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The VisTG Framework for
Network Visualisation
M. Martin Taylor (Secretary, IST-059/RTG-025)
Martin Taylor Consulting
[email protected]
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Why create a “Framework”?
Why is IST-059/RTG-025 concerned with the task of
developing a framework?
• If I have only a hammer, every job seems to require nails.
• If I need to fasten something, how do I know hammers exist?
• If I need something fastened and I know the tools exist, do I glue,
screw, staple, or nail?
•“I” would want a Framework that categorized fastening jobs in terms
of what tools were best for those jobs, and categorized tools in terms
of what kinds of fastening jobs they did best.
?
Based
Report
on report
to IST-063/RWS-010
to IST-063/RWS-010
by the IST-059/RTG-025
by the IST-059/RTG-025
Working
Working
Group Group
on Framework
on Framework
for Network
for Network
Visualisation
Visualisation
Why a Framework for network visualisation?
• Numerous ad-hoc examples of network representations have been created for
specific applications, some of them very good for their purpose.
• It is usually not clear how the insights that led to particularly effective
representations can be generalized to new situations.
• A good Framework should help identify the conditions for which different insights
are helpful.
• Users need to see different aspects of network structure and functioning in support
of their real-world task, and some of those aspects are not well served by extant
display techniques.
•Users usually choose to see those aspects for which effective display techniques are
available (they are given only a hammer!).
• A good Framework may help inspire research on new modes of display for different
kinds of network properties.
The Framework should support users with ad-hoc needs, and should
support system designers and researchers by highlighting aspects of
network properties that are poorly supported by existing technology.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Discussion plan for the presentation:
Framework for Network Visualisation
•Ancestor frameworks (VisTG Reference Model, RM-Vis
Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Why develop a Framework for Network Visualisation?
•IST-059 considered that the very concept of a real world network is illdefined. A network is more than a graph that can be described in a matrix,
even a matrix of N dimensions.
•Brilliant displays for many tasks involving networks have been devised, but
• IST-059 knew of no way the tasks and the networks and their contexts can
be consistently described, which makes it hard to link user requirements with
potentially useful tools or applications.
•Consistent description of tasks, networks, and display types might help in
designing displays useful for new problems.
The IST-059 Framework incorporates description,
function, and a process for using it in support of
users, researchers, and designers.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
How to develop a Framework for Network Visualisation?
The IST-059 Framework was developed in parallel with a Survey of
existing applications and tools for network visualisation.
The first requirement was to consider how to describe the important
attributes of
•User needs and capabilities
•Displayable properties of networks
•Display and interaction techniques
Only when these and related characteristics had been adequately
described could the process of using the Framework be designed.
A major aspect of the Framework is its use as a front-end to the Survey.
They must use compatible descriptions of what is needed and available.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
What is a
“Framework” for Network Visualisation?
•A way of categorizing and describing user needs, display
technologies, and network properties
• A help to users in assessing the nature of their requirements
• A guide to users in choosing a visualisation system suitable for
their application need.
• A guide to developers and researchers regarding unmet needs.
• An interface that connects a network-related task requirement
with the available display technologies
• An interface that connects the available display technologies
with computed network properties
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
C2 Network Visualisation Approaches
(From Vernik-Bouchard Presentation
at the IST-063/RWS-010 Workshop,
Copenhagen October 2006)
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
A Framework for Network Visualisation
The User’s Problem: How to coordinate
•One or more users want to solve some real-world difficulty that in some way
involves a network.
•The real-world data are abstracted into computer data that can be construed as
a network.
•Algorithms abstract both local and global properties of the network that might
be useful for the user’s real-world task.
• Properties of the network likely to be useful are displayed.
•The display helps the user or users to visualise the state of the real world in
which the difficulty exists.
