Conference Paper

Javascript Client Libraries for the (Former) Long Tail of OGC Standards


More and more information technology is moving into a cloud-based infrastructures for both data storage as well as user interfaces. With the advancement of browser technology, especially regarding Javascript engines, the user interfaces follow this move based on HTML5, also for mobile devices. One key advantage is clear: users always use the latest version and the environment is well controlled: an internet browser. General purpose libraries (e.g. jQuery), frameworks with user interfaces (e.g. Dojo Widgets) as well as web-application libs (e.g. AngularJS) facilitate the development of complex applications. In the geospatial domain, such frameworks and libraries are are successfully used to build complex applications and are often based on OpenLayers (OL) or Leaflet for mapping and visualisation. These libs support display of geospatial data coming from standardized view and feature services, most importantly the Open Geospatial Consortium’s (OGC) Web Map Service (WMS) and Web Features Service (WFS). Both server and client libraries are mature and have reached a very stable level and wide distribution.
What is missing today are generic libraries that operate at the same level of performance and quality to (i) access observation and time series data, for example coming from OGC Sensor Observation Services (SOS) as part of the Sensor Web Enablement (SWE) suite of standards, and (ii) control processes published online, for examples as an OGC Web Processing Service (WPS). These standards are less widespread than WMS and WFS but gain momentum as data volumes increase, for example with a myriad of smart sensors in the internet of things or new EO satellite missions, and subsequent requirements for sophisticated architectures for (event-based) processing and management of time series data. SWE standards have just reached their second versions; a new WPS standard is currently under development.
Observing these developments lead to the birth of two new open source Javascript library projects that are presented in this talk. SOS.js is a Javascript framework to access SOS data and build sophisticated lightweight browser applications for discovering and displaying time series data as plots, tables, and maps. It consists of two modules: core and user interface. wps-js is a Javascript client library for the WPS generating forms based on the standardized metadata from the service and interactively creating and submitting processing tasks. It uses a templating mechanism for XML building and an internal Javascript class hierarchy. Both libraries are based on OL’s request and response encoding. During the talk we will demonstrate sample applications build with the libraries and share experiences of developing client libraries for XML-based standardized web services with Javascript, which include programming as well as project build and management lessons. One goal for both libraries is to become independent of OL and provide service access with a minimal footprint, for example to display data without maps. Might OL and Leaflet eventually use these libraries instead of their own client implementations for SOS and WPS? We see an advantage of developing such small and focussed libraries maintained by field experts in these non-mainstream domains. We’ll happily discuss if this is the best approach and pose the following question: Is there a (technical, organisational) way to build a compatible Javascript client frameworks across all geo-service standards?
We conclude that Javascript is ready to handle raw (timeseries) data and it is used more than ever. Also, both the standards and their open source implementations are ready for operational deployments. So it is now time to spread them further by increasing the usability with good browser client applications based on small and flexible open source libraries. While the presented libraries are developed withing the 52°North communities we want to use this talk to actively reach out to members of other open source projects to seek collaborators and to organise interoperability tests to make these tools useful for a broader community.


Daniel Nüst, Matthes Rieke, Paul Breen

Presenter Biography: 

Daniel is a researcher at 52°North in the communities of geoprocessing and sensor web.

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