2.0 HOLOCHAIN DESIGN & ARCHITECTURE

2.1 What is the difference between an hApp and DNA in Holochain

In Holochain, an hApp (short for “Holochain application”) and a DNA (short for “Distributed Network Application”) are related concepts, but they have different meanings and functions.

An hApp is a higher-level abstraction that represents a complete application built on top of Holochain. It typically consists of multiple zomes, UI components, and other application-specific code that work together to provide a specific set of functionality to users. An hApp is what end-users interact with, and it typically provides a user-friendly interface for accessing the application’s features.

On the other hand, a DNA is a lower-level construct that represents the core logic and data structures of a Holochain application. It consists of one or more zomes, which contain the entry definitions, validation rules, and other code that defines the data structures and business logic of the application. A DNA also includes cryptographic keys and other metadata that are necessary for participating in the Holochain peer-to-peer network.

In other words, an hApp is a complete application that runs on top of Holochain, while a DNA is the underlying code and data structures that make up that application. An hApp can be thought of as a user-facing interface that provides access to the functionality provided by the DNA. The DNA, in turn, provides the core logic and data structures that enable the application to function in a decentralized and distributed manner.

2.2 What is the difference between a DNA and Zome in Holochain

In Holochain, a DNA (Distributed Network Application) and a Zome are related concepts, but they have different meanings and functions.

A DNA represents the core logic and data structures of a Holochain application. It consists of one or more Zomes, as well as cryptographic keys and metadata necessary for participating in the Holochain peer-to-peer network. The DNA defines the rules for how agents (individual nodes in the Holochain network) can interact with each other, how data is stored and retrieved, and how transactions are validated and committed to the distributed ledger.

A Zome, on the other hand, is a modular component within a DNA that encapsulates a specific set of functionality. Each Zome defines a set of entry types and rules for validation and access control over the data stored within those entries. Zomes are the building blocks of a DNA, and they provide a way to organize and separate the different aspects of an application’s functionality.

In summary, a DNA is the complete Holochain application, consisting of one or more Zomes, while a Zome is a modular component within the DNA that provides a specific set of functionality. Each Zome has its own set of entry definitions and validation rules, which are used to control access to and interaction with the data stored within that Zome.

2.3 What are fields within Zomes in Holochain called

In Holochain, fields within zomes are called “entry definitions”. An entry definition is a code construct that defines a data structure for storing data in a Holochain application. Each entry definition specifies the fields that make up the data structure, as well as any validation rules or constraints on those fields.

An entry definition is defined within a zome, which is a modular component of a Holochain application that encapsulates a specific set of functionality. Each zome can contain one or more entry definitions, which represent the data structures used by that zome.

The fields within an entry definition are similar to the columns within a database table or the properties of an object in object-oriented programming. They define the individual pieces of data that make up the larger structure, and provide a way to organize and access that data.

In Holochain, the fields within an entry definition are typically defined as key-value pairs, where the key is the name of the field and the value is a data type that specifies the kind of data that can be stored in that field. Some of the common data types used in Holochain include string, boolean, number, and address, among others.

2.4 How many fields can a zome in Holochain contain

The number of fields that a zome in Holochain can contain depends on the complexity and size of the data being stored. There is no fixed limit on the number of fields that a zome can contain. However, it is generally recommended to keep zomes focused on a specific domain or use case, and to limit the number of fields to the essential ones required for that use case. This can help to simplify the zome logic and reduce the potential for errors. Additionally, larger zomes with many fields may impact performance and scalability of the Holochain application.

2.5 How do I set up a Zome in Holochain

To set up a Zome in Holochain, you will need to use the Holochain CLI (command-line interface) tool, which provides commands for creating and managing Holochain projects, DNA definitions, and Zomes.

Here are the basic steps for setting up a Zome:

  1. First, make sure you have installed the Holochain CLI tool on your local machine. You can find instructions for installing it on the Holochain documentation website.
  2. Create a new Holochain project by running the following command in your terminal:

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hc init my-project-name

This will create a new directory called my-project-name with the basic files and folders you’ll need for your project.