Framework
•A Framework for network visualisation should tie together these elements in a
coherent way, relating task to display, and display to network properties.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
The Framework Concept
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
The Framework Concept
Survey
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
The form of a
Framework for Network Visualisation
A Framework for network visualisation should include:
• A structured approach to describing user needs
• A structured set of displayable properties of networks
• A structured way of describing display techniques
•A structured was of describing display interactions
• A process to help the user match needs to displayable
properties using the appropriate display techniques.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework roots: Visualisation Reference Models
•VisTG Reference Model
•A functional model developed initially by predecessor groups of
IST-059/RTG-025 and reported in the HAT Report
•User’s purposes determine the representation characteristics
•Separate interaction loop levels for primary tasks, algorithms and
engines, and interface
•RM-Vis Reference Model
•A descriptive model developed initially by a working group of The
Technical Co-operation Programme (TTCP) C3I AG-3
•Separable dimensions of description for application domain,
content to be displayed, and display approaches
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
The VisTG Reference Model
The VisTG Reference Model
has 3 loops, the outer acting
through the inner:
(1) The user understanding
and acting on the data in the
dataspace, which involves...
(2) The user visualising the data
provided by and massaged by
the analytic and presentation
Engines, under the control of
the user, who works through...
(3) The Input-Output devices
that interact with the user’s
sensors and musculature.
But we assume that the user “really” wants to influence the outer world!
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
RM-Vis Reference Model developed by TTCP C31 AG-3
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework for Network Visualisation
Discussion plan:
• Nature of a Framework, and Ancestor frameworks (VisTG
Reference Model, RM-Vis Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
VisTG Framework: Categorizing user tasks
We consider four distinct modes of perception. They suggest approaches
to information display, and can help categorize user tasks.
Perceptual Modes
1. Controlling/Monitoring: Keeping track of a changing
situation and possibly acting to alter it.
2. Searching: Looking for something immediately wanted
3. Exploring: Building understanding of slowly varying aspects
that could be useful for later search or control.
4. Alerting: Noting that a prespecified condition has occurred in a
datastream or exists within a large dataspace. Alerting is usually
an automated process.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Perceptual mode implications for display
The four modes often have implications for display: e.g. in an
anti-terrorist scenario
1.
Exploring involves the discovery of networks, and might benefit from
a fisheye display of the portions of the network so far discovered.
2.
Monitoring implies continuing observation of network changes and
traffic dynamics, and requires the ability to dive into detail.
3.
Searching concerns the attributes of specific nodes, to discover their
potentialities when matched with those of linked nodes, and hence
requires both wide range and closely focused display representations.
4.
Alerting is a programmed background activity that suggests the
requirement to display relevant aspects of the network in context,
when any of the prespecified patterns is detected.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework for Network Visualisation
Discussion plan:
• Nature of a Framework, and Ancestor frameworks (VisTG
Reference Model, RM-Vis Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework roots: Network properties
• Network types:
Point-to-point,
broadcast, striped, stigmergic, fuzzy or crisp
• Mathematical relations and functions in abstract networks
Many
important representable properties (e.g. SNA)
• Dynamical properties of real networks (e.g. Feedback loops)
• Transformational properties of nodes and links of real networks
Inputs
may be of different nature to outputs
• Embedding fields of real networks and of displays
Determine
and constrain potentialities of the network
• Data Source: static or streaming, and other properties
Is
the network changing while the user watches?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Network Types
•Point to point: The classic network. Nodes are defined and each node is or is not
linked to each other node by a link with some “weight” and structure.
Striped or Coloured: Nodes of type A can be linked only to nodes of type B
and vice-versa (e.g. humans and malaria-carrying mosquitoes).
•Broadcast: A transmitting node cannot know which of many eligible receiving
nodes may receive the traffic (e.g. airborne infection).
Ephemeral: Traffic not received when transmitted is lost.
Stigmergic: “Traffic” is left in the environment and may be received at an
indeterminate later time by an indeterminate number of receivers (e.g. ruts
that tend to guide later traffic, etc., or the clues to a crime left by the criminal
that may be read by a detective.)
