Analysing River Systems with Time Series Data Using Path Queries in Graph Databases
Round 1
Reviewer 1 Report
The work of this manuscript would be better understood and its interestingness would be better appreciated if the authors could add a new section 2 to explain the motivating dataset and exclusively present your motivations underpinning your proposed work.
There are quite many English word typos and grammar errors. The authors should carefully read through their manuscript to correct them.
Author Response
Reviewer #1
Observation 1
The work of this manuscript would be better understood, and its interestingness would be better appreciated if the authors could add a new section 2 to explain the motivating dataset and exclusively present your motivations underpinning your proposed work.
Answer:
Thank you for the suggestion. In Section 1 (contributions) we have added two paragraphs explaining the real-world problem addressed in the paper, namely the water salinization problem in the Flanders region. We consider that the data set is described in detail in Section 7.
Observation 2
There are quite many English word typos and grammar errors. The authors should carefully read through their manuscript to correct them.
Answer:
Thank you, we have corrected several typos and errors (please see the response to Reviewer 2)).
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article describes a temporal graph structure that models transportation networks equipped with sensors. Compared to a static graph structure, its aim is to capture spatio-temporal evolutions more naturally. The authors introduce a high level query language to explore this spatio-temporal graph, with a system where high level spatio-temporal queries are kept simple, but are executed through a tranlation in a rawer graph language.
The authors describe their contribution as two-fold : the representation of transportation networks equipped with sensors with a spatio-temporal graph structure, and the querying of such databases with a high-level query language. apart from these two points, the article gives the description of different types of paths that can be of interest in a transportation network, and how such paths are characterized in the graph structure. In particular, the authors give the definition of flow paths in this setting, flow paths being general structures that can capture phenomena that flow forward or backward in the network.
The article is relatively long and contains 8 sections. apart from the introduction (section 1), recension of related works (section 2), use case (section 7) and conclusion (section 8), there is one section dedicated to formal definitions that are used throughout the paper (section 3), and then three sections dedicated to the core methodology, with a description of the spatio-temporal graph (section 4), of the paths that can be queried in this structure (section 5), and of how the querying language is structured and how queries are treated (with algorithms in pseudo-code) (section 6).
The relevance of a spatio-temporal graph to model and explore transportation networks is well-argumented, and the authors give examples of complex structures that can be better captured. The use of a high level language with relatively simple queries is also very useful. Overall, the paper is very well-written ; its length is explained by the fact that the authors introduce several complex definitions and methods, and take time to explain each one in a very detailed manner, to make it more understandable.
In found section 6 to be the hardest to understand. Explaining the pseudo-code by describing how it computes solutions for a concrete example is a commendable idea, but following the flow of the example is difficult. Maybe indenting the text at pp.18-19 would facilitate the reading.
I have a few remarks about notations and clarity in sections 3 and 4:
Definition 1 and the comments that precise it do not really explain how an object node and an attribute node really differ (apart from the different connection constraints). The difference is immediatly understandable when one reads Definition 2, but it could be useful to state it before, without giving more detail (as the explanations and example in Section 4 are very clear and need not be modified or displaced).
p.9-15: There is some confusion regarding the use of the notations n_a, n_v, a and v. At some point, the authors use n_a and n_v to indicate nodes, and v to indicate a value, but then they write ‘the attribute node a’, and ‘the attribute node v’, so the authors should clearly write what objects noted a or v can be.
Definition 3 is also confusing and not completely rigorously written ; keeping the notations above, the bullet point starting with ‘T is an interval such that’ should begin with :
T is an interval such that, for all i, there exists a \in N_a, v \in N_v, with a=n_a{s_i} and v=n_v{a}, such that…
(the notations at the end of p.9 imply that v{a{s_i}} is a quantity and not a logical proposition).
The same remark can be done for the third bullet point of Definition 4, where both notations v and n_v are used for the same object (a node). Additionnally, in Definition 4, T is introduced as a list of interval and is then written as an union. It would be more rigorous to write T=(T_i)_{i=1,..,k-1} is a list of intervals … and then
T_i=v_{i}.interval \cap v_{i+1}.interval (which would be coherent with Example 2 where T is written as a list).
In Definition 5 and Definition 6, it is also not clear whether T is a list or a union of intervals.