  1. Navigate into the project directory by running:

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cd my-project-name

  1. Generate a new DNA definition file by running:

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hc dna init my-dna-name

This will create a new directory called my-dna-name within your project directory, containing the basic files you’ll need for your DNA.

  1. Navigate into the my-dna-name directory by running:

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cd my-dna-name

  1. Generate a new Zome within the DNA by running:

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hc generate zome my-zome-name

This will create a new directory called my-zome-name within your DNA directory, containing the basic files you’ll need for your Zome.

  1. Define your Zome functions by editing the my-zome-name/src/lib.rs file. This is where you’ll define your Zome entry types, validation rules, and business logic.
  2. Once you have defined your Zome functions, build your DNA by running the following command in your DNA directory:

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hc package

This will compile your DNA and create a *.dna.json file in the target directory of your DNA directory.

  1. You can then install your DNA onto your local Holochain conductor (a local instance of the Holochain runtime) by running the following command in your DNA directory:

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hc run –agent-name my-agent-name

This will start a local Holochain conductor and install your DNA onto it under the specified agent name. You can then use the Holochain CLI tool to interact with your DNA and Zome functions.

These are just the basic steps for setting up a Zome in Holochain. There are many additional features and options available, depending on the complexity of your project and the requirements of your application. For more information, I would recommend consulting the Holochain documentation and community resources, which provide detailed tutorials and examples for developing Holochain applications.

2.6 How are fields named within Zomes in Holochain

In Holochain, fields within zomes are typically named using snake_case convention, which means using lowercase letters and underscores to separate words. For example, a field that represents a person’s first name might be named “first_name”. This convention makes it easier to read and understand the code, and also helps to avoid naming conflicts with other variables or functions.

2.7 Does Holochain have a security model for data ownership?

Yes, Holochain has a security model that allows for data ownership and control. Holochain is built on a distributed architecture, which means that data is stored locally on each user’s device rather than on a centralized server. This allows for greater control and ownership over personal data, as each user has full control over their own data and can choose who to share it with.

Holochain also uses cryptographic techniques to ensure the privacy and security of user data. For example, data is encrypted before being stored on a user’s device, and communication between devices is encrypted as well. In addition, Holochain has built-in identity management features, such as the ability to create and manage user profiles and the ability to specify access permissions for data.

Overall, Holochain’s security model is designed to provide users with greater control and ownership over their data, while also ensuring the privacy and security of that data through the use of advanced cryptographic techniques.

2.8 Can you give me an example of a Holochain Zome containing employee data

Sure, here is an example of a Holochain Zome containing employee data:

Assuming we are building a Human Resources application, we can create a employee Zome which contains the following CRUD functions:

  1. create_employee – creates a new employee
  2. get_employee – retrieves an employee by ID
  3. update_employee – updates an employee by ID
  4. delete_employee – deletes an employee by ID

Each employee record can contain fields such as:

  • id – unique identifier for the employee
  • name – employee’s full name
  • dob – employee’s date of birth
  • address – employee’s address
  • phone – employee’s phone number
  • email – employee’s email address
  • salary – employee’s salary
  • hire_date – date when the employee was hired
  • termination_date – date when the employee was terminated (if applicable)

The fields in the employee record can be named using conventional naming standards such as snake_case or camelCase.

2.9 Can I import data to Holochain from a CSV file

Yes, it is possible to import data from a CSV file into a Holochain application. However, the specific process will depend on the design of your Holochain application and the format of the CSV file.