•Fuzzy: Nodes and/or links are not well defined. Places may be more or less nodelike, and indefinitely linked to other nodes. The membership of an element in class
“node” or “link” may depend on the user’s purpose.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Fuzzy Nodes and Links
Fuzzy link membership should not be confused with link weight. Here’s a simple example
1
2
Original situation
A
Road between two towns
A Farmhouse is built near the road
Farm
B
A
A and B is a link
B
Is the road between A and B a
link? Yes, Pretty much. Is the
farm a node? Hardly.
3
More facilities are built
to service travellers
4
Farm
A
Gas
Hotel
B
Is the building cluster a node?
Somewhat, but not really. Is the
road between A and B a link or a
two-link path? A bit of each!
A
The cluster becomes a new town
X
B
Road between A and B is no longer a
link though it remains a path. Roads A-X
and B-X are links, and the expanded
cluster at X has clearly become a node.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Varieties of Link “Strength” – 1: Basic
In many displays of networks, “strong” links are shown more vividly than
are “weak” links. However, links have several independent parameters
that might be called “strength”
• Traffic-related
 Utilization — How much traffic is the link carrying?
 Capacity — How much traffic could the link sustain?
 Availability — What is the probability the link is open for traffic?
• Coherence
or Similarity
How tight is the relationship between the terminal nodes? (sibling is
tighter than second cousin; “see” is more closely related to”view” than
to “grow”)
• Fuzzy
membership — How much like a link is the connection?
How should these different kinds of link strength or
weight be distinguished in displays?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Varieties of Link “Strength” – 2: Complexity
A link may be simple, carrying one kind of traffic or representing one relationship, but
what seems to be a single link might actually be a bundle of elementary links of
different kinds. To view the network this way is different from viewing it as a layered
set of networks of different character.
For example, person A might at the same time
• be the father of person B,
• lend money to B,
• enjoy B’s company,
• telephone B frequently.
The complexity of a link bundle implies that the nodes it links are themselves complex,
each perhaps including a whole processing network that interconnects the elementary
links of the bundle. This is certainly true if a subnet has been compressed and must be
represented as a single node.
How should a “bundle” link be distinguished in displays? Is the
number of elementary links another dimension of link “strength”?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Transformational properties of nodes and links
In an abstract mathematical network, a node may be only a place where
traffic enters and is distributed to outgoing links.
In a real network, the nature of the traffic and its timing are determined by
processes that occur in the node and in the links.
Example: a person (a node) may receive messages from a variety of
sources over a period of time, may interpret the messages, and may take
action that affects other people, but not by sending messages.
•Point-to-point gossip about the evil effects of immunization may
cause a parent not to immunize a child, who then catches and
propagates a serious disease;
•Public broadcast messages may induce sufficient people to get
immunized that a potential pandemic is avoided.
The network in this example contains both broadcast and point-to-point
elements, the links are fuzzy, and the nodes significantly transform their inputs
in generating their outputs. How might all this be displayed?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Mathematical Properties
Most of the mathematical properties of networks have been developed in
connection with crisp point-to-point networks. A few examples:
•Network topology: random, scale-free, tree.
•Centrality: distribution of linkage degree over the nodes
•Directivity: Whether links are unidirectional or two-way
•Cyclicity: Can traffic go from A through other nodes and back to A?
•Diameter: The longest geodesic between any pair of nodes
• etc…..
The mathematical properties of fuzzy networks are less well developed,
but should reduce to those of crisp networks in the limit of binary
membership functions (only zero or unity allowed).
Mathematical properties often are important in interpreting the implications of
network structure in the real world, and should be displayed when needed. How?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework for Network Visualisation
Discussion plan:
• Nature of a Framework, and Ancestor frameworks (VisTG
Reference Model, RM-Vis Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Real Networks
Are not mathematical abstractions.
They are messy.
