Personally Identifiable Information (PII)
This term is being used a lot in privacy based data processing. Following along with the Wikipedia article we see that PII data is any information … that can be used to distinguish or trace an individuals identity.
Legally the concept of PII data is not utilized by the European GDPR directive. Its scope is determined by the non-equivalent concept of personal data.
- Art. 4(1)
Personal data are any information which are related to an identified or identifiable natural person.
Correctly executing the Principles relating to the processing of personal data is at the origin of all the privacy related design decisions of Stream Machine.
This article states that:
- Article 5.1(a)
Personal data shall be processed lawfully, fairly and in a transparent manner in relation to the data subject (‘lawfulness, fairness and transparency’);
This is the responsibility of the DPO of the customer. Stream Machine can not identify the purposes and transparency associated with what purposes the customer has for collecting personal data. The DPO of the customer shall identify the purpose(s) for which certain personal data is collected and assign consent-levels to these purposes. These consent-levels link data processing goals with personal data attributes in the Stream Machine events.
The personal data owner (i.e. the person on your website, your client, your patient …) needs to give permission for the separate consent-levels, and the compact representation of these will be added to every event that gets processed by Stream Machine. 
Stream Machine removes the personal data aspect of all events upon acceptance in the event-gateway, by encrypting all personal data attributes (irrespective of any consent-levels given). These encrypted events do not enter any long-term or searchable storage in Stream Machine but are transported onwards to customer storage.
These encrypted events do not contain any personal data. Losing them might/will cost the customer business value, but no privacy issues.
- Article 5.1(c)
adequate, relevant and limited to what is necessary in relation to the purposes for which they are processed (‘data minimisation’);
Stream Machine collects events with or without personal data for all the combined purposes of a company. The encryption of all personal data in these events makes that they no longer contain personal data, unless one has access to the associated encryption keys.
The most common flow of data processing at Stream Machine is that the customer does not receive the encryption keys but instead requests a stream of decrypted events, where only events with adequate consent are visible, and with only those personal data attributes that correspond to the purposes.
Access to these data is delegated to the DPO of the customer. The data consumer in the company only has to explain the purpose of the data processing, whereupon the DPO will assign a set of required consent-levels, create an output stream with these events, and assign access credentials.
Stream Machine itself keeps the encrypted event data for 7 days  for technical purposes, so that a temporary failure of processing on the customers site does not cause data loss. During this time, the data can not be searched or queried in any meaningful way.
The key idea is that the customer does not keep decrypted data for longer than is required for the purpose of the processing, specifically these data should not be stored into long-term storage.