API

Abstract

An application programming interface (API) is a protocol intended to be used as an interface by software components to communicate with each other." -- Wikipedia:API

The API is implemented as a RESTful API, so it uses HTTP requests to store and read data. Thus, REST uses HTTP for all four CRUD (Create/Read/Update/Delete) operations.

PVLng supports all of them:

• PUT = create
• GET = read
• POST = update
• DELETE = delete

Data storage

For data storage we have two possibilities:

• Web front end for the master data, like channels and their relationships
• HTTP REST API for the operational channel data with HTTP PUT requests

The storage API accepts only one parameter data and routes it to the requested channel.

By default (load live data) system date and time will be used.

The model behind the channel represents the interface to the database.

Data readout

The data readout from the system must be done with HTTP GET requests.

The readout API analyzes the requests, identifies the channel and returns the extracted data.

The model behind the channel provides a defined interface to query data.

Requested format

The returned content type is detected by the requested file extension

• .json (or not set) → JSON
• .csv → Semicolon separated values
• .tsv → TAB separated values

Parameters

All parameters are optional.

Parameter name	Description	Format	default	Examples
start	Start timestamp for readout	string	00:00	YYYY-mm-dd HH:ii:ss seconds since 1970 relative from now sunrise
end	End timestamp for readout	string	24:00	YYYY-mm-dd HH:ii:ss seconds since 1970 relative from now sunset
period	Example	string	<empty>	[0-9.]+minutes [0-9.]+hours [0-9.]+days [0-9.]+weeks [0-9.]+month [0-9.]+quarters [0-9.]+years last readlast all
attributes	Return channel attributes as 1st data set / line	bool	0	Example
full	Return all data, not only timestamp and value	bool	0	Example
short	JSON: Return data as numeric indexed array, not as object with named keys	bool	0	Example