They are embedded in a complicated environment
They are not well-defined or completely known
They are what real users have to deal with.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Embedding fields of real networks – 1
•A network in the real world consists of physical or conceptual entities connected by
relationships that may be
physically embodied (e.g. roads, wires) or
purely conceptual (family tree, social influence, etc.)
•The network is embedded in a physical or conceptual substrate, but what determines
the relevant “embedding field” is the set of contextual attributes in which changes
make a difference to the network from the viewpoint of the user and for the user’s
current purpose. The effective embedding field can be thought of as the currently
relevant context.
Left: Road network in embedding
field of map showing directions,
distances, and landscape features.
Right: Subway network with
embedding topology of river and
rail lines.
Whatever is to be displayed, it will be better understood if it is shown in a
relevant context, and without irrelevant context. Networks are no different.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Embedding fields of real networks – 2
Networks are often displayed along with some aspect of
their embedding field to supply context.
But not always:
Two representations of part of the Internet.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Embedding fields of real networks – 3
The embedding field for a network may or may not be another network
•e.g. for a contagious disease, the network of infections is embedded
in the network of social contacts, but for an airborne disease or one
with an insect vector it is not.
Networks can inherit properties from their embedding fields
•e.g. location for a geographic embedding field, potentially
infectious contacts for a social contact network embedding field.
The embedding field constrains the properties of the embedded network,
but new attributes can be developed
•e.g. contacts are limited to those of the embedding social network,
but contact type – casual, intimate, telephonic, etc. – may be
attributes of the network of interest.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Embedding fields and network display
•Embedding fields are the context in which the network exists.
•Not all aspects of the context are relevant to the user’s task.
•Not only the network, but also the display medium can be
considered as a hierarchy of embedding fields, the root of which is,
say, the set of pixels of the display screen, intermediate levels might
be 2-D and then 3-D spaces containing objects, while the leaves
might consist of the coloured lines and objects used to show the
network attributes of concern.
•The immediately ancestral embedding field for the display of the
network may well be the appropriate environment in which to
display the user-relevant contextual embedding field of the network.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework for Network Visualisation
Discussion plan:
• Nature of a Framework, and Ancestor frameworks (VisTG
Reference Model, RM-Vis Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Categorizing Data Types
Six Descriptive Dimensions
from the Final Report of IST-013/RTG-002 (The HAT Report)
Acquisition
Streamed
Sporadic
Analogue
Regular
symbolic
Single
Multiple
Values
Nonlinguistic
linguistic
Nonlinguistic
Located
symbolic (non-linguistic)
Categoric
non-symbolic (non(fuzzy)
linguistic)
Labelled
User-structured
Externally imposed
Identification
Categoric
(crisp)
nonsymbolic
User-selected
interactive
Choice
vector
linguistic
Static
Sources
scalar
Relations
Source-structured
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Categorizing Display Techniques
Four Descriptive Dimensions
from the Final Report of IST-013/RTG-002 (The HAT Report)
Display Timing
Data Selection
Data Placement
Static picture
Dynamic variation
User-selected
Algorithmically selected
Located
Labelled
Analogue
Data Values
Categoric
scalar
vector
linguistic
symbolic
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Dynamic Properties of real networks
Network traffic changes over time, and networks themselves change.
If a network contains cycles, as most do, the traffic can vary regularly or
chaotically.
The passage of traffic can alter the network stigmergically
•e.g., in an infection network, the structure of the network changes
when a node (person) moves from susceptible to infective to immune
(or dead).
Cycles are not possible in an infection network if persons become
immune after being infected, even though the static structure of the
network and its embedding field suggest that cycles should exist.
Epidemic pulses must come from elsewhere – a larger network.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Interaction modes
The display may be for a single user or for multiple users
1.
Interactive: A single user may interact directly with the display
2.
Coordinated: Multiple users cannot interact freely with the display, but can
work together to Coordinate their interactions with one or more displays.
Coordination may use the displays or may use communication side-channels.
3.
