diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5dbe0f0..415d87d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- `processing:expression` to describe how the data has been processed.
+
 ### Changed
 
 ### Deprecated
diff --git a/README.md b/README.md
index 5fd5cda..f79c0ab 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,7 @@ for the `providers` that have the role `producer` or `processor` assigned.
 
 | Field Name              | Type                | Description |
 | ----------------------- | ------------------- | ----------- |
+| processing:expression   | [Expression Object](#expression-object) | An expression or processing chain that describes how the data has been processed. |
 | processing:lineage      | string              | Lineage Information provided as free text information about the how observations were processed or models that were used to create the resource being described [NASA ISO](https://wiki.earthdata.nasa.gov/display/NASAISO/Lineage+Information). For example, `GRD Post Processing` for "GRD" product of Sentinel-1 satellites. [CommonMark 0.29](https://commonmark.org/) syntax MAY be used for rich text representation. |
 | processing:level        | string              | The name commonly used to refer to the processing level to make it easier to search for product level across collections or items. The short name must be used (only `L`, not `Level`). See the [list of suggested processing levels](#suggested-processing-levels). |
 | processing:facility     | string              | The name of the facility that produced the data. For example, `Copernicus S1 Core Ground Segment - DPA` for product of Sentinel-1 satellites. |
@@ -64,6 +65,21 @@ This list is not exhaustive and can be extended with the processing level specif
 | L3         | Data or retrieved environmental variables which have been spatiallyand/or temporally re-sampled (i.e., derived from level 1 or 2 products). Such re-sampling may include averaging and compositing.  A wide variety of sub-level products are possible (see below). | [ENVISAT Level-3](http://envisat.esa.int/level3/), [Sentinel-2 L3](https://s2gm.sentinel-hub.com/) |
 | L4         | Model output or results from analyses of lower level data (i.e.,variables that are not directly measured by the instruments, but are derived from these measurements) | |
 
+### Expression Object
+
+| Field Name | Type   | Description |
+| ---------- | ------ | ----------- |
+| format     | string | **REQUIRED** The type of the expression that is specified in the `expression` property. |
+| expression | \*     | **REQUIRED** An expression compliant with the `format` specified. The expression can be any data type and depends on the `format` given, e.g. string or object. |
+
+Potential expression formats with examples:
+
+| Format      | Type   | Description | Example |
+| ----------- | ------ | ----------- | ------- |
+| `gdal-calc` | string | A [`gdal_calc.py`](https://gdal.org/programs/gdal_calc.html) expression based on numpy syntax. | `A*logical_or(A<=177,A>=185)` |
+| `openeo`    | object | [openEO process](https://openeo.org/documentation/1.0/developers/api/reference.html#section/Processes) | [Example](https://raw.githubusercontent.com/Open-EO/openeo-processes/1.0.0/normalized_difference.json) |
+| `rio-calc`  | string | A [rio-calc](https://rasterio.readthedocs.io/en/latest/topics/calc.html) (RasterIO) expression | `(b4-b1)/(b4+b1)` |
+
 ## Relation types
 
 The following types should be used as applicable `rel` types in the
diff --git a/json-schema/schema.json b/json-schema/schema.json
index ee5492d..f129bd4 100644
--- a/json-schema/schema.json
+++ b/json-schema/schema.json
@@ -162,6 +162,11 @@
     },
     "requirements": {
       "anyOf": [
+        {
+          "required": [
+            "processing:expression"
+          ]
+        },
         {
           "required": [
             "processing:lineage"
@@ -187,6 +192,22 @@
     "fields": {
       "type": "object",
       "properties": {
+        "processing:expression": {
+          "title": "Processing Expression",
+          "type": "object",
+          "required": [
+            "format",
+            "expression"
+          ],
+          "properties": {
+            "format": {
+              "type": "string"
+            },
+            "expression": {
+              "description": "Any data type, depending on the format chosen."
+            }
+          }
+        },
         "processing:lineage": {
           "title": "Processing Lineage Information",
           "type": "string",