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Version: 0.1.4

Distributed Ledger Technology architecture modeling tutorial

This tutorial has appeared at the ACM / IEEE 27th International Conference on Model Driven Engineering Languages and Systems (MODELS) on September 22, 2024.

Metamodeling​

1. Simple example​

class FabricNetwork {
    contains Organization[1..*] organizations
    contains Channel[1..*] channels
}

class Organization {
    contains Host[1..*] hosts
}

class Host {
    contains Node[1..4] nodes
}

class Node.

class Channel {
    Node[1..*] peers
}

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2. Complete metamodel without derived features​

abstract class FabricNetwork {
    contains Organization[1..*] organizations
    contains Channel[1..*] channels
}

class KafkaFabricNetwork extends FabricNetwork.

class RaftFabricNetwork extends FabricNetwork.

class Organization {
    contains Host[1..*] hosts
}

class Host {
    contains Node[1..4] nodes
}

abstract class Node.

class OrderingNode extends Node {
    Channel[1..*] orders opposite orderedBy
}

class EndorsingNode extends Node {
    ChaincodeInstance[1..*] endorses opposite endorsedBy
}

class Channel {
    contains ChaincodeInstance[1..*] chaincodes
    OrderingNode[0..*] orderedBy opposite orders
}

class ChaincodeInstance {
    EndorsingNode[2..*] endorsedBy opposite endorses
}

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Partial model fragments​

3. Consistent partial model fragment​

KafkaFabricNetwork(network).
!exists(KafkaFabricNetwork::new).
!exists(RaftFabricNetwork::new).

default !channels(*, *).
channels(network, Ch1).
channels(network, Ch2).

!exists(Organization::new).
Organization(OrgA).
hosts(OrgA, HA1).
Organization(OrgB).
Organization(OrgC).

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4. Inconsistent partial model fragment​

KafkaFabricNetwork(network).
!exists(KafkaFabricNetwork::new).
!exists(RaftFabricNetwork::new).

!exists(Organization::new).
Organization(OrgA).
hosts(OrgA, HA1).
Organization(OrgB).
hosts(OrgB, HA1).
Organization(OrgC).

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Graph queries​

5. Simple constraint​

error channelInKafkaNetworkWithoutOrderer(c) <->
    channels(n, c),
    KafkaFabricNetwork(n),
    !orderedBy(c, _).

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6. Constraint with auxiliary predicate​

% Auxiliary predicate for invalidOrdererOrganization
pred ordererOrganization(o) <->
    Organization(o),
    hosts(o, h),
    nodes(h, n),
    OrderingNode(n).

error invalidOrdererOrganization(o) <->
    ordererOrganization(o),
    organizations(n, o),
    !KafkaFabricNetwork(n).

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7. Partial model inconsistent with the constraints​

RaftFabricNetwork(network).
!exists(KafkaFabricNetwork::new).
!exists(RaftFabricNetwork::new).

organizations(network, OrgA).
hosts(OrgA, HA).
nodes(HA, NA).
OrderingNode(NA).

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8. Definition of derived features​

% Auxiliary predicate for derived features
pred peerHelper(Channel c, Host h, Node n) <->
    orders(n, c),
    nodes(h, n)
;
    chaincodes(c, i),
    endorses(n, i),
    nodes(h, n).

pred peer(n, c) <-> peerHelper(c, _, n).

pred participatesIn(o, c) <->
    hosts(o, h),
    peerHelper(c, h, _).

pred collaboratesWith(Organization o1, Organization o2) <->
    o1 != o2,
    participatesIn(o1, c),
    participatesIn(o2, c).

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Generating consistent models​

9. Partial model fragment with derived features​

KafkaFabricNetwork(network).
!exists(Organization::new).
Organization(OrgA).
Organization(OrgB).
Organization(OrgC).

!collaboratesWith(OrgA, OrgB).
collaboratesWith(OrgA, OrgC).
collaboratesWith(OrgB, OrgC).

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10. Scope declaration to control model size​

scope node = 15..60,
  Node = 8..30,
  OrderingNode = 4..15,
  EndorsingNode = 4..15,
  Channel = 3..*,
  FabricNetwork = 1.

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Propagation rules​

11. Simple propagation rule​

propagation rule collaboratesWithSymmetric(Organization o1, Organization o2) <->
    collaboratesWith(o1, o2)
==>
    collaboratesWith(o2, o1).

propagation rule notCollaboratesWithSymmetric(Organization o1, Organization o2) <->
    !collaboratesWith(o1, o2)
==>
    !collaboratesWith(o2, o1).

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12. Propagation rules for negative pattern​

propagation rule cannotParticipateIn(Organization o1, Channel c) <->
    participatesIn(o2, c),
    !collaboratesWith(o1, o2),
    o1 != o2
==>
    !participatesIn(o1, c).

propagation rule cannotBePeerOf(Node n, Channel c) <->
    nodes(h, n),
    hosts(o, h),
    !participatesIn(o, c)
==>
    !peer(n, c).

% We don't need to know that n is an EndorsingNode to exdcute this rule.
propagation rule cannotEndorse(Node n, ChaincodeInstance i) <->
    chaincodes(c, i),
    !peer(n, c)
==>
    !endorses(n, i).

% We don't need to know that n is an OrderingNode to exdcute this rule.
propagation rule cannotOrder(Node n, Channel c) <->
    !peer(n, c)
==>
    !orders(n, c).

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13. Partial model fragment to illustrate reasoning​

KafkaFabricNetwork(network).
hosts(OrgA, HA).
nodes(HA, NA).
hosts(OrgB, HB).
nodes(HB, NB).
channels(network, Ch1).
chaincodes(Ch1, Ci1).
endorses(NA, Ci1).

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14. Complex propagation rule auxiliary predicates and modality​

shadow pred endorsesChaincode(EndorsingNode n, Channel c, ChaincodeInstance i) <->
    chaincodes(c, i),
    endorses(n, i).

shadow pred endorsesMultipleChaincodes(EndorsingNode n, Channel c) <->
    endorsesChaincode(n, c, i1),
    endorsesChaincode(n, c, i2),
    i1 != i2.

propagation rule mustEndorse(EndorsingNode n, ChaincodeInstance i) <->
    peer(n, c),
    !endorsesMultipleChaincodes(n, c),
    chaincodes(c, i),
    may endorses(n, i)
==>
    endorses(n, i).

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15. Partial model fragment to illustrate complex propagation​

KafkaFabricNetwork(network).
hosts(OrgA, HA).
nodes(HA, NA).
hosts(OrgB, HB).
nodes(HB, NB).
channels(network, Ch1).
chaincodes(Ch1, Ci1).

EndorsingNode(NA).
peer(NA, Ch1).
!chaincodes(Ch1, ChaincodeInstance::new).

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