Mediated: Single or multiple users may use a Mediated interaction with the
display, in which an operator manipulates the display for viewing by the end
user(s). Briefing is usually done by Mediated interaction with multiple endusers; senior officers usually interact with their displays as single end-users
mediated by an operator.
4.
Passive: In passive viewing, the user has no influence on the content or
manner of the display. Any number of users can view passively a display
such as in a book or on a Web site.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Interaction modes – 2
Interaction Modes affect which perceptual modes are
more likely to be used. (Table from draft Final Report of IST-059/RTG-025)
Table AD.7 Perceptual Modes most likely to be used in difference circumstances
Single end-user
Interactive
Coordinated
All Modes
N/A
Multiple Users
viewing
simul taneously
N/A
Multiple users
viewing separately
N/A
Monit or,
Explo re, Search,
Alert
Monit or,
Explo re, Search,
Alert
Mediated
Explo re,
Search
Passive
Explo re
Explo re
Explo re
N/A
Explo re
Almost all displays presented in demonstration and all presented in books
are viewed passively, and can be used mainly in Explore mode for
investigating network structure or historical dynamic behaviour.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Interaction modes – Display Implications
Interaction Modes affect the need for formal display syntax
In language, the syntax of conversational interaction is less formal than that
of a spoken lecture, which in turn is simpler than the syntax of written text,
because in conversational interaction, the parties can query poorly understood
elements, whereas the author of a written text must supply syntactic clues to
reduce the likelihood of misunderstandings impossible to correct by query.
Likewise, in displaying complex material, a single user interacting with a
display can build a representation of the dataspace in an informal and
unstructured way, as one might when using a blackboard, whereas a display
created for later viewing by other people must contain culturally appropriate
syntactic clues that aid viewers to interpret it as the designer intended.
Interactive: Informal, unstructured
Mediated or Coordinated: semi-formal, structured
Passive: formal, culturally appropriate, structured.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework for Network Visualisation
Discussion plan:
• Nature of a Framework, and Ancestor frameworks (VisTG
Reference Model, RM-Vis Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
The Framework Concept
Survey
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework Worksheet Concept – 1
The Framework process starts with a worksheet of questions that define what one is
trying to achieve. The answers to these questions should serve to generate queries to
a database of potentially relevant applications or software tools.
A first draft worksheet was tried out for some diverse use-cases.
 An analogue to the current anti-terrorist intelligence situation, in Elizabethan England
(1570-1600), seeking evidence of any possible assassination plot against Elizabeth
 The spread of avian flu on farms
 The social network analysis of a terrorist network
 Protection of a computer network
Not all the questions were easy to answer for all use-cases, and the worksheet will be reviewed
and revised.
The questionnaire worksheet is intended to provide answers that could be used to develop
queries into a database of presentation techniques and available applications or software tools.
The results of these queries should lead either to suggestions for the immediate user, or to the
identification of gaps in the armoury of tools for network visualisation.
The next few slides show the questions used in the first draft worksheet.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework Worksheet Concept – 1
The worksheet progresses in stages, starting with the overt problem definition,
followed by questions of the network properties, the dataspace, any dynamic issues,
context, measures, resources, and so on. It will be developed and the stages and
questions modified as a result of experience with use-cases. This is a first draft.
Stage 1. Defining the problem
What are you trying to understand? What questions are you trying to
answer?
Are you monitoring or influencing a changing situation?
Are you seeking a particular point of information?
Are you exploring the network structure for future reference?
Do you want to be notified when or where a particular condition occurs?
Does your problem concern the structure of the network or the traffic over
the network?
Does your problem involve local key points of the network or is it
distributed over appreciable subnets?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework Worksheet Concept – 2
Stage 2. Defining your network
What are the categories of nodes involved?
For each category of nodes you named, list the relationships or ties that may
exist between nodes in that category (not the traffic that passes therein)
Then, for each pair of categories list the relationships or ties that may exist
between pairs of nodes (one from each category)
Does traffic pass between nodes? If so, of what kind (continuous, regular,
predictably intermittent, unpredictably intermittent, etc.). If not, what is the
nature of the links?
