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Overview

CPS temporal data query allows the user to fetch data based on multiple filtering criteria. This data can be used by an analytical system to take decisions.

Filtering Criteria

As it is time-series data, it can be filtered based on three main criteria:

Datetime

• Data in last X hours 
• Data after a particular Data after specified DateTime (To be supported in Istanbul Release)
• Data between a date rangebefore specified DateTime 
• Last X records

DataTypes in CPS Core

• Dataspace & schema-set (To be supported in Istanbul Release)

• Dataspace & anchor (To be supported in Istanbul Release)
• Dataspace & multiple anchors - To improve performance, if there is a need to fetch data for multiple anchors.

Payload (To be partially supported in Istanbul Release)

• Based on a field in the payload. These criteria need schema-set to be fixed to search in the same set of anchors. The details of the format are defined here. 

We will implement only the basic APIs first and will add complex ones when required. 

Other Parameters 

There are other parameters, listed below, that can have an impact on the response. 

Assumptions

• Temporal database stores full information in the payload (CPS-192: Design data store for Temporal Service). 
• Data in the response body will always contain the entire payload data.

Payload Filter Format 

Anchor
payloadFilterFormat payloadFilterFormat

The data can be filtered, using JSON format, on one  field at any level, but it is important to provide the entire path from the root. The below JSON is used as an example to explain the filtering format

...

Proposed APIs

The GET Endpoints URI contains information about the anchors . But, and the format of the anchor data is different in both CPS Core and CPS-temporal, which can cause some confusion. Hence, two endpoint format have been proposed.The filtering rest of the filtering criteria are passed as query parameter. The below-mentioned query parameters are supported by all endpoints.

1. after - timestamp ( ISO Format) to consider data created after the specified Timestamp
2. payload simplePayloadFilter - to define payload filtering criteria
3. index pageNumber - to define the page number (required for pagination)
4. maxSize pageLimit - to limit the response size
5. pointInTime - to consider data changed or added before this time.
6. sortBy sort - to define the order of data in the result set

The response format for endpoints is the same and defined here

By Dataspace and Anchor

...

URL: GET /dataspaces/{dataspace-name}​/anchors/{anchor-name}​/history

Example: GET /dataspaces/{dataspace-name}​/anchors/{anchor-name}​?after=2021-03-21T00:00:00-0:00&payload={"idNearRTRIC":"1"}&maxSize=500

Endpoint Format B

URL: GET /dataspaces/{dataspace-name}​/anchor-data

Example: GET /dataspaces/{dataspace-name}​/anchor-data?anchor={anchor-name}​/history?after=2021-03-21T00:00:00-0:00&payloadsimplePayloadFilter={"idNearRTRIC":"1"}&maxSizepageLimit=500

By Dataspace and Schema-set

...

URL: ​GET /dataspaces/{dataspace-name}/anchors/history?schemaSet={schemaset-name}

Example: GET /dataspaces/{dataspace-name}/anchors?schemaSet={schemaset-name}&after=2021-03-21T00:00:00-0:00&payload={"idNearRTRIC":"1"}

Endpoint Format B

URL: ​GET /dataspaces/{dataspace-name}/anchors?schemaSet={schemaset-name}

Example: GET /dataspaces/{dataspace-name}/anchor-data?schemaSet={schemaset-name}&after=2021-03-21T00:00:00-0:00&payload={simplePayloadFilter={"idNearRTRIC":"1"}

Response 

Anchor
responseBody responseBody

...

{
  "nextRecordsLink": "cps-temporal/api/v1/dataspaces/{dataspace-name}/anchors/{anchor-name}/history?after=2021-03-21T00:00:00-0:00&payloadsimplePayloadFilter={"idNearRTRIC":"1"}&maxSizepageLimit=500&pointInTime=2021-04-21T00:00:00-0:00&indexpageNumber=2",
  "previousRecordsLink": "cps-temporal/api/v1/dataspaces/{dataspace-name}/anchors/{anchor-name}/history?after=2021-03-21T00:00:00-0:00&payloadsimplePayloadFilter={"idNearRTRIC":"1"}&maxSizepageLimit=500&pointInTime=2021-04-21T00:00:00-0:00&indexpageNumber=0",
  "records": [
    {
      "timestamp": "2021-03-21T00:00:00-0:00",
      "dataspace": "my-dataspace",
      "schemaSet": "my-schema-set",
      "anchor": "my-anchor",
      "data": {
        "status" : "UP"
      }
    }
  ]
}

...