Here is a general process for importing data from a CSV file into a Holochain application:

  1. Define the data schema: The first step is to define the data schema for your Holochain application, which specifies the data structure and validation rules. This will involve creating the appropriate DNA code and defining the necessary entry types, validation rules, and other data structures.
  2. Convert the CSV file to a compatible format: The next step is to convert the CSV file into a format that is compatible with your Holochain application. This may involve using a tool to convert the CSV file into JSON or another format that can be easily parsed by your Holochain application.
  3. Parse the data and create entries: Once you have the data in a compatible format, you can use Holochain’s API to parse the data and create new entries in the DHT. This will involve using the appropriate Holochain functions to create new entries for each row of data in the CSV file.
  4. Validate the data: After importing the data, you will need to validate it to ensure that it conforms to the data schema for your Holochain application. This will involve using the appropriate validation functions in your Holochain code to check that the data is valid and consistent with the schema.
  5. Test and refine the process: Finally, you should test the process of importing data from a CSV file and refine it as necessary to ensure that it works reliably and efficiently.

Overall, importing data from a CSV file into a Holochain application is possible but will require careful planning and implementation. You may want to consult with experienced Holochain developers or seek out training resources to help you get started.

2.10 Can I install a pre-built zome component on a Holochain application framework

Yes, you can install a pre-built zome component on a Holochain application framework.

To do this, you’ll need to follow these steps:

  1. Make sure you have a Holochain development environment set up on your computer. You can download it from the Holochain website and follow the installation instructions.
  2. Find the pre-built zome component you want to install. You can usually find this on the developer’s website or Github repository.
  3. Download the zome component files to your computer.
  4. Open the Holochain application directory and navigate to the “zomes” folder.
  5. Create a new folder for the new zome component you want to install.
  6. Copy the downloaded zome files to this new folder.
  7. Modify the “dna.json” file to include the new zome component. You’ll need to add the zome name, description, and file paths to the “dna.json” file.
  8. Use the Holochain command-line interface to build and install the new zome component on your application. The command will vary depending on your specific application, but it will typically be something like “hc package && hc run”.
  9. Once the installation is complete, you should be able to use the new zome component in your Holochain application.

Note that some zome components may require additional setup or configuration steps. Make sure to follow any instructions provided by the developer to ensure that the zome component is installed correctly and functioning properly.

2.11 What is bootstrapping in Holochain

Bootstrapping in Holochain refers to the process by which a new node or agent joins an existing Holochain network. When a new node is created, it must establish a connection to the network and download the necessary metadata and data structures in order to participate in the network.

During the bootstrap process, a new node typically performs the following steps:

  1. Identify and connect to existing nodes in the network.
  2. Download and verify the necessary metadata and data structures, such as the DHT (Distributed Hash Table) and the DNA (Distributed Network Application).
  3. Participate in the network by sharing and receiving data with other nodes.

Once a node has completed the bootstrap process, it can start to contribute to the network and participate in the validation and distribution of data.

Holochain’s bootstrapping process is designed to be lightweight and efficient, allowing new nodes to quickly join the network without requiring significant computational resources. Additionally, the peer-to-peer nature of the network means that nodes can join and leave the network dynamically without affecting the overall functionality of the system.

2.12 Are source chains a similar architecture to blockchain

While source chains in Holochain have some similarities to blockchains, they employ a different architectural approach.

In a blockchain, a linear chain of blocks is used to record transactions or data in a chronological order. Each block contains a set of transactions, along with a reference to the previous block, forming an immutable chain. This ensures that the order of transactions is preserved and provides a mechanism for consensus among participants.

In contrast, Holochain’s source chains are individual chains maintained by each node in the network. Each node has its own source chain, which records its actions and interactions within the application. These source chains are not shared or replicated in their entirety across the network like in a blockchain. Instead, nodes interact through a distributed hash table (DHT) to exchange data and verify each other’s actions.

Holochain achieves a level of validation and consensus through cryptographic techniques. Nodes can request cryptographic proofs and signatures from other nodes to verify the integrity and authenticity of the data. This approach allows for high scalability and efficiency as nodes only need to process and store their own data and the data they choose to replicate.

So, while both blockchains and source chains aim to provide a record of transactions or actions, source chains in Holochain differ in terms of their individual nature, lack of global replication, and reliance on cryptographic validation rather than a shared consensus mechanism.