The English language is very good in general, with very good grammar overall. There are however several mistakes or awkward sentences in the first pages of the paper. Here is a list of mistakes or language suggestions, as well as a few typos:
p.1 help to keep → help keep
p.1 the consequence of unexpected events → the consequences of unexpected events
p.1 for various application areas → for various applications OR in various application areas
p.2 the river system is denoted a transportation network → the river system is called a transportation network
p.2 we will denote this networks […] as tranformation networks → we will call these networks […] transportation networks
Overall, there are several instances in the article where the use of the verb denote sounds improper. In these instances, it may be replaces by either call, or note.
p.2 nodes an edges → nodes and edges
p.2 were all measurements → where all measurements
p.2 at a certain time instant → at a given time OR at a given date
p.2 keeping track of the topology of the network, for example, of the time periods when a sensor was working → keeping track of the topology of the network, including, for example, the time periods when a sensor was working
p.2 temporal graphs allows → temporal graphs allow
p.2 have a more limited semantics → have more limited semantics
p.3 that can be help professionals → that can help professionals
p.3 we discuss and the river analysis scenario → we discuss the river analysis scenario (OR some words are missing)
p.3 we present and discuss in detail our use case → we present and discuss our use case in detail
p.4 This is one of the approaches […] informed decision making : this sentence is difficult to understand and should be reformulated
p.4 to a great extends → to a great extent
p.4 the socio-economical status → the socio-economical status of the region / of the area
p.5 a high-level query langage, denoted Cypher → a high-level query langage, called Cypher
p.5 In transportation networks, time-series data that are produced by sensors → In transportation networks, time-series data are produced by sensors
p.6 adding libraries […] that extends → adding libraries […] that extend
p.12 composed of sensor nodes such for every pair → composed of sensor nodes such that for every pair
p.17 the number of sensors in the path nbrOfSensors) : the opening parenthesis is missing
Author Response
Reviewer #2
The article describes a temporal graph structure that models transportation networks equipped with sensors. Compared to a static graph structure, its aim is to capture spatio-temporal evolutions more naturally. The authors introduce a high level query language to explore this spatio-temporal graph, with a system where high level spatio-temporal queries are kept simple, but are executed through a tranlation in a rawer graph language. The authors describe their contribution as two-fold : the representation of transportation networks equipped with sensors with a spatio-temporal graph structure, and the querying of such databases with a high-level query language. apart from these two points, the article gives the description of different types of paths that can be of interest in a transportation network, and how such
paths are characterized in the graph structure. In particular, the authors give the definition of flow paths in this setting, flow paths being general structures that can capture phenomena that flow forward or backward in the network.
The article is relatively long and contains 8 sections. apart from the introduction (section 1), recension of related works (section 2), use case (section 7) and conclusion (section 8), there is one section dedicated to formal definitions that are used throughout the paper (section 3), and then three sections dedicated to the core methodology, with a description of the spatio-temporal graph (section 4), of the paths that can be queried in this structure (section 5), and of how the querying language is structured and how queries are treated (with algorithms in pseudo-code) (section 6).
The relevance of a spatio-temporal graph to model and explore transportation networks is well-argumented, and the authors give examples of complex structures that can be better captured. The
use of a high level language with relatively simple queries is also very useful. Overall, the paper is very well-written; its length is explained by the fact that the authors introduce several complex definitions and methods, and take time to explain each one in a very detailed manner, to make it more understandable.
Observation 1
I found section 6 to be the hardest to understand. Explaining the pseudo-code by describing how it computes solutions for a concrete example is a commendable idea, but following the flow of
the example is difficult. Maybe indenting the text at pp.18-19 would facilitate the reading.
Answer:
Thank you for the suggestion. To make following the example easier, we added the line numbers to the algorithm and reference, in the text, each step to a line. We believe it clearer now.
Observation 2
I have a few remarks about notations and clarity in sections 3 and 4:
Definition 1 and the comments that precise it do not really explain how an object node and an attribute node really differ (apart from the different connection constraints). The difference is immediately understandable when one reads Definition 2, but it could be useful to state it before, without giving more detail (as the explanations and example in Section 4 are very clear and need not be modified or displaced).
Answer:
Thank you, we have added a paragraph after Definition 1 to clarify this.
Observation 3
p.9-15: There is some confusion regarding the use of the notations n_a, n_v, a and v. At some point, the authors use n_a and n_v to indicate nodes, and v to indicate a value, but then they write ‘the attribute node a’, and ‘the attribute node v’, so the authors should clearly write what objects noted a or v can be.
