Use Cases Development Guidelines (RFC-020)

A period when the community can review the RFC (comment Docs).

Document Maintainers: Andi Gabriel Tan 2024. List of other contributors in Annex. 1.

Copyright: MIT license

Copyright © 2018-2024 Axiologic Research and Contributors.

This document is licensed under MIT license.


The purpose of this document is to summarize a general approach that use-case implementation can be used to develop projects using OpenDSU. Besides providing insights on the development phases, this document opens the black box represented by the blockchain and the DSU Storages by explaining how the integration with the legacy system should work.

1. Big Picture

Use cases will always involve different actors. In order to exchange data in a secure way with OpenDSU they will need an OpenDSU agent or wallet that will take care of all OpenDSU-related operations, such as the storage of the DSU’s key, the bricks storage in a local or remote server, or the anchoring of keys’ Anchor IDs in the blockchain. These agents can either be used locally (which is optimal to attain data self-sovereignty) or remotely in the cloud when it’s necessary (for example if you need the agent to be available 24 hours a day). We will often have a mix of local agents (or edge) where the most sensitive data will be stored and cloud agents to get the benefits of cloud storage, such as availability. The data stored in the DSU is only accessible using the associated keys. These keys will be resolved to obtain necessary information about the brick storages or anchoring services that will allow the agents to reconstruct the DSU in its execution environment. These mechanisms allow the keys’ owners to keep data hidden from the other actors. The highest key of a family (SeedSSI) is providing total control over the DSU it is associated with. In order for these key owners to share control of their DSU, they can send the same key to their collaborators. They can also decide to give restricted access to their DSU without sharing the original key, by using key derivation processes to create new keys that they will be able to share safely (e.g. SReadSSI, for read-only access). Use cases should use a mix of keys to create access control policies for their DSUs.

2.1. Development Process from the OpenDSU Perspective

We can see a DSU as a record in a table in a relational database for simplicity, but the implementation is different from this. As stated above, access to a DSU is only done with a KeySSI that is unique for each DSU. When designing a use case, the architect creating an OpenDSU-based solution should go through the steps explained in this section.

DSU Types

A DSU is one unique technology enabling safe storage and safe transfer of data through key ownership. Still, DSUs can be created for different purposes, different processes and/or for different people. It is possible to configure these different DSUs under specific types to facilitate their replication. Each use case will have to develop specific DSU Types to achieve their goals. DSU Types are similar in their design to Object Oriented Programming classes or to the design of tables in relational database models. They are neither classes nor tables, but they play a similar role. In the following example, we can see that different DSUs were created for different steps of a product supply chain. We can imagine that different people would need different types of access to these DSUs. The transporter would need access to create and modify the shipment DSU, while the customer would only own a key to read the same DSU to see their order and know at what time they will receive the shipment.

DSU Main KeySSI type KeySSI for mutable Real DSU
Order Status    
Shipment Line    

Access control table (defines communication lines between agents)

DSU types Created by Write mode (Anchoring) Read Only Sharing with Existence Shared with
Orderline PHA PHA MAH HA
Order Status PHA PHA, DST   HA
Shipment Line DST DST   HA
Batch MAH MAH   HA

DSU Mounting Relationships

DSU Mounted DSU Mounted Points Mounting Way (write, read, existence)
Order Orderline types /orderlines/1 /orderline/2 /orderline/3 …. existence
Order Status      
Shipment Line      
Batch Batch type /batch read

Shared DSUs with Statuses (micro-ledgers)

Order Statuses for Order Description
At WHS  
At MAHs  

Choose a Blockchain Domain for the Use Case

In OpenDSU, blockchains are used for anchoring. In other words, all anchor IDs of the DSUs will be written in a decentralized and immutable ledger. In order for all actors present in the use case to communicate, we have to choose a common Blockchain Domain from which we will be able to get the correct ledger system (e.g. ePI).