2.13 Can Holochain Zome names include underscores

Yes, Holochain Zome names can include underscores. However, it is generally recommended to use camelCase naming convention instead of underscores in Holochain development. This is because the underscore character can sometimes cause issues when used in function or variable names in some programming languages, whereas camelCase is a widely accepted convention that avoids such issues.

2.14 Can Holochain zomes be interchanged with other zomes of the same name in a DNA

In Holochain, each zome is uniquely identified by its name and cannot be interchanged with another zome of the same name in a DNA. Each zome represents a distinct module of functionality within the DNA and is responsible for managing its own data and business logic. Interchanging zomes of the same name could cause data inconsistencies and break the functionality of the DNA. Therefore, it’s important to maintain consistency in zome naming conventions and avoid any naming conflicts when developing a Holochain application.

2.15 Could Holochain be described as a microservices solution

While Holochain shares some characteristics with microservices architecture, it is not typically described as a microservices solution in the traditional sense. Here’s why:

  1. Architecture: Microservices architecture typically refers to a software architecture pattern where an application is composed of loosely coupled, independently deployable services that communicate with each other through well-defined APIs. Holochain, on the other hand, is a framework for building decentralized applications (dApps) with a peer-to-peer architecture. It focuses on distributed data integrity, peer collaboration, and agent-centric design rather than microservices-based service decomposition.
  2. Granularity: In a microservices architecture, services are typically fine-grained and focused on specific functionalities or business capabilities. Each microservice can be developed, deployed, and scaled independently. Holochain, however, is more focused on building distributed, agent-centric applications where the emphasis is on data integrity, validation rules, and secure peer interactions rather than service decomposition.
  3. Communication and Scalability: Microservices architecture often relies on inter-service communication mechanisms like REST APIs, message queues, or event-driven architectures. In Holochain, communication and data exchange happen in a peer-to-peer manner through cryptographic protocols without relying on centralized messaging or communication patterns. The scalability mechanisms and considerations for microservices and Holochain applications may also differ.

That said, Holochain can provide certain benefits similar to microservices architecture, such as modular development, interoperability, and the ability to combine different components or modules to build complex applications. Holochain’s agent-centric approach allows developers to build specialized modules or components that can interact and collaborate in a decentralized manner. This flexibility can support modular development and composition similar to microservices.

In summary, while Holochain shares some characteristics with microservices architecture, it is a distinct framework focused on decentralized application development, peer collaboration, and data integrity rather than being a traditional microservices solution.

2.16 How would a successful applicant transfer data from their individual node to the company’s employee data on their node

Transferring data from an applicant’s individual Holochain node to the company’s employee data on their node would require coordination and a defined process. Here’s a potential approach for achieving this transfer:

  1. Data Preparation: The applicant’s individual Holochain node would need to prepare the data for transfer to the company’s employee data. This might involve extracting the relevant information, formatting it according to the data structure required by the company’s employee data, and ensuring the data is complete and accurate.
  2. Consent and Authorization: The applicant would need to provide explicit consent and authorization for the transfer of their data to the company’s employee data. This ensures compliance with data privacy regulations and establishes a clear understanding between the applicant and the company regarding data usage and ownership.
  3. Secure Data Transmission: To transfer the data securely, both the applicant’s node and the company’s employee node would establish a secure connection using encryption and authentication mechanisms. This ensures that the data is protected during transmission and only accessible by authorized parties.
  4. Data Validation and Integration: Upon receiving the data, the company’s employee node would validate and process it to ensure its integrity and compatibility with the employee data structure. This might involve validating the data against predefined rules, checking for duplicates or errors, and integrating the transferred data into the employee’s existing data set.
  5. Verification and Confirmation: Once the data transfer and integration process is complete, the company’s employee node can provide verification or confirmation to the applicant’s node, indicating the successful transfer and incorporation of the data into the company’s employee data. This serves as an acknowledgment to the applicant that their data has been securely transferred and is now part of the company’s system.

It’s important to note that the specific implementation details would depend on the design and requirements of the Holochain application being used, as well as any applicable data protection regulations. Custom development and configuration would be required to establish the secure connection, validate data, and ensure compliance with privacy and security standards.