Where to find the PSD2 technical specification?
Here is the UK standard.
https://www.openbanking.org.uk
Also there is a linkedin group to connect developers working on PSD2 and Openbanking with banks, regulators and suppliers here.
https://www.linkedin.com/groups/12069802
I got an answer from the "owner" of the OBP project, I'm posting it verbatim:
Regarding the current status, Open Bank Project API develop branch currently supports OBP API specs 1.2.1 through 3.0.0
We also have an ISO20022 connector (PAIN) for initiating payments.
You can read the OBP specs here:
https://apiexplorersandbox.openbankproject.com/
or use the Swagger:
https://apisandbox.openbankproject.com/obp/v1.4.0/resource-docs/v3.0.0/swagger
or Resource Docs (our own format):
https://apisandbox.openbankproject.com/obp/v1.4.0/resource-docs/v3.0.0/obp
(the Swagger / Resource Doc links can also be found at the bottom of the API Explorer)
Regarding PSD2, PSD2 doesn't explain exactly how countries should comply (e.g. it doesn't define URLs etc.). However, it does say in Article 28 point 3: "Account servicing payment service providers shall also ensure that the dedicated interface uses ISO 20022 elements, components or approved message definitions, for financial messaging".
This is why STET (the recent French standard) uses field names like "PmtTpInf", "InstrPrty", "SvcLvl" and "Cd" etc.
In addtion to the OBP standards mentioned above, we aim to support:
An ISO 20022 version of OBP. This will most likely be requested using a different Mime type on the current OBP URLs and will be implemented as an automatic translation of OBP terms to ISO20022 equivelents (where they exist). We'll probably support ISO20022 short field names and also longer type names (which are verbose but are more self describing).
- UK Open Banking standard
- STET (French)
- Other Country standards.
Thus OBP API will be able to surface multiple standards using one OBP instance and backend connector. It will provide easy to use REST APIs (OBP) and less easy to read ISO20022 interfaces for compliance.
Hope that helps.
p.s. here is STET: https://www.stet.eu/assets/files/PSD2/API-DSP2-STET_V1.2.2.pdf
If you are looking for a technical standard that is intended to be applicable across all PSD2 countries, you should check out the Berlin Group spec.
The Open Banking spec is somewhat UK specific, it might be sufficient if you only need to support UK market, or you could extend it to support other products/markets (e.g. SEPA payments).