Protobuf Documentation

📝 Description

This module implements a Prolog logic interpreter (go-native) and its unification algorithm to evaluate logical expressions against the current state of the blockchain.

This distinctive module allows for the creation of advanced, goal-oriented queries and logical systems that can be applied to a wide range of use cases, while still maintaining the determinism and predictability of blockchain technology. It also features a collection of predefined, blockchain-specific predicates that can be used to access information about the state of the blockchain.

Concepts

Program

A program is a text that is parsed and compiled by the interpreter. A program is composed of a set of predicates, which are defined by the user and can be used to express the desired query logic.

Predicate

A predicate is a statement that describes a relationship between one or more variables or constants. A predicate consists of a name followed by zero or more arguments.

Rule & Fact

A rule is a statement that describes a relationship between one or more variables or constants, similar to a predicate. However, unlike a predicate, a rule also specifies one or more conditions that must be true in order for the relationship described by the rule to hold.

A rule has the following format:

head :- body.

The symbol :- is called the "if-then" operator, and it means that the relationship described in the head of the rule holds only if the conditions in the body are true.

For example:

grandfather(X,Y) :- father(X,Z), father(Z,Y). # X is the grandfather of Y if X is the father of Z and Z is the father of Y.

A fact is a special type of rule that has no body (with no :- and no conditions). A fact has the following format:

head.

For instance:

father(john, mary). # john is the father of mary.

Variable

A variable is a predicate argument that is used as a placeholder for a value. It can represent any type of data, such as numbers, strings, or lists.

Variables are denoted by a name that starts with an uppercase letter, for example X or Foo.

For instance:

father(X, mary). # ask for all X that are the father of mary.

Query

A query is a statement used to retrieve information from the blockchain. It can be sent against a program, but this is optional. The interpreter evaluates the query and returns the result to the caller. Queries can be submitted to a module using the Ask message.

Ask

The Ask message is used to submit a query to the module. It has the following format:

{
  string Program
  string Query
}

The Program field is optional. If it is not specified, the query is just evaluated against the current state of the blockchain. If it is specified, the query is evaluated against the program that is passed as an argument.

For instance:

{
  Program: "father(john, mary)."
  Query: "father(X, mary)."
}

Gives:

{
  "height": "7235",
  "gas_used": "9085",
  "answer": {
    "success": true,
    "has_more": false,
    "variables": [
      "X"
    ],
    "results": [
      {
        "substitutions": [
          {
            "variable": "X",
            "term": {
              "name": "john",
              "arguments": []
            }
          }
        ]
      }
    ]
  }
}

The logic module supports chain-specific predicates that can be used to query the state of the blockchain. For example, the chain_id predicate can be used to retrieve the chain ID of the current blockchain. Several other predicates are available, such as block_height, block_time... Please refer to the go documentation for the full list of available predicates.

For instance:

chain_id(X). # ask for the chain ID.

Response

The response is an object that contains the following fields:

• height: the height of the block at which the query was evaluated.
• gas_used: the amount of gas used to evaluate the query.
• answer: the result of the query. It is an object that contains the following fields:
  • success: a boolean that indicates whether the query was successful or not. Successful means that solutions were found, i.e. the query was satisfiable.
  • has_more: a boolean that indicates whether there are more results to be retrieved. It's just informative since no more results can be retrieved.
  • variables: an array of strings that contains the names of the variables that were used in the query.
  • results: an array of objects that contains the results of the query. Each result is an object that contains the following fields:
    • substitutions: an array of objects that contains the substitutions that were made to satisfy the query. A substitution is a set of variable-value pairs that is used to replace variables with constants. A substitution is the result of unification. A substitution is used to replace variables with constants when evaluating a rule.

Performance

The performance of the logic module is closely tied to the complexity of the query and the size of the program. To optimize performance, especially in a constrained environment like the blockchain, it is important to minimize the size of the program. Keep in mind that he module uses backtracking to search for solutions, making it most effective when used for queries that are satisfiable. Indeed, if the query is not satisfiable, the module will attempt to find a solution by backtracking and searching through possible solutions for an extended period before ultimately being canceled.

Gas

The Ask message incurs gas consumption, which is calculated as the sum of the gas used to evaluate each predicate during the query evaluation process. Each predicate has a fixed gas cost that is based on its complexity.

While querying the module does not require any fees, the use of gas serves as a mechanism to limit the size and complexity of the query, ensuring optimal performance and fairness.

Security

The logic module is a deterministic program that is executed in a sandboxed environment and does not have the ability to submit transactions or make changes to the blockchain's state. It is therefore safe to use.

To control the cpu and memory usage of the module, the module is limited by several different mechanisms:

• max_gas: the maximum amount of gas that can be used to evaluate a query.
• max_size: the maximum size of the program that can be evaluated.
• max_result_count: the maximum number of results that can be returned by a query.

Additional limitations are being considered for the future, such as restricting the number of variables that can be utilized within a query, or limiting the depth of the backtracking algorithm.

Table of Contents

• logic/v1beta/params.proto
  • Interpreter
  • Limits
  • Params
• logic/v1beta/genesis.proto
  • GenesisState
• logic/v1beta/types.proto
  • Answer
  • Result
  • Substitution
  • Term
• logic/v1beta/query.proto

  • QueryServiceAskRequest

  • QueryServiceAskResponse

  • QueryServiceParamsRequest

  • QueryServiceParamsResponse

  • QueryService

• logic/v1beta/tx.proto
  • MsgService
• Scalar Value Types

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logic/v1beta/params.proto

Interpreter

Interpreter defines the various parameters for the interpreter.