If there is traffic, is the structure of the network defined by the traffic or
does it exist independently of whether there actually is traffic over any link?
For each category of node, does it transform its inputs into different kinds
of output. If so, how?
For each category of node, can the timing of input and output events be
related (i.e. are there fixed or variable delays, must two or more inputs
occur before an output happens, etc.)
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework Worksheet Concept – 3
Stage 3. Important Embedding fields (context) of the network
What context is important for understanding the network
Is the most important context a supporting network or a spatially extended
area, or something else?
Stage 4. Defining your measures
For each category you named, what about the nodes of that category will
you measure?
For each tie or relationship you named, what about the relationships will
you measure?
For any subnetwork of your overall network, what about that subnetwork
will you measure?
For your overall network, what about your overall network will you
measure?
Stage 5. Defining your resources
Where will you get your data? (Structured Text / Databases, Unstructured
Text/Documents, Sensor Readings, Other)
Are your data predefined for you; can you seek out data to fill gaps in your
knowledge; or is the data continually being presented to you in real time?
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework Worksheet Concept – 4
Stage 6. Domain Context
Task dynamics and interactivity (Real time, short term, long term, static)
Perceptual modes and activities (Control/Monitor, Search, Explore, Alert)
User Role
Stage 7. Network Aspects
Nodes (Single Mode, Multi-Modal)
Links (Simple, multiplex)
Metrics (Single metric, Multiple metrics)
Stage 8. General Data Characteristics
Temporal Variation (Static, Dynamic)
Data selection (User-selected, interactive, preset, algorithmically directed)
Data placement (Located vs. labelled, point vs. extended, interactive vs. passive)
Data values (Analogue vs. categorical, scalar vs. vector, linguistic vs. non-linguistic, crisp vs. fuzzy)
Data manipulation (Interactive vs. algorithmic)
Data Interrelations (User structured, algorithmically structured, externally defined)
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework and Survey
Answering the questions in the Framework Worksheet should
help the user understand the problem better.
Since both the Survey and the worksheet questions were
designed using the RM-Vis as a basis, the worksheet answers
should be compatible with the Survey dimensions of
description.
The worksheet answers help generate queries into the Survey
database. Initially this will have to be done manually, but it is
hoped that it will eventually be done by software, or at least
with software assistance.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework for Network Visualisation
Discussion plan:
• Nature of a Framework, and Ancestor frameworks (VisTG
Reference Model, RM-Vis Framework)
• Modes of perception and user task requirements
• Kinds of networks and of network properties
• Embedding fields and context (of networks and of displays)
• Dimensions of description for data and for displays
• Using the Framework and Survey
• Summary and future work
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Summary: Framework for Network Visualisation
•Many different kinds of network representation have been developed, but without a
coherent foundation that would allow good representations to be used for other
projects. A good Framework provides that foundation.
•A good representation supports the purposes of a user effectively.
•A Framework requires consideration of both the user or users and the range of
network properties that might be represented in support of the user’s purposes.
Therefore a Framework must consider the nature of real networks as well as the
properties of abstract mathematical graphs.
•Real networks are more complicated than are the abstract mathematical networks,
though the mathematics remains relevant to the real networks.
•Real networks are often fuzzy. Links and nodes may be of variable quality. Nodes
transform the kinds of traffic they receive and emit.
•Real networks are embedded in user-relevant context that affects their properties
and behaviour. The context may itself be a network.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework — The Way Ahead
1.
Complete the Framework by
•
•
•
Categorizing computable network attributes
Categorizing Network-related user tasks
Categorizing network-related display techniques
•
Develop mappings across categorizations:
o
task - attribute
o
attribute - display
Incorporate interaction (the theme of the follow-on RTG)
•
2.
Link the Framework with the Survey of Network Visualisation Software
3.
Describe the Framework process for end users
•
Propose support software to guide the user in the Framework process
4.
