A RESTful web-service for the openLCA data conversion functionalities
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README.md

openLCA conversion service

This project provides a web-service for converting LCA process data sets. It is a Java application using the Grizzly HTTP Server and the import and export functions of the openLCA core modules. Currently, the conversion between the following data formats are supported:

Installation

In order to install the application a Java Runtime Environment >= 8 needs to be installed. Then, unzip the distribution package. It contains the application as a single jar file, a basic web UI, and a configuration file. You can start the application via the following command:

java -jar server.jar

On a Linux server you probably want to start the server as a background process from a shell. One solution to do this, is to use nohup:

nohup java -jar server.jar &

If your shell does not return the process ID (to kill the process later) you can get it via:

echo $!

Configuration

The default configuration file looks like this (without the comments):

{
  // the application host
  "host": "localhost",

  // the port of the application
  "port": 80,

  // path to a folder which contains the reference data and a file cache 
  "workspace": "./workspace",

  // an optional path to a folder with the web UI
  "ui": "./web",
}

Reference systems

The conversion service can be configured to run with different reference systems where a reference system contains a set of reference data like elementary flows, quantities, units etc. and mapping files which are used in the conversion. The data of the reference systems are stored under the directory refsystems of the workspace folder. Each reference system is stored in a sub-folder of the refsystems directory and is identified by the name of this sub-folder.

There is at least one default reference system which is created automatically on server startup if it does not exist. When a conversion request does not specify a reference system, the default reference system is taken in the conversion. The data of a reference system are stored in a file data.zip in the folder of the reference system. The content of the data.zip file should be provided in the openLCA JSON-LD format as produced by the openLCA export. Additionally, a set of mapping files (see below) can be provided in a sub-folder mappings in the data directory of the reference system.

On server startup, a data dump for each reference system is created if it does not exist yet. For each conversion against a reference system the dump of this system is loaded into memory and used for the conversion. Thus, to update the data of a reference system, just update the data.zip and mapping files, delete the dump folder and restart the server.

- workspace
  - refsystems
     - default
       + dump
       + mappings
       - data.zip
     - myrefsystem
       + dump
       + mappings
       - data.zip 

Mapping files

In the mappings folder of a reference system, mapping files can be specified. The mappings in these files are applied to the flows in the source format of a conversion and are format specific:

  • EcoSpold 1: ecospold_flow_map.csv
  • EcoSpold 2: ecospold_2_flow_map.csv
  • ILCD: ilcd_flow_map.csv
  • SimaPro CSV: sp_flow_import_map.csv

The mappings in these files should map to the data in the data.zip that you provide with the reference system (see above). For the EcoSpold 1+2 and ILCD format, the mapping files are simple CSV files with the following columns:

0: UUID of the flow in the source format
1: UUID of the reference flow in the database
2: a conversion factor f: <amount reference> = f * <amount source>

As flows in the EcoSpold 1 format have no UUIDs, MD5 based UUIDs are calculated from flow attributes in this case. The format of the SimaPro CSV mapping file is specified in the olca-modules repository. The folder default_mappings contains the mapping files that the conversion service uses by default.

Additionally, these mappings can be overwritten in each conversion request by providing a list of flow mappings directly in the conversion request: ...

How the conversion works

A client sends a conversion request to the conversion server which includes an URL to the respective process data set, the format of this data set, and the target format to which this data set should be converted. The conversion server then fetches all the required data from the data server using a format specific protocol. The converted data set with all associated resources (e.g. flow data sets etc.) are cached on the conversion server and a link to this data set is send back to the client:

How it works

Note that the client could be itself the back-end of an HTTP server that sends back the link to another client. The following data provider are currently supported:

Format Data provider Example URL
EcoSpold 1 Plain HTTP server providing the data set example from the Needs project
EcoSpold 2 Plain HTTP server providing the data set
ILCD soda4LCA example from the ELCD database
JSON LD openLCA CS e.g. http://localhost:8080/ws/public/browse/gdelta/refdata/PROCESS/e33fb2ad-5db5-4ee7-9486-515fce6fd46d

Building from source

This is a standard Maven project using the Kotlin compiler as Maven plugin. Thus you need to have Maven installed in order to compile the project. Also, it depends on the openLCA core modules which need to be installed first. For Windows, there is a build script build.bat which generates the distribution package:

cd olca-conversion-service
build

This will create the distribution package as olca-conv_<version+date>.zip in the target folder. To include the user interface, you need to also build it from source in the ui folder. We use Gulp as build tool for that:

cd olca-conversion-service/ui
npm install
gulp

The build script will package the UI in the distribution package if it can find it.

API

Conversion Request

  • URL

    /api/convert

  • Method

    POST

  • Data Parameters

    An JSON object that describes the conversion, e.g.:

  {
    // the URL to the source data set
    "url": "http://eplca.jrc.ec.europa.eu/ELCD3/...",
    
    // the format of the source data set
    // possible values: "EcoSpold 1", "JSON LD", or "ILCD"
    "sourceFormat": "ILCD",
    
    // the target format into which the data set should be converted
    "targetFormat": "EcoSpold 1"
  }
  • Success Response:

    • Code: 200
      Content: The conversion result as JSON object:
{
  // the name of the result package for getting all data set resources via
  // result request; see below
  "zipFile": "e.g. 123...2434_ECOSPOLD_1.zip",
  
  // the converted process data set
  "process": "xml or JSON",
  
  // the format of the conversion result; "EcoSpold 1", "JSON LD", or "ILCD"
  "format": "EcoSpold 1"
}
  • Error Response:

    • Code: 501, Not Implemented
      Content: Message about unimplemented data conversion or unknown format.

    • Code: 500, Internal Server Error
      Content: conversion error

Get Conversion Result

  • URL

    /api/result/:file

  • Method

    GET

  • URL Parameters

    The file name of a conversion result, e.g. "123...2434_ECOSPOLD_1.zip"

  • Success Response:

    • Code: 200
      Content: A zip file.
  • Error Response:

    • Code: 404, Not Found
      Content: "File <name> does not exist."

License

Unless stated otherwise, all source code of the openLCA project is licensed under the Mozilla Public License, v. 2.0. Please see the LICENSE.txt file in the root directory of the source code.