Field	Type	Label	Description
registered_predicates	string	repeated	registered_predicates specifies the list of registered predicates/operators, in the form of: <predicate_name>/<arity>. For instance: findall/3. If not specified, the default set of predicates/operators will be registered.
bootstrap	string		bootstrap specifies the initial program to run when booting the logic interpreter. If not specified, the default boot sequence will be executed.

Limits

Limits defines the limits of the logic module.

Field	Type	Label	Description
max_gas	string		max_gas specifies the maximum amount of computing power, measured in "gas," that is allowed to be consumed when executing a request by the interpreter. The interpreter calculates the gas consumption based on the number and type of operations that are executed, as well as, in some cases, the complexity of the processed data. nil value remove max gas limitation.
max_size	string		max_size specifies the maximum size, in bytes, that is accepted for a program. nil value remove size limitation.
max_result_count	string		max_result_count specifies the maximum number of results that can be requested for a query. nil value remove max result count limitation.

Params

Params defines all the configuration parameters of the "logic" module.

Field	Type	Label	Description
interpreter	Interpreter		Interpreter specifies the parameter for the logic interpreter.
limits	Limits		Limits defines the limits of the logic module. The limits are used to prevent the interpreter from running for too long. If the interpreter runs for too long, the execution will be aborted.

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logic/v1beta/genesis.proto

GenesisState

GenesisState defines the logic module's genesis state.

Field	Type	Label	Description
params	Params		The state parameters for the logic module.

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logic/v1beta/types.proto

Answer

Answer represents the answer to a logic query.

Field	Type	Label	Description
success	bool		result is the result of the query.
has_more	bool		has_more specifies if there are more solutions than the ones returned.
variables	string	repeated	variables represent all the variables in the query.
results	Result	repeated	results represent all the results of the query.

Result

Result represents the result of a query.

Field	Type	Label	Description
substitutions	Substitution	repeated	substitutions represent all the substitutions made to the variables in the query to obtain the answer.

Substitution

Substitution represents a substitution made to the variables in the query to obtain the answer.

Field	Type	Label	Description
variable	string		variable is the name of the variable.
term	Term		term is the term that the variable is substituted with.

Term

Term is the representation of a piece of data and can be a constant, a variable, or an atom.

Field	Type	Label	Description
name	string		name is the name of the term.
arguments	Term	repeated	arguments are the arguments of the term, which can be constants, variables, or atoms.

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logic/v1beta/query.proto

QueryServiceAskRequest

QueryServiceAskRequest is request type for the QueryService/Ask RPC method.

Field	Type	Label	Description
program	string		program is the logic program to be queried.
query	string		query is the query string to be executed.

QueryServiceAskResponse

QueryServiceAskResponse is response type for the QueryService/Ask RPC method.

Field	Type	Label	Description
height	uint64		height is the block height at which the query was executed.
gas_used	uint64		gas_used is the amount of gas used to execute the query.
answer	Answer		answer is the answer to the query.

QueryServiceParamsRequest

QueryServiceParamsRequest is request type for the QueryService/Params RPC method.

QueryServiceParamsResponse

QueryServiceParamsResponse is response type for the QueryService/Params RPC method.

Field	Type	Label	Description
params	Params		params holds all the parameters of this module.

QueryService

QueryService defines the gRPC querier service.

Method Name	Request Type	Response Type	Description	HTTP Verb	Endpoint
Params	QueryServiceParamsRequest	QueryServiceParamsResponse	Params queries all parameters for the logic module.	GET	/okp4/okp4d/logic/params
Ask	QueryServiceAskRequest	QueryServiceAskResponse	Ask executes a logic query and returns the solutions found. Since the query is without any side-effect, the query is not executed in the context of a transaction and no fee is charged for this, but the execution is constrained by the current limits configured in the module.	GET	/okp4/okp4d/logic/ask

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logic/v1beta/tx.proto

MsgService

MsgService defines the service for the logic module. Do nothing for now as the service is without any side effects.

Method Name	Request Type	Response Type	Description	HTTP Verb	Endpoint

Scalar Value Types

.proto Type	Notes	C++	Java	Python	Go	C#	PHP	Ruby
double		double	double	float	float64	double	float	Float
float		float	float	float	float32	float	float	Float
int32	Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint32 instead.	int32	int	int	int32	int	integer	Bignum or Fixnum (as required)
int64	Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint64 instead.	int64	long	int/long	int64	long	integer/string	Bignum
uint32	Uses variable-length encoding.	uint32	int	int/long	uint32	uint	integer	Bignum or Fixnum (as required)
uint64	Uses variable-length encoding.	uint64	long	int/long	uint64	ulong	integer/string	Bignum or Fixnum (as required)
sint32	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s.	int32	int	int	int32	int	integer	Bignum or Fixnum (as required)
sint64	Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s.	int64	long	int/long	int64	long	integer/string	Bignum
fixed32	Always four bytes. More efficient than uint32 if values are often greater than 2^28.	uint32	int	int	uint32	uint	integer	Bignum or Fixnum (as required)
fixed64	Always eight bytes. More efficient than uint64 if values are often greater than 2^56.	uint64	long	int/long	uint64	ulong	integer/string	Bignum
sfixed32	Always four bytes.	int32	int	int	int32	int	integer	Bignum or Fixnum (as required)
sfixed64	Always eight bytes.	int64	long	int/long	int64	long	integer/string	Bignum
bool		bool	boolean	boolean	bool	bool	boolean	TrueClass/FalseClass
string	A string must always contain UTF-8 encoded or 7-bit ASCII text.	string	String	str/unicode	string	string	string	String (UTF-8)
bytes	May contain any arbitrary sequence of bytes.	string	ByteString	str	[]byte	ByteString	string	String (ASCII-8BIT)