This page describes the convention for the PyWPS plugin to find and expose matlab processes.

Example

function [data] = oil_spill(track, volume)
% OIL_SPILL generate a dataset of an oil spill based on a track and total volume
%
% This is also part of the abstract
%
% input:
% track = linestring
% volume = double
%
% output:
% data = file.nc
%

Finding processes

Matlab functions can be exposed as WPS processes. The processes are found by putting matlab scripts in the directory that is exposed by the environment variable MATLAB_PROCESSES (analogue to PYWPS_PROCESSES). Matlab processes have the form of a matlab function, stored within a file with the name function.m.

WPS Process properties

The WPS process properties can be specified according to the table below. A process is a function and the properties are introspected from the comments by the following convention.

WPS Input properties

The input properties are the function arguments, which properties are introspected from the comments by the following convention.

WPS Matlab JSON input.

Because you can't call matlab functions dynamically we prepare input for the matlab processes in JSON messages.
These JSON messages have the following form.

// The following is an example of the CouchDB job queue
// The _id, _rev and _attachments are couchdb specific
{
   "_id": "723cd54245f4c578550768758b001564",
   "_rev": "6-e16ee53ee4642e2a3a080306f727a43f",
   "identifier": "tide_analysis",
   "dataInputs": {
       "timeseries": "data.xls",
       "location": "POINT(52 3)"
   },
   "_attachments": {
       "data.xls": {
           "content_type": "application/vnd.ms-excel",
           "revpos": 5,
           "length": 50688,
           "stub": true
       }
   }

WPS Matlab JSON input.

• install CouchDB from http://couchdb.apache.org/
• Via the Create Database link create a database called 'wps' (small case)
• Click on wps database,
• Via the New Document link create a new view.
• Manually update the source block (double click in the source block) by adding the following code:

  {
     "_id": "_design/views",
     "language": "javascript",
     "views": {
         "processes": {
             "map": "function(doc) {\n\n  if (doc.type == \"processes\") {\n  \n  doc.processes.forEach(function(element){\n  emit(element.identifier, element);\n  });\n}\n}"
         },
         "input": {
             "map": "function(doc) {\n  if (doc.type == \"input\") {\n     emit(null, doc);\n}\n}"
         },
         "output": {
             "map": "function(doc) {\n  if (doc.type == \"output\") {\n     emit(doc._id, doc);\n}\n}"
         },
         "matlab": {
             "map": "function(doc) {\n\n  if (doc.type == \"processes\" && doc.language == \"matlab\") {\n  \n  \n   emit(doc._id, doc);\n  }\n}"
         }
     }
  }
  

• If you modify an existing document, keep the original "_rev": "BUT KEEP THE AUTOMATIC REV CODE GENERATED BY YOUR COUCHDB"
• Test http://localhost:5984/wps/_design/views/_view/matlab to look like:

  {"total_rows":0,"offset":0,"rows":[
  
  ]}
  

• Switch to queue_url = 'http://localhost:5984' in the matlab wps runner wps.runner.run
• Check out this fork of pywps https://github.com/openearth/PyWPS and use branch couchprocesses
• configure your couchdb server in
  https://github.com/openearth/PyWPS/blob/couchprocesses/pywps/default.cfg