Software Developer Guide Introduction
This software developer guide is designed to outline the technical details of getting a Home Performance XML (HPXML) implementation up and running. HPXML is an expansive standard data format based on XML and maintained by the Building Performance Institute’s Working Group 5 (BPI WG-5). For more information on the BPI data standards and their relation to HPXML see What are the BPI Data Standards?.
The HPXML format is defined by a set of XML Schema (XSD) documents that outline all the acceptable data elements, their structure, and relation to one another. The schema itself is very flexible. Almost none of the elements are required, which allows for any level of detail in home performance data to be transmitted in the format. This level of flexibility is very useful but it also can be dangerous for the software developer. Two developers could each create an implementation that would represent their data in valid HPXML, but would be very divergent. The purpose of this guide is to document the assumptions that are not codified in the schema that are necessary to write and interpret HPXML documents across platforms.
The majority of the assumptions and recommendations here come from the set of pilot implementations in the Audit-Upgrade Use Case. This guide primarily documents lessons learned from those pilots. As other use cases present themselves, this guide will be augmented appropriately.
BPI Working Group 5
One of the best resources you will have available to you as you develop to HPXML is BPI Working Group 5 (a.k.a. HPXML Working Group). Many of the current developers are there. They have a lot of experience in getting HPXML working and can help you avoid costly pitfalls.
To join the working group send an email to hpxml@homeperformance.org.
GitHub
The HPXML schemas, example files, and this guide are all maintained on GitHub. You will always be able to find the latest version of the schemas there. Additionally as the schemas evolve over time you can be connected to and influence that process.
