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Symboleo Text Editor

An IDE for the formal contract specification Symboleo is created using Xtext DSL generator. For installating and using the IDE, please take a look at the installation guide.

What is Symboleo?

Symboleo is a formal contract specification language developed by Contract Specification and Modelling (CSM) Lab at Univeristy of Ottawa EECS department. The language aims to enable normative monitoring of smart contracts. Smart contracts are contracts that can monitor their performance (execution). They are a Cyber Physical System (CPS) that utilizes immutable ledgers (such as Distributed Ledger Technology (DLT) Platforms, a.k.a. blockchains).

For more information of Symboleo, please refer the preprint of our accepted paper for RE'20 conference here.

Current State

The current version of the text editor created by Xtext has implemented the syntax of Symboleo. It provides the capability to write Symboleo contract specifications more easily (autofill and syntax highlighting).

How to Use The IDE?

• Please follow the installation instructions provided in the INSTALL.md file to build the IDE.
• Assuming that the IDE is operational, open the runtime-Eclipse workspace using the steps provided in the installation guide.
• Create a New General Project (File | New | Project… | General | Project).
• Inside the project, create a new file with the .symboleo extension.
• System will prompt you to convert the project as a Xtext project, you should accept that for the Symboleo text editor to work.
• Now you can specify contracts in Symboleo and enjoy its syntax highlighting and autofill capabilities! (Note1: by default in Eclipse, you need to enter Ctrl + Space to use autofill). (Note2: the auto-fill feature might not suggest all the available options, as some of the grammar rules are implemented in a nested fashion).

How to Specify Contracts in Symboleo?

• A contract specification in Symboleo has two main sections: a Domain section and a Contract Body section. In the the domain section, you will be defining the data-model of the elements that are related to the (business) domain of the contract template you wish to specify. Some basic and ontological concepts (for more information on the ontology please consult our paper) are predefined in the language. Every other concept that is defined in the domain model is an extension of the pre-defined concepts. Note: Symboleo supports both time points and intervals. Since there is a one-to-one correspondance between events and time-points, and situations and time intervals; they can be used interchangeably.

Basic Conepts	Ontological Concepts
Enumeration	Event
String	Asset
Number	Role
Date	Contract
Boolean

• The contrct body has the following parts:

Contract Body Element	Description	Allowable Inputs
Contract Signature	contract template ID and contract parameters are defined	Contract ID & contract parameters and their type
Declarations	the parameters are bound to the variables which are defined based on the Domain Model of the contract	varisATypewhereatt_1:=param_1,...
Preconditions	the logical propositions that must be satisfied before a contract can be executed	logical proposition (Proposition)
Postconditions	the logical propositions that must be satisfied after a contract is executed	logical proposition (Proposition)
Obligations	obligations have a name, a trigger(optional), two roles, an antecedent and a consequent. the trigger when satisfied, creates an instance of the obligation, while satisfying its antecedent will bring it to an active state, i.e. the debtor of the obligation must satisfy the consequent.	oblName:trigger:Proposition-> O(debtor:Role ,creditor:Role,antecedent:Proposition,consequent:Proposition)
Powers	powers have a name, a trigger(optional), two roles, an antecedent and a consequent. the trigger when satisfied, creates an instance of the power, while satisfying its antecedent will bring it to an active state, i.e. the creditor of the power can satisfy the consequent which is usually about creating, suspending, resuming or terminating the obligations/contract.	powName:trigger:Proposition-> P(creditor:Role ,debtor:Role,antecedent:Proposition,consequent:Proposition)
Constraints	the logical propositions that must be always satisfied during the execution of the contract	logical proposition (Proposition)

• The sample Sales-of-Goods contract, which is provided in Symboleo-IDE/samples/MeatSaleContract.symboleo, illustrates how a simple contract can be specified in Symboleo.

Domain meatSaleDomain
  Seller isA Role with returnAddress: String, name: String;
  Buyer isA Role with warehouse: String;
  Currency isAn Enumeration(CAD, USD, EUR);
  MeatQuality isAn Enumeration(PRIME, AAA, AA, A);
  PerishableGood isAn Asset with quantity: Number, quality: MeatQuality;
  Meat isA PerishableGood;
  Delivered isAn Event with item: Meat, deliveryAddress: String, delDueDate: Date;
  Paid isAn Event with amount: Number, currency: Currency, from: Buyer, to: Seller, payDueDate: Date;
  PaidLate isAn Event with amount: Number, currency: Currency, from: Buyer, to: Seller;
  Disclosed isAn Event;
endDomain

Contract MeatSale (buyer : Buyer, seller : Seller, qnt : Number, qlt : MeatQuality, amt : Number, curr : Currency, payDueDate: Date, 
	delAdd : String, effDate : Date, delDueDateDays : Number, interestRate: Number
)

Declarations
  goods: Meat with quantity := qnt, quality := qlt;
  delivered: Delivered with item := goods, deliveryAddress := delAdd, delDueDate := Date.add(effDate, delDueDateDays, days);
  paidLate: PaidLate with amount := (1 + interestRate / 100) * amt, currency := curr, from := buyer, to := seller;
  paid: Paid with amount := amt, currency := curr, from := buyer, to := seller, payDueDate := payDueDate;
  disclosed: Disclosed;

Preconditions
  IsOwner(goods, seller);

Postconditions
  IsOwner(goods, buyer) and not(IsOwner(goods, seller));

Obligations
  delivery: Obligation(seller, buyer, true, WhappensBefore(delivered, delivered.delDueDate));
  payment: O(buyer, seller , true, WhappensBefore(paid, paid.payDueDate));
  latePayment: Happens(Violated(obligations.payment)) -> O(buyer, seller, true, Happens(paidLate));

//Surviving Obligations
//  so1 : Obligation(seller, buyer, true, not WhappensBefore(disclosed, Date.add(Activated(self), 6, months)));
//  so2 : Obligation(buyer, seller, true, not WhappensBefore(disclosed, Date.add(Activated(self), 6, months)));

Powers
  suspendDelivery : Happens(Violated(obligations.payment)) -> Power(seller, buyer, true, Suspended(obligations.delivery));
  resumeDelivery: HappensWithin(paidLate, Suspension(obligations.delivery)) -> P(buyer, seller, true, Resumed(obligations.delivery));
  terminateContract: Happens(Violated(obligations.delivery)) -> P(buyer, seller, true, Terminated(self));

Constraints
  not(IsEqual(buyer, seller));
  CannotBeAssigned(suspendDelivery);
  CannotBeAssigned(resumeDelivery);
  CannotBeAssigned(terminateContract);
  CannotBeAssigned(delivery);
  CannotBeAssigned(payment);
  CannotBeAssigned(latePayment);
  delivered.delDueDate < paid.payDueDate;

endContract

Examples

Example of three contracts with their Symboleo specifications and generated smart contracts are avaialbe in another repository.