OGC API Processes with ZOO Project

Background on ZOO Project

The ZOO-Project is an open-source processing platform introduced in 2009, licensed under the MIT/X11 license. It facilitates integration and communication between existing software components using standards defined by the Open Geospatial Consortium (OGC).

The platform aims to ensure that processing tasks follow the FAIR principles: Findable, Accessible, Interoperable, and Reproducible.

The ZOO-Project supports the "OGC API - Processes" - Part 1 (Core) and Part 2 (Deploy, Replace, Undeploy) Standards.

Background on OGC API - Processes

Introduction to OGC API - Processes

The OGC API - Processes standard supports the wrapping of computational tasks into executable processes that can be offered by a server through a Web API and be invoked by a client application. It specifies a processing interface for communicating over a RESTful protocol using JavaScript Object Notation (JSON) encodings. The standard builds on concepts from the OGC Web Processing Service (WPS) 2.0 Interface Standard but provides a more modern approach, allowing for interaction with web resources using the OpenAPI specification. Importantly, it does not require implementation of a WPS interface.

Use Cases for OGC API - Processes

Government agencies, private organizations, and academic institutions use the OGC API - Processes standard to provide access to geospatial algorithms for processing data, including data from sensors. This distributed approach to processing allows for more capacity to handle large datasets and perform complex computations. The standard facilitates integration into existing software packages and supports scalable workflows for processing geospatial data.

Overview of "OGC API - Processes - Part 1 - Core"

The OGC API - Processes - Part 1: Core enables the execution of computational tasks such as raster algebra, geometry buffering, routing, constructive area geometry, and imagery analysis. It supports execution in two modes: synchronous, where the client waits for the execution to complete, and asynchronous, where the server processes the task in the background and the client periodically checks the status.

The table below outlines the main resources defined by the OGC API - Processes - Part 1: Core standard:

Overview of "OGC API - Processes - Part 2: Deploy, Replace, Undeploy (DRU)"

The OGC API - Processes - Part 2 specification extends the Core standard by defining additional capabilities for managing processes. It allows users to deploy, replace, and undeploy computational processes dynamically. This specification is useful for scenarios where processes need to be updated or removed, providing more flexibility and control over the server's computational tasks.

Here are the new resources introduced in Part 2:

OGC API - Process resources combining Part 1 and Part 2

Relation to Other OGC Standards

The OGC API - Processes standard modernizes and extends the capabilities offered by the OGC WPS. While the WPS standard provided a standardized interface for accessing computational services, the OGC API - Processes standard adopts a resource-oriented approach leveraging the OpenAPI specification. This results in better integration with modern web technologies and programming practices, addressing all the use cases supported by WPS and enabling more flexible and robust processing capabilities.

Learning Module overview

Tutorials

This series of tutorials provides a step-by-step guide to using the OGC API - Processes standard, covering the core functionalities from listing available processes to accessing the results of executed jobs. Each tutorial is designed to help you understand and implement the standard's capabilities in a practical way. The tutorials are provided with the following Jupyter Notebooks:

1. Deploy an application package.ipynb
2. List the deployed processes.ipynb
3. Describe the process.ipynb
4. Execute the process and monitor the execution.ipynb

Key Functionalities

Following these tutorials, the user will be able to cover all these key functionalities:

• List Available Processes: Learn how to retrieve the list of processes offered by the server. This step provides an overview of the available computational tasks, including process identifiers, titles, and descriptions.
• Deployment: Discover how to deploy a new process, such as a custom application package using Common Workflow Language (CWL). This tutorial explains the encoding options for deployment requests and how to handle deployment responses.
• Process Description: Understand how to obtain detailed descriptions of individual processes, including their inputs, outputs, and supported execution modes. This step provides insight into how to configure and execute specific tasks.
• Execution: Learn how to execute a process using the /processes/{processID}/execution endpoint. The tutorial covers submitting the execution request, passing inputs, and handling different execution modes.
• Monitor Execution: Discover how to track the progress of a submitted job. This tutorial explains how to monitor job status, retrieve progress updates, and check for completion.
• Access Results: Learn how to retrieve the results of a completed job. The tutorial covers accessing outputs like STAC catalogs or other data formats, allowing you to analyze the processed data.
• Job Management: Understand how to manage jobs, including listing all jobs, cancelling running jobs, and deleting completed or failed jobs. This tutorial explains how to maintain the server's job history and resource usage.