Test Framework use in different scenarios, and rework
5.
Publish for general use.
IST-059/RTG-025 does not have the resources to complete all the above!
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
NATO RTO IST-059/RTG-025
Network Visualisation
A Work in Progress
http://www.vistg.net
M. Martin Taylor (Secretary, IST-059/RTG-025)
Martin Taylor Consulting
[email protected]
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
A Brief Background to NATO RTO IST-059/RTG-025
1993-4 NATO Defence Research Group (DRG) Exploratory group on
Visualising Non-Visual Data (primarily free text documents), led to
1996 AC/243(Panel 8)/RSG-30Visualizing Massive Military Datasets
In 1997 NATO elements DRG and AGARD were combined to form the Research
and Technology Organization (RTO) and Panel 8/RSG-30 became
1997 IST-013/RTG-002 Visualizing Massive Military Datasets which produced
2001 The “HAT Report”: RTO-TR-030 Visualisation of Massive Military
Datasets: Human Factors, Applications, and Technologies. A major report that
included the VisTG Reference Model, which provided the background for
2001 IST-021/RTG-007 Visualizing Massive Military Datasets, which
recognized the importance of representing networks, and led on to the present
2005 IST-059/RTG-025 Visualising Network Data, which has been developing a
Framework for Network Visualisation.
Providing continuity, these groups have all been
colloquially called “VisTG”
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Workshops
The following workshops have been either organized by the N/X or sponsored by VisTG.
June 1996, Ottawa, Canada (N/X). Visualisation of non-visual data
May 1997, Malvern, UK (N/X). Visualization in Massive [Military] Datasets
June 1998, Toronto, Canada (N/X). Visualization in Massive Military Datasets
June 1999, Malvern, UK (N/X). (No specified Theme)
June2000, Quebec, Canada (IST-020/RWS002) Visualisation of Massive Military Datasets
Oct 2001, Aalborg, Denmark (N/X), (No specified Theme)
Sept 2002, Halden, Norway (IST-036/RWS-005) Visualisation of Massive Military Datasets:
Users talk to Developers
March 2003, State College, PA, USA (NX) Visualisation for Intelligence and Counter-Terror
June 2004, Toronto, Canada (IST-043/RWS-006) Visualisation and the Common Operational
Picture
Oct 2005, Wachtberg-Werthoven, Germany (NX) Social Network Analysis and Visualisation for
Public Safety
Oct 2006 Copenhagen, Denmark (IST-063/RWS-010) Visualising Network Information
Workshops with IST numbers are official NATO Workshops,
Their Proceedings are available from http://www.rta.nato.int
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Perceptual modes
One of the dimensions of the RM-Vis reference model is “Domain
Context”, which specifies an application area. Each domain context
has its own specific possibilities for the four perceptual modes, so the
VisTG Framework does no more than to suggest to the user that the
requirements be identified in each of the four modes.
For example, in an anti-terrorist application,
Exploring might use network analysis to identify groups of
people worth
Monitoring or influencing (i.e Controlling), while
Searching might seek out those in interesting groups who have
specific areas of expertise, and
Alerting might set up automated procedures to look for certain
types of traffic in particular areas of the identified network.
Each of these implies different requirements for display.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Follow-on RTG: Terms of Reference (extract)
Research topics include:
• Visualisation for interactive simulation for complex network discovery and
network behaviour prediction
• representation of abstract concepts
• simulation for prediction and discovery
• understanding network "black box" behaviour
• effects of external forces on network behaviour
• Applications to Situation Awareness and Decision Support
• Applications to social networks including terrorist networks, disease
propagation, time dependent and dynamic networks
• Scalability issues
• Further development of the Visualisation Framework (to be) delivered by
IST-059/RTG-025, particularly in respect of interaction.
