The VisTG Framework for Network Visualisation Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation

The VisTG Framework forNetwork Visualisation

Based on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network Visualisation

M. Martin Taylor (Secretary, IST-059/RTG-025)Martin Taylor Consulting

[email protected]

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 on report to IST-063/RWS-010 by the IST-059/RTG-025 Working Group on Framework for Network 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.

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


Why develop a Framework for Network Visualisation?


•IST-059 considered that the very concept of a real world network is ill-defined. 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.

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.

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



C2 Network Visualisation Approaches (From Vernik-Bouchard Presentationat the IST-063/RWS-010 Workshop,Copenhagen October 2006)

A Framework for Network VisualisationThe 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.


The Framework Concept




Survey

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.


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


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!

The VisTG Reference Model


RM-Vis Reference Model developed by TTCP C31 AG-3


Framework for Network Visualisation

Discussion plan:

• Nature of a Framework, and Ancestor frameworks (VisTG Reference Model, RM-Vis Framework)








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.


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.

Framework: Perceptual mode implications for display

The four modes often have implications for display: e.g. in an anti-terrorist scenario



Discussion plan:









• 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?

Framework roots: Network properties


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 node-like, and indefinitely linked to other nodes. The membership of an element in class “node” or “link” may depend on the user’s purpose.


Fuzzy Nodes and Links

A BRoad between two towns

A and B is a link

A 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.

X

The cluster becomes a new town

Original situation1

A BIs the road between A and B a link? Yes, Pretty much. Is the

farm a node? Hardly.

Farm

A Farmhouse is built near the road2

A 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!

Farm

Gas Hotel

More facilities are built to service travellers3 4


Fuzzy link membership should not be confused with link weight. Here’s a simple example

Varieties of Link “Strength” – 1: BasicIn 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 SimilarityHow 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?

Varieties of Link “Strength” – 2: ComplexityA 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”?

Transformational properties of nodes and linksIn 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?


Mathematical PropertiesMost 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?


Discussion plan:









Real NetworksAre 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.


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.


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.

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.

Embedding fields of real networks – 2Networks are often displayed along with some aspect of their embedding field to supply context.

But not always:

Two representations of part of the Internet.


Embedding fields of real networks – 3The 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.


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.



Discussion plan:









Framework: Categorizing Data TypesSix Descriptive Dimensions

from the Final Report of IST-013/RTG-002 (The HAT Report)

Values

Analoguescalar

vector

Categoric (crisp)

symbolic

linguistic

Non-linguistic

non-symbolic

linguistic

Non-linguistic

Categoric (fuzzy)

symbolic (non-linguistic)

non-symbolic (non-linguistic)

RelationsUser-structured

Source-structured

AcquisitionStreamed

Sporadic

Regular

Static

SourcesSingle

Multiple

Choice

User-selected interactive

Externally imposed

IdentificationLocated

Labelled


Framework: Categorizing Display Techniques

Display TimingStatic picture

Dynamic variation

Data SelectionUser-selected

Algorithmically selected

Data PlacementLocated

Labelled

Data Values

Analoguescalar

vector

Categoriclinguistic

symbolic

Four Descriptive Dimensions from the Final Report of IST-013/RTG-002 (The HAT Report)


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.


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 end-users; 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.

Framework: Interaction modesThe display may be for a single user or for multiple users


Framework: Interaction modes – 2Interaction 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

Interactive Coordinated Mediated Passive

Single end-user All Modes N/AExplore,Search

Explore

Multiple Usersviewingsimultaneously

N/AMonitor,

Explore, Search,Alert

Explore Explore

Multiple usersviewing separately

N/AMonitor,

Explore, Search,Alert

N/A Explore

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.

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.


Discussion plan:











Survey

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.



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?

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 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.)



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?



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)

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.



Discussion plan:









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.


Framework — The Way Ahead1. Complete the Framework by

• Categorizing computable network attributes• Categorizing Network-related user tasks• Categorizing network-related display techniques

• Develop mappings across categorizations:o task - attributeo 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-025Network Visualisation

A Work in Progress

http://www.vistg.net


M. Martin Taylor (Secretary, IST-059/RTG-025)Martin Taylor Consulting

[email protected]


A Brief Background to NATO RTO IST-059/RTG-0251993-4 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”


WorkshopsThe 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

Framework: Perceptual modesOne 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/RTG-025 in 2008 continues to develop the Survey and Framework in the indicated direction.


More about VisTG generallyMember 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).


IST-059/RTG-025 ProgrammeIST-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, IST-059 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 IST-013/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.

http://www.vis-discuss.net/vizsurvey

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.



Survey Partial Screenshot

RM-Vis Reference Model developed by TTCP C31 AG-3


Framework-Survey Integration — Workflow

User task Algorithm Selection

Network Properties

Data Type Selection

Display Type Selection

Display Design Platform

Survey DatabaseQueries


Using the Framework

Network Properties

Data Type

Display Requirements

Display Design

Survey DB

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Matrix of Pointers

Framework

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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.