Answer:
Thank you for this observation. We have dropped notation n_o, n_a and n_v to indicate particular nodes, and replaced it by o,a,v respectively. The set of nodes are still denoted as N_o, N_a, N_v.
Observation 4
Definition 3 is also confusing and not completely rigorously written ; keeping the notations above, the bullet point starting with ‘T is an interval such that’ should begin with :T is an interval such that, for all i, there exists a \in N_a, v \in N_v, with a=n_a{s_i} and v=n_v{a}, such that… (the notations at the end of p.9 imply that v{a{s_i}} is a quantity and not a logical proposition).
Answer:
We have changed the definition as requested. In addition, to avoid confusion with subscripts, in the second bullet, x_i is changed for x_j (to distinguish it from the i of s_i).
Observation 5
The same remark can be done for the third bullet point of Definition 4, where both notations v and n_v are used for the same object (a node). Additionally, in Definition 4, T is introduced as a list of interval and is then written as an union. It would be more rigorous to write T=(T_i)_{i=1,..,k-1} is a list of intervals … and then T_i=v_{i}.interval \cap v_{i+1}.interval (which would be coherent with Example 2 where T is written as a list). In Definition 5 and Definition 6, it is also not clear whether T is a list or a union of intervals.
Answer:
Thank you, we have changed the definition as requested.
Observation 6
The English language is very good in general, with very good grammar overall. There are however several mistakes or awkward sentences in the first pages of the paper. Here is a list of mistakes or language suggestions, as well as a few typos:
Answer: We thank the reviewer for the detailed list below, and we indicate the corrections made.
p.1 help to keep → help keep Done
p.1 the consequence of unexpected events → the consequences of unexpected events Done
p.1 for various application areas → for various applications OR in various application areas Done
p.2 the river system is denoted a transportation network → the river system is called a transportation network. Done
p.2 we will denote this networks […] as tranformation networks → we will call these networks […] transportation networks Done
Overall, there are several instances in the article where the use of the verb denote sounds improper. In these instances, it may be replaces by either call, or note. Done
p.2 nodes an edges → nodes and edges Done
p.2 were all measurements → where all measurements Done
p.2 at a certain time instant → at a given time OR at a given date Done
p.2 keeping track of the topology of the network, for example, of the time periods when a sensor was working → keeping track of the topology of the network, including, for example, the time periods when a sensor was working Done
p.2 temporal graphs allows → temporal graphs allow Done
p.2 have a more limited semantics → have more limited semantics Done
p.3 that can be help professionals → that can help professionals Done
p.3 we discuss and the river analysis scenario → we discuss the river analysis scenario (OR some words are missing). Done
p.3 we present and discuss in detail our use case → we present and discuss our use case in detail Done
p.4 This is one of the approaches […] informed decision making : this sentence is difficult to understand and should be reformulated Done
p.4 to a great extends → to a great extent Done
p.4 the socio-economical status → the socio-economical status of the region / of the area Done
p.5 a high-level query langage, denoted Cypher → a high-level query langage, called Cypher Done
p.5 In transportation networks, time-series data that are produced by sensors → In transportation networks, time-series data are produced by sensors Done
p.6 adding libraries […] that extends → adding libraries […] that extend Done
p.12 composed of sensor nodes such for every pair → composed of sensor nodes such that for every pair Done
p.17 the number of sensors in the path nbrOfSensors) : the opening parenthesis is missing Done
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors have discussed about the path queries for river system. Overall, this paper is well organized, results are clearly articulated, and workflow is demonstrated with charts and examples.
Author Response
Reviewer #3
The authors have discussed about the path queries for river system. Overall, this paper is well organized, results are clearly articulated, and workflow is demonstrated with charts and examples.
Observation 1
Answer:
Thank you very much for these considerations.
Author Response File: Author Response.pdf
Reviewer 4 Report
This paper will benefit from a comprehensive review of grammar and spelling. Some of the issues found are included in the attached paper.
Comments for author File: Comments.pdf
Author Response
Observation 1
This paper will benefit from a comprehensive review of grammar and spelling. Some of the issues found are included in the attached paper.
peer-review-26349178.v1.pdf (/user/review/displayFile/35215135/FaRLbA0I?file=review&report=26349178)
Answer:
We thank the reviewer for the detailed document. We have addressed the observations.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am satisfied with the revision.