This new RTG has been approved. It may start in Jan 2009 while IST-059/RTG025 in 2008 continues to develop the Survey and Framework in the indicated
direction.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
More about VisTG generally
Member nations have included: Canada, Denmark, Germany, Norway, Portugal,
Slovakia, UK, USA; currently Portugal and Slovakia do not participate. Meeting
are held twice each year, rotating among the member nations.
NATO Workshops:
VisTG has sponsored a sequence of four-day NATO Workshops. These are based
around the work of small break-out groups, each working intensively on one of a
menu of topics proposed by VisTG. Formal presentations are used mainly as
introductions to the topics on the menu for the working groups.
The Network of Experts (N/X):
The Network of Experts is an invited group of people interested in the topics
addressed by VisTG. They need not belong to NATO nations. The Network of
Experts organizes N/X workshops on both sides of the Atlantic, usually for two days
in conjunction with a meeting of VisTG. Either a NATO workshop or a N/X
workshop has been held each year since 1996. Most N/X members are members
because they have attended one or more of these workshops. There is a mailing list
(not very active) and a Web site (http://www.visn-x.net).
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
IST-059/RTG-025 Programme
IST-059/RTG-025 is scheduled to terminate Dec 31, 2007, and a new RTG has been
accepted in principle, with the topic “Interactive Visualisation of Network Behaviour”.
(However, if the bureaucratic processes don’t permit the new RTG to start until 2009, IST059 has requested a year’s extension to permit continuity of the work).
Two meetings will be held in 2007 (June in Malvern, UK, and November in Redondo
beach, CA, USA). An N/X Workshop Visualization for Simulation & Prediction will be
organized in conjunction with the November USA meeting. Planning is also under way
for a NATO workshop in 2008, though this may slip to 2009 if the new RTG is delayed.
IST-059/RTG-025 took as its major projects (1) a survey of existing support for network
visualisation, and (2) the development of a Framework for network visualisation.
The survey currently lists 139 items, ranging from general software such as Mathematica
to routines that can be compiled into programmes, to support graph drawing. It can be
seen and edited at http://www.vis-discuss.net/vizsurvey (password required).
The Framework is a development from the VisTG Reference Model introduced by IST013/RTG-002 in the HAT report, together with the RM-Vis Reference Model produced by
TTCP C3I AG3. The Framework introduces the concept of “Embedding Spaces” both of
networks and of displays, and has been conceptually integrated with the survey as a
workflow that should provide the basis for a tool useful both to users and to developers.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework: Categorizing Display Techniques
One approach to categorizing: Survey and collate.
In parallel with the Framework Working Group, IST-059/RTG-025
has another Working Group developing an on-line Survey of network
visualisation software. The survey is expected to be useful in its own
right, but analysis of the properties of the surveyed items should also
assist in developing the Framework categories. The Framework
categories would then be useable for accessing the Survey database.
Intuitive Categories
The Survey uses intuitively derived categories for describing the
software. Some of them are irrelevant to the Framework, such as
cost, open-source versus proprietary, hardware platform, coding
language and extensibility, etc. Others are highly relevant, some
being derived directly from the RM-Vis reference model.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Survey Partial Screenshot
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
RM-Vis Reference Model developed by TTCP C31 AG-3
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Framework-Survey Integration — Workflow
User task
Algorithm Selection
Network Properties
Data Type Selection
Queries
Survey Database
Display Type Selection
Display Design
Platform
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Using the Framework
Framework
Survey DB
Analyst Notebook
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Network Properties


Data Type
Display Requirements


Display Design
Matrix of Pointers
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation
Embedding fields of real networks
The concept of an “embedding field” was triggered by a pair of hypothesized
assertions within IST-059/RTG-025:
1.
A physical network always has the possibility that a conceptual network
lies on top of it. The conceptual network may map homologously onto the
physical network if the relationships between nodes are defined as such,
but in most cases, the conceptual network involves only subsets of the
physical network.
2.
A conceptual network may exist without any underlying physical network.
Examining these assertions led to the concept of an “embedding field” for a
network. The concept applies whether or not the network has a physical
substrate.
Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation