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Fitts's Law

by Mehmet Goktrk. How to cite in your report.
 
 

First of all it is not Fitts Law. The name of the famous researcher is Paul Fitts, so one should be careful on spelling. Fitts's Law is basically an empirical model explaining speed-accuracy tradeoff characteristics of human muscle movement with some analogy to Shannons channel capacity theorem. Today, with the advent of graphical user interfaces and different styles of interaction, Fitts Law seems to have more importance than ever before.

The early experiments on pointing movements targeted the tasks that might be related to the worker efficiency problem, such as production line and assembly tasks. They were not targeted to HCI field because there was no GUI. Paul Fitts extended Woodworth's research which focused on telegraph operator performance substantially with his famous reciprocal tapping task to define the well-referenced Fitts Law (Fitts 1954). In the Fitts Law description of pointing, the parameters of interest are:

a. The time to move to the target
b. The movement distance from the starting position to the target center
c. Target width

Fitts started his work making an analogy of the human motor system to the well-known Shannon's channel capacity theorem. He started with the following theorem:

sdaf(1)

in the above equation, C represents the effective information capacity of the communication channel, B represents the bandwidth of the channel, S and N represent signal and allowable noise power levels respectively. Fitts claimed that the distance (A) can be thought as signal power, the width of the target (W) can be thought as the allowable noise. As powerful transmitters carry more information, it becomes harder to receive when the allowable noise level increases. Similarly, it takes longer to hit targets which are further away and smaller. With this analogy, he derived the following equation, which is now known as Fitts Law:

asdf(2)

here, MT represents the movement time to hit the target, a and b are empirically determined constants. A represents the amplitude, which is the distance of the center of the target from the starting location and W is the target width which is shown in Figure 2.

asdf
Figure 2. The basic pointing task variables A and W.

The empirical constants a and b are found using a regression analysis on the movement time data. A typical Fitts regression line appears as follows:

asdf
Figure 3. Fitts regression line.

In almost all of the research following the Fitts' original experiment, the empirically determined constant a, is usually considered to include a constant time, such as depressing a mouse button depending on the experiment. (Note that the definition of movement time has no strong specification for the boundary conditions). Fitts defined the term Index of Difficulty (ID, shown in Figure 3), as a measure of the task difficulty as follows:

asdf(3)

Mackenzie (MacKenzie 1992), suggested a more stable model for the Fitts Law, which works better -also more like the Shannons original formula- for the small values of ID as follows:

asdf(2a)
asdf(3a)

Index of difficulty is measured in terms of "bits", which comes from the analogy with Shannon's information theorem. In addition to the index of difficulty, Fitts also defined a measure for the performance, named Index of Performance (IP) which is as follows:

asdf(4)

Index of performance is measured in bits per second (bits/sec), similar to the performance indices of the electronic communication devices (e.g. modems). Fitts claimed that under ideal circumstances the term a in Equation 2 would be zero, therefore the index of performance (IP) can be simply taken as ID/MT from Equation 2. However, later by other researchers, the constant a is proven to be a significant factor emphasizing the need for a more detailed analysis. The constant term a is also shown to be highly affected by the learning curve (Card 1991) of the input device and the task.

Welford, suggested a better model by separating A and W into two terms. He indicated that the effect of the target width and the target distance is not proportional and his model yields a better correlation coefficient (Welford 1968). Later researchers suggested the same. However, there is no simple index of performance associated with Welfords model.

sadf (5)

Fitts had subjects move a stylus alternately back and forth between two separate target regions, tapping one or the other target at the end of each movement. These types of tasks are called continuous tasks where the subject is not expected to stop after finishing one movement but instructed to repeat the same task symmetrically as quickly as possible. In continuous tasks, the total time is divided by the number of movements to determine the average movement time for a particular target size and distance. The other type, discrete tasks, on the other hand, are tasks where the subject is instructed to stop after one movement and the time is measured between the start and the end-points. Subjects were instructed to make their aimed movements as rapidly as possible but land within the boundaries of the targets on at least 95% of the taps. Fitts varied the size and distance of the targets in his experiments. For his reciprocal tapping task, he obtained an ID value of about 10bits/sec.

Paul Fitts conducted three different experiments in his study; the famous reciprocal stylus tapping task with two different stylus weights (1oz and 1lb), the disc transfer task and the pin transfer tasks. The latter two tasks were more demanding in terms of the endpoint difficulties, and resulted higher constant values for the regression coefficient for similar values of indices of performances. This in fact was the first indication of the variability of the endpoint selection time in Fitts' experiment. However, Fitts did not mention this effect in detail in his original publication (Fitts 1954). Fitts original data was later reviewed by many researchers (Fitts 1964), (Sheridan 1979), (Welford 1986), (MacKenzie 1992) and different opinions criticized the validity of the Fitts model.

Fitts later repeated the original study by himself (Fitts 1964) in discrete form and concluded that the original formula also holds for the discrete tapping tasks. Other researchers repeated similar experiments and found that Fitts Law holds for discrete tasks as well.

Fitts' experiment and the Fitts Law equation highlight the points that are important in pointing tasks such as pointing speed, target distance, target size and accuracy. Fitts Law gives us a way to compare tasks, limbs and devices both in manual as well as in computer pointing. Therefore one can conclude that devices with higher indices of performance would be faