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by Shaun Daley

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Inspiration

London’s antique water distribution network is infamous: it loses a quarter of the water supplied to London (spilt into the ground). Consequence: desalination, massive additional CO2 emissions, road congestion caused by too many emergency excavations and very high water prices for consumers. London’s case is severe but not atypical: most cities suffer from the same underlying infrastructure problem. Pipes and valves buried below busy urban streets are inherently difficult and expensive to maintain. Inaccessibility, lack of information, failure to efficiently process data and the high cost of each human intervention in legacy systems all compound to undermine efficient resource distribution.

Modern wireless networking offers the first crucial part in reducing the human time and cost of maintenance, and avoiding environmental damage: modern valves can be remotely (and even autonomously) operated to isolate components and pipe sections; modern flow sensors can transmit cross-section flow rates minute-by-minute. The remaining challenge is to log, model and process these resources on a city scale (London sized) with several hundred million components (pipe sections, valves, pumps, flow sensors, outlets, sources, etc) and the sparse, evolving relations between those components. Neo4j fits this bill perfectly.

To illustrate the domain, we’ll eliminate most complexity and focus on a single (but ubiquitous) problem.

Using the Design for Queryability modeling approach by Ian Robinson

1. Application/End-User Goals

As an engineer for a water utility

I want to know the accessible (remotely controllable, man-hole-accessible or excavation-accessible) valves for shutting off a set of components.

So that we can rapidly isolate a burst pipe, leaking valve or a set of components for replacement.

2. Questions To Ask of the Domain

What is the set of valves that must be closed to isolate the smallest possible part of the network including a set of components? What is the minimum set of network controllable (or manhole-accessible) valves that must be closed to isolate a set of components?

3. Identify Entities

  • Component (pipes, sources, outlets, pumps, flow sensors, etc)

  • Connection

  • Valve

4. Identify Relationships Between Entities

(:Component)  <- [:CONNECTS] - (:Connection) - [:CONNECTS] -> (:Component)
(:Valve)      - [:CLOSES]   -> (:Connection)

Valves are distinct objects with their own relationships e.g. IP address, API key, state information, whether they are manually closed clockwise or anti-clockwise (both valve closing directions exist and are widely prevalent in UK legacy water distribution infrastructure). For efficiency of querying, the nature of connections is duplicated in the relationship also:

(:Valve{access:'API'}) -> [:CLOSES] -> (:Connection) -> [:API_CONNECTS] -> (:Component)
(:Valve{access:'Manhole'}) -> [:CLOSES] -> (:Connection) -> [:MANHOLE_CONNECTS] -> (:Component)
(:Valve{access:'Excavation'}) -> [:CLOSES] -> (:Connection) -> [:EXCAV_CONNECTS] -> (:Component)

