Interfaces Module

---

This module defines the following types:

• IType
• ITerm
• IVar
• IConst
• ISubstitution
• IParser
• IPrettyPrinter
• ISubstrateTerm
• ISubstrateUpdateTerm
• ISubstrateQueryTerm
• ISubstrate
• IInfostrate
• IMailBox
• IRouter
• ISignatureProvider
• ILogicEngine
• IExecutor
• IParsingContext
• ISubstrateParser
• ISubstratePrettyPrinter
• ITranslatedExpr
• ITranslator

---

IType Type

Each IType implementation represents a type for AST elements. For instance infons, principals, integers, rules, evidence, ...

Methods

Modifiers	Return type	Method name	Method parameters	Description
	bool	IsSubtypeOf	IType	Returns true if this type can be seen as the typed passed as parameter

Properties

Return type	Property name	Description
string	Name	Short name for this type
string	FullName	Full name for this type
IType option	BaseType	Base type

---

ITerm Type

ITerm implementations are the AST elements. They encode everything from variables and constants to asInfon queries, rules, etc.

Methods

Modifiers	Return type	Method name	Method parameters	Description
	ITerm	Apply	ISubstitution	Returns a new ITerm which results from applying the given substitution
	ITerm	Normalize		Returns a new ITerm which is a normalized version of this one
	ISubstitution option	UnifyFrom	ISubstitution, ITerm	It tries to unify this ITerm with the given one, starting from the given substitution. If the unification is successful, a new substitution (which is a specialization of the given one) is returned. None is returned if unification fails
	ISubstitution option	Unify	ITerm	It tries to unify this ITerm with the given one. If unification is successful a substitution that guarantees syntactic equality is returned, otherwise None is returned

Properties

Return type	Property name	Description
IType	Type	The type of this AST element
IVar list	Vars	The free variables in this AST element
IVar list	BoundVars	The bound variables in this AST element

---

IVar Type

IVar is used to represent any AST element that is to be treated like a variable

Implemented Interfaces

• ITerm

Properties

Return type	Property name	Description
string	Name	Variable name, which is used as variable identifier

---

IConst Type

IConst is an interface that is implemented by all the AST nodes that represent ground values

Implemented Interfaces

• ITerm

Properties

Return type	Property name	Description
Object	Value	The value of this constant

---

ISubstitution Type

ISubstitution implementations model substitutions that map variables to AST elements (IVar --> ITerm). They are used as results of unification

Methods

Modifiers	Return type	Method name	Method parameters	Description
	ITerm	Apply	IVar	Applies this substitution to the given IVar
	ISubstitution	Extend	IVar, ITerm	Returns a new substitution that results from extending the current substitution so that it maps v to t and leaves the rest unchanged
	ISubstitution	ComposeWith	ISubstitution	Returns a new substitution that results from first applying s' and then applying the current Substitution
	bool	DomainContains	IVar	Returns true iff v is affected by this substitution
	ISubstitution	RestrictTo	IVar list	Returns a new substitution that results from restricting the current one to only modify the variables given in the list
	ISubstitution	Forget	IVar list	Returns a new substitution that results from forgetting the current mapping to the variables given in the list

Properties

Return type	Property name	Description
IVar list	Domain	Returns the vars affected by this substitution
bool	IsVariableRenaming	Returns true if this substitution only renames variables

---

IParser Type

IParser provides an interface for different parsers. All implementations of IParser process input strings and return ITerms

Methods

Modifiers	Return type	Method name	Method parameters	Description
	IType	ParseType	string	Parse an IType from the input string
	ITerm	ParseTerm	string	Parse an ITerm from the input string

---

IPrettyPrinter Type

IPrettyPrinter provides an interface to print ITerms back into different concrete syntaxes. An IPrettyPrinter implementation should be bound to an IParser implementation that can parse the output back

Methods

Modifiers	Return type	Method name	Method parameters	Description
	string	PrintType	IType	Returns a string representation for the given IType
	string	PrintTerm	ITerm	Returns a string representation for the given ITerm (infon, rule, etc.)

---

ISubstrateTerm Type

ISubstrateTerm implementations are AST elements which are related to a substrate. Each ISubstrateTerm has a Namespace, each ISubstrate understands a set of Namespaces.

Implemented Interfaces

• ITerm

Properties

Return type	Property name	Description
string	Namespace	Tha namespace for this ISubstrateTerm. This is used to locate an ISubstrate implementation that will understand this ISubstrateTerm

---

ISubstrateUpdateTerm Type

ISubstrateUpdateTerm implementations are substrate terms that perform updates (addition, modification, removal, changing parameters etc.) on a substrate. They are used in "apply" acctions

Implemented Interfaces

• ISubstrateTerm
• ITerm

---

ISubstrateQueryTerm Type

ISubstrateQueryTerm implementations are substrate terms that perform queries on a substrate. They are used in asInfon constructs

Implemented Interfaces

• ISubstrateTerm
• ITerm

---

ISubstrate Type

ISubstrate implementations give DKAL the ability to query and modify data sitting in various formats and representations (XML, arithmetics, SQL, etc.) Each substrate understand a set of namespaces, which are used to fetch the proper substrate when an ISubstrateTerm is found and needs to be executed

Methods

Modifiers	Return type	Method name	Method parameters	Description
	ISubstitution seq	Solve	ISubstrateQueryTerm seq, ISubstitution seq	Performs the given queries (which must have a namespace understood by this substrate) for each of the given input substitutions (partial results). Returns a sequence of resolved substitutions (more specialized than substs)
	bool	Update	ISubstrateUpdateTerm seq	Applies the given ISubstrateUpdateTerms (which must have a namespace understood by this substrate). Returns true upon success, false otherwise
	bool	AreConsistentUpdates	ISubstrateUpdateTerm seq	Given the ISubstrateUpdateTerms (which must have a namespace understood by this substrate) it returns true iff it is safe to apply them in parallel (e.g. no row is being deleted and added at the same time, etc.)
	IVar list	RequiredVars	ISubstrateQueryTerm	Given the ISubstrateQueryTerm (which must have a namespace understood by this substrate), it returns which of the query free variables must be instantiated before executing the query. For instance, an arithmetic calculator substrate may require all variables to be instantiated, except for the variable that gets the result (left-hand side can be free)

Properties

Return type	Property name	Description
HashSet<string>	Namespaces	Returns the set of namespaces that this ISubstrate implementation understands

---

IInfostrate Type

Provides an interface for a repository of knowledge in the form of infon ITerms

Methods

Modifiers	Return type	Method name	Method parameters	Description
	bool	Learn	ITerm	Adds the given infon ITerm to the infostrate
	bool	Forget	ITerm	Removes the given infon ITerm from the infostrate

Properties

Return type	Property name	Description
ITerm seq	Knowledge	Returns a sequence of knowledge from the infostrate

---

IMailBox Type

Provides an interface for a repository of incoming infon ITerms

Methods

Modifiers	Return type	Method name	Method parameters	Description
	unit	Add	ITerm, ITerm	Adds the given infon ITerm to the mailbox
	unit	Remove	ITerm, ITerm list option	Removes the given infon ITerm from the mailbox
	unit	Prune		Eliminates "old" messages, each mailbox decides how to implement this operation, which should be invoked at the end of each execution round
	ISubstitution seq	Matches	ITerm, ITerm, ISubstitution seq	Match an infon to messages in the mailbox. It returns a subset of (possibly specialized) substitutions.

---

IRouter Type

IRouter provides an interface for communication with the environment. Implementations of IRouter handle both incoming and outcoming messages

Methods

Modifiers	Return type	Method name	Method parameters	Description
	unit	Start		Must be called to initialize the router
	unit	Stop		Must be called after the router is no longer needed
	unit	Receive	ITerm -> ITerm -> unit
	unit	Send	ITerm, ITerm	Sends an infon ITerm to the target principal ITerm

Properties

Return type	Property name	Description
string	Me	Returns the current principal name
string list	Roster	Returns the names of the known principals

---

ISignatureProvider Type

ISignatureProvider provides an interface for implementations to construct and verify signed infons

Methods

Modifiers	Return type	Method name	Method parameters	Description
	int	ConstructSignature	ITerm, string	Construct a signature for the given ITerm
	bool	CheckSignature	ITerm, string, int	Checks if the given signature is correct

---

ILogicEngine Type

ILogicEngine provides an interface for logic reasoning engines that handle the infostrate

Methods

Modifiers	Return type	Method name	Method parameters	Description
	unit	Start		Must be called to initialize the engine
	unit	Stop		Must be called after the engine is no longer needed
	ISubstitution seq	Derive	ITerm, ISubstitution seq	Given an infon ITerm with (possibly) free variables and an initial sequence of substitutions it returns all those (possibly specialized) substitutions that make the infon hold
	ISubstitution seq	DeriveJustification	ITerm, ITerm, ISubstitution seq	Constructs evidence for the given infon ITerm that matches the given proofTemplate, if possible. Works under the given substitutions, returning more concrete ones (to instantiate the proofTemplate when successfull)
	ITerm option	CheckJustification	ITerm	Checks if the given evidence is a well-formed justification, if it succeeds it returns the infon that is justified by the evidence; it it does not suceed it returns None
	bool	Complete	ITerm	Learns that the knowledge learnt so far for a given relation (wrapped as an infon) is complete (closed)

Properties

Return type	Property name	Description
IInfostrate	Infostrate	The knowledge source for the logic engine
ISignatureProvider	SignatureProvider	The signature checking implementation for this logic engine

---

IExecutor Type

IExecutor provides an interface for the engine driver. IExecutor implementations are in charge of keeping a policy and apply all the rules as their conditions are triggered

Methods

Modifiers	Return type	Method name	Method parameters	Description
	unit	Start		Must be called to initialize the executor
	unit	Stop		Must be called when the executor is no longer needed
	bool	InstallRule	ITerm	Installs the given rule ITerm on the executor. The rule is followed from this point onwards. Returns false if the rule was already installed
	bool	UninstallRule	ITerm	Uninstalls the given rule ITerm on the executor. Returns true if the rule was not present
	unit	FixedPointCallback	unit -> unit
	unit	WakeUpCallback	unit -> unit
	unit	ActionCallback	ITerm -> unit
	unit	ReceiveCallback	ITerm -> ITerm -> unit
	unit	RoundStartCallback	unit -> unit

---

IParsingContext Type

IParsingContext provides an interface for contexts that keep information necessary during the parsing process such as variable types, macro definitions, etc.

Methods

Modifiers	Return type	Method name	Method parameters	Description
	bool	HasVariable	string	Returns true if there is a variable in the context with the given name
	IType	VariableType	string	For a variable name in the context, it returns its type
	unit	AddTypeRename	string, IType	Adds a type rename by giving a newTypeName to a given targetType
	IType	TypeFromName	string	Given a type fullname it returns the AST type for it
	bool	HasMacro	string	Returns true iff the contexts has a macro definition with the given name
	unit	AddMacro	string, IType, ISubstrateQueryTerm, IVar list	Given a macro name, a return type, a body and arguments, it incorporates these as a new macro in the context.
	IVar list	GetMacroArgs	string	Given a macro name in the context it returns the macro arguments
	IType	GetMacroRetType	string	Given a macro name in the context it returns the macro return type
	ITerm * ISubstrateQueryTerm	ApplyMacro	string, ITerm list	Given a macro name and concrete arguments, it returns a tuple (t, sqt) where t is the element that should be inlined (the macro return variable) and sqt is the macro body with the concrete arguments (which should be incorporated as an asInfon(sqt) somewhere before or after t is used)
	IVar	FreshVar	IType	Given a type it returns a fresh variable of that type

Properties

Return type	Property name	Description
string	Me	Name of the principal for which the policy is being parsed

---

ISubstrateParser Type

ISubstrateParser provides an interface for substrate parsers that interpret substrate queries and update terms

Methods

Modifiers	Return type	Method name	Method parameters	Description
	unit	SetParsingContext	IParsingContext	Sets the parsing context (that contains type information and macros among others) for this parser
	unit	SetNamespace	string	Sets the namespace to be used in all the ISubstrateTerms produced by this parser
	unit	SetSubstrate	ISubstrate	Sets the ISubstrate implementation that will be used to interpret the ISubstrateTerms produced by this parser. This ISubstrate may be used to obtain extra information during parsing (for instance, the SQL substrate parser uses a SQL ISubstrate implementation to get type information for the columns mentioned in the queries and updates)
	ISubstrateTerm	ParseTerm	string	It produces an ISubstrateTerm from the given string representation

---

ISubstratePrettyPrinter Type

ISubstratePrettyPrinter provides an interface to print substrate AST elements

Methods

Modifiers	Return type	Method name	Method parameters	Description
	string	PrintTerm	ISubstrateTerm	Returns a string representation for the given ISubstrateTerm

---

ITranslatedExpr Type

Wraps around a generic translated expression

Methods

Modifiers	Return type	Method name	Method parameters	Description
	Object	getUnderlyingExpr		Gets the underlying expression which is completely domain related

---

ITranslator Type

ITranslator provides a mechanism for translating ITerm elements to any other expression

Methods

Modifiers	Return type	Method name	Method parameters	Description
	ITranslatedExpr	translate	ITerm	Translates an ITerm to an ITranslatedExpr

---