software should be easy to fire

i want to leave a fitness app without starting my training history again. that includes ath, the project i'm building.

the replacement needs to know where a measurement came from and what it means. if i corrected a result, it needs to understand the correction. an exported file is useful to the extent that the next system can interpret it.

i don't want the cost of reconstructing that history to be part of what keeps me paying. as a business, i'd want to know how many customers would stay if that cost disappeared. a customer who continues paying may like the service. they may also be avoiding the work of moving.

collecting useful measurements costs money. developing a device costs money. i expect to pay for useful services, and making records portable leaves a commercial model to work out.

i think a company should be able to sell those services through an interface it does not own. a wearable maker could supply measurements and analysis to another application with the person's permission. that would require an agreement about access and payment. it could give the company another way to reach people who want its capabilities.

ath keeps training and recovery data in a local sqlite database. local use requires no account or subscription. the record distinguishes measurements from what the athlete reports and retains revisions. the implementation is open.

another developer can build against that record. they still have to implement the reader and check that the meaning survives the transfer. i want that requirement to apply when someone replaces ath, too.