Tra ding (Agent) Partner Role & Desc ription Blockchain Domain for Bricks
MAH   Manufacturer e.g. msd.epi, nvs.epi. pl.epi
PHA   Pharmacy  
WHS   Wholesaler  
DST   Distributor  
HA   Health Authorities/External Auditors  
PAT   Patient  
COU   Courier  
HOS   Hospital  

3. Generic components for all use cases

In this section, we assume that in all use cases we were able to identify agents, legacy applications, the blockchain used for anchoring DSUs, and the bricks storage used to store encrypted DSUs off-chain (or near-chain: some data directly anchored and other off-chain). The cloud and edge agents are special applications created independently for each use case but reusing the same general techniques. The legacy applications include existing software such as SAP, ServiceNow etc., that will be integrated with Pharmaledger using a new component that we describe below as “DSU-Wizard”. In the following subchapters, we will describe the concept of agents and the DSU-Wizard. All information about the other components can be found in the OpenDSU documentation.


An agent can have access to one or more wallets, and each wallet has access to one or more DSUs. In general, the user who controls an agent is a person and not a company, but depending on the role in the company, it is possible to imagine a superuser (e.g. a manager) supervising the wallets of other employees.

Edge Agent

An Edge Agent is a software entity that securely holds data and keys on behalf of a user, locally. The edge agent could run on a computer, a mobile device or a browser. Running user interaction through edge Agents is the best way to obtain data self-sovereignty and provide control of data to its owner/patient, without intermediaries. Sometimes, in order to satisfy certain business needs, it is necessary to have Cloud Agents that are under the control of companies or external intermediaries.

Cloud Agents

A Cloud Agent is a software entity that securely holds data and keys on behalf of a company remotely. As for edge agents, cloud agents have access to one or multiple wallets and those wallets contain DSUs. The advantage of cloud agents is that they can be available 24 hours a day from anywhere. Cloud agents are generally controlled and maintained by a company and not by a person. However, concrete people controlling edge agents can control the same wallets as the cloud agents if they own the same keys.

DSU Wizard

The integration between legacy systems and the world of the OpenDSU Agents capable of manipulating DSUs is managed by a component that we call “DSU Wizard”. The DSU Wizard is a set of Web APIs that are called from the external systems (the legacy systems). The Purpose of the DSU Wizard is for the OpenDSU SDK to be used by the legacy system code by offering a set of simple Web APIs to create or update the DSUs as required by businesses. As the name implies, the DSU Wizard is a set of APIs that should be called in a specific order, starting from the initialization of a creation process until the actual creation of bricks and anchors, as expressed in the above diagram. The DSU Wizard is also capable of updating an already existing DSU, as depicted above.

4. The standard model of operations

DSUs can be seen as an extension of the blockchain. Each DSU is a micro-ledger (a set of operations or transactions validated by anchoring in a parent blockchain) and any imaginable use case only updates the status of DSUs using DSU APIs. Being a micro-ledger, it offers an alternative method to implement “off-chain” smart contracts in a way that does not suffer the same problems as on-chain smart contracts regarding confidentiality and scalability.

5. Annexes (examples/diagrams)

5.1. Major components

5.2. Indirect and direct participants

5.3. Generic Architecture

AnchorIDs are stored on the ePI Blockchain (Consortium Blockchain). The ePI Blockchain is readable by everyone (Public), but only writable (AnchorID) for authorized parties, such as Pharma Companies.

5.4. ePI Architecture

5.5. DSU Model design example

5.6. Other use cases

5.7. Control tower


  1. Axiologic Research: New content and improvements. Original texts under PharmaLedger Association and Novartis funding. MIT licensed content accordingly with the contracts. Publish and maintain the site.

  2. PharmaLedger Project: Review, feedback, observations, new content, and corrections MIT licensed accordingly with the consortium agreements.

  3. PrivateSky Research Project: MIT licensed content accordingly with the contracts.

Annex 1. Contributors

Current Editors Email
Andi-Gabriel Țan
Contributors Axiologic Research Email
Adrian Ganga
Andi-Gabriel Țan
Cosmin Ursache
Daniel Sava
Nicoleta Mihalache
Valentin Gérard
PrivateSky Contributors Email
Alex Sofronie (DPO)
Cosmin Ursache (UAIC)
Daniel Sava (HVS, AQS)
Daniel Visoiu (SGiant)
Lenuța Alboaie (UAIC)
Rafael Mastaleru (RMS)
Sînică Alboaie (UAIC)
Vlad Balmos (Code932)
PharmaLedger Contributors Email
Ana Balan (RMS)
Bogdan Mastahac (RMS)
Cosmin Ursache (RMS)
Rafael Mastaleru (RMS)