Candidate Data Model

CREATE
       (burstPipe:Component{name:"BurstPipe"}),
       (pipe1:Component),
       (pipe2:Component),
       (pipe3:Component),
       (pipe4:Component),
       (pipe5:Component),
       (pipe6:Component),
       (pipe7:Component),
       (pipe8:Component),
       (pipe9:Component),
       (pipe10:Component),
       (pipe11:Component),
       (connection1:Connection),
       (connection2:Connection),
       (connection3:Connection),
       (connection4:Connection),
       (connection5:Connection),
       (connection6:Connection),
       (connection7:Connection),
       (connection8:Connection),
       (connection9:Connection),
       (connection10:Connection),
       (connection11:Connection),
       (valve1:Valve {access:'API'}),
       (valve2:Valve {access:'Excavation'}),
       (valve3:Valve {access:'API'}),
       (valve4:Valve {access:'Manhole'}),
       (valve5:Valve {access:'API'}),
       (valve6:Valve {access:'API'}),
       (valve7:Valve {access:'API'}),
       (valve8:Valve {access:'API'}),
       (connection1)-[:API_CONNECTS]->(burstPipe),
       (connection1)-[:API_CONNECTS]->(pipe1),
       (connection2)-[:EXCAV_CONNECTS]->(burstPipe),
       (connection2)-[:EXCAV_CONNECTS]->(pipe2),
       (connection3)-[:CONNECTS]->(pipe2),
       (connection3)-[:CONNECTS]->(pipe3),
       (connection4)-[:API_CONNECTS]->(pipe2),
       (connection4)-[:API_CONNECTS]->(pipe4),
       (connection5)-[:MANHOLE_CONNECTS]->(pipe3),
       (connection5)-[:MANHOLE_CONNECTS]->(pipe5),
       (connection6)-[:API_CONNECTS]->(pipe3),
       (connection6)-[:API_CONNECTS]->(pipe6),
       (connection7)-[:CONNECTS]->(pipe5),
       (connection7)-[:CONNECTS]->(pipe7),
       (connection8)-[:CONNECTS]->(pipe5),
       (connection8)-[:CONNECTS]->(pipe8),
       (connection9)-[:API_CONNECTS]->(pipe5),
       (connection9)-[:API_CONNECTS]->(pipe9),
       (connection10)-[:API_CONNECTS]->(pipe7),
       (connection10)-[:API_CONNECTS]->(pipe10),
       (connection11)-[:API_CONNECTS]->(pipe8),
       (connection11)-[:API_CONNECTS]->(pipe11),
       (valve1)-[:CLOSES]->(connection1),
       (valve2)-[:CLOSES]->(connection2),
       (valve3)-[:CLOSES]->(connection4),
       (valve4)-[:CLOSES]->(connection5),
       (valve5)-[:CLOSES]->(connection6),
       (valve6)-[:CLOSES]->(connection9),
       (valve7)-[:CLOSES]->(connection10),
       (valve8)-[:CLOSES]->(connection11)
RETURN *
Loading graph...

Isolate the Burst Pipe Using Only Remote Calls to API-Accessible Valves

START burstPipe=node:node_auto_index(name='BurstPipe')
MATCH (burstPipe)-[:CONNECTS|EXCAV_CONNECTS|MANHOLE_CONNECTS*0..]-()-[:API_CONNECTS]- (h)-[:CLOSES]-(v{access:'API'})
RETURN v
Loading table...

Running queries, preparing the console!

Isolate the Burst Pipe Using Manhole-Accessible and API-Accessible Valves

START burstPipe=node:node_auto_index(name='BurstPipe')
MATCH (burstPipe)-[:CONNECTS|EXCAV_CONNECTS*0..]-()-[:MANHOLE_CONNECTS|API_CONNECTS]- (h)-[:CLOSES]-(v)
RETURN v
Loading table...

Running queries, preparing the console!

Isolate the Burst Pipe Using Any Existing Valves

START burstPipe=node:node_auto_index(name='BurstPipe')
MATCH (burstPipe)-[:CONNECTS*0..]-()-[:EXCAV_CONNECTS|MANHOLE_CONNECTS|API_CONNECTS]- (h)-[:CLOSES]-(v)
RETURN v
Loading table...

Running queries, preparing the console!

Extension

For real world application, there are some necessary modifications (e.g. modelling state information in relationships, such as whether a connection is presently closed or scheduled for opening/closing; limiting query depth and notifying of query failure in event of maximum query depth being reached).

In real world application, extending the above model, there is potential for adding greater value still:

  • estimating the marginal water savings from replacing any defined set of components

  • estimating the resilience of network water pressure to failure of specific pumps (both current and under hypothetical modifications to the network)

  • scheduling replacement or state-change of parts, and communicating this seamlessly (and automatically) in real time to all other parties that this might affect etc

This approach is more generic than it may initially seem. Many resource problems involve networks of distribution in which many components interact across sparse relationships (electricity generation and distribution, natural gas, sewage, district-piped heating); rapid and efficient querying on these relationships is necessary for efficient resource allocation and better environmental and cost outcomes.

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