more key:value **Attributes**. The keys must be strings. The
-  values may be strings, bools, or numeric types.
-- A set of zero or more **Events**, each of which is itself a key:value map
-  paired with a timestamp. The keys must be strings, though the values may be of
-  the same types as Span **Attributes**.
+- [**Attributes**](./common/common.md#attributes)
+- A set of zero or more **Events**, each of which is itself a tuple (timestamp, name, [**Attributes**](./common/common.md#attributes)). The name must be strings.
 - Parent's **Span** identifier.
 - [**Links**](#links-between-spans) to zero or more causally-related **Spans**
   (via the **SpanContext** of those related **Spans**).
@@ -300,6 +297,4 @@ Span attributes.
 * [Metrics Conventions](metrics/semantic_conventions/README.md)
 
 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.
+for that attribute. See more details about [Attributes](./common/common.md#attributes).

specification/resource/sdk.md

@@ -30,14 +30,13 @@ The SDK must support two ways to instantiate new resources. Those are:
 
 ### Create
 
-The interface MUST provide a way to create a new resource, from a collection of
-attributes. Examples include a factory method or a constructor for a resource
+The interface MUST provide a way to create a new resource, from [`Attributes`](../common/common.md#attributes).
+Examples include a factory method or a constructor for a resource
 object. A factory method is recommended to enable support for cached objects.
 
 Required parameters:
 
-- a collection of name/value attributes, where name is a string and value can be one
-  of: string, int64, double, bool.
+- [`Attributes`](../common/common.md#attributes)
 
 ### Merge
 

specification/trace/api.md

@@ -202,7 +202,7 @@ the entire operation and, optionally, one or more sub-spans for its sub-operatio
 - A [`SpanKind`](#spankind)
 - A start timestamp
 - An end timestamp
-- [`Attribute`s](#set-attributes), a collection of key-value pairs
+- [`Attributes`](../common/common.md#attributes)
 - A list of [`Link`s](#add-links) to other `Span`s
 - A list of timestamped [`Event`s](#add-events)
 - A [`Status`](#set-status).
@@ -281,8 +281,7 @@ The API MUST accept the following parameters:
   See [Determining the Parent Span from a Context](#determining-the-parent-span-from-a-context)
   for guidance on `Span` parenting from explicit and implicit `Context`s.
 - [`SpanKind`](#spankind), default to `SpanKind.Internal` if not specified.
-- `Attribute`s - A collection of key-value pairs, with the same semantics as
-  the ones settable with [Span::SetAttributes](#set-attributes). Additionally,
+- [`Attributes`](../common/common.md#attributes). Additionally,
   these attributes may be used to make a sampling decision as noted in [sampling
   description](sdk.md#sampling). An empty collection will be assumed if
   not specified.
@@ -334,8 +333,7 @@ description](../overview.md#links-between-spans).
 A `Link` is defined by the following properties:
 
 - (Required) `SpanContext` of the `Span` to link to.
-- (Optional) One or more `Attribute`s with the same restrictions as defined for
-  [Span Attributes](#set-attributes).
+- (Optional) One or more `Attribute`s as defined [here](../).
 
 The `Link` SHOULD be an immutable type.
 
@@ -393,15 +391,7 @@ propagators.
 
 #### Set Attributes
 
-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 non-`null` and non-empty string.
-- (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.
+A `Span` MUST have the ability to set [`Attributes`](../common/common.md#attributes) associated with it.
 
 The Span interface MUST provide:
 
@@ -439,8 +429,7 @@ with the moment when they are added to the `Span`.
 An `Event` is defined by the following properties:
 
 - (Required) Name of the event.
-- (Optional) One or more `Attribute`s with the same restrictions as defined for
-  [Span Attributes](#set-attributes).
+- (Optional) [`Attributes`](../common/common.md#attributes).
 - (Optional) Timestamp for the event.
 
 The `Event` SHOULD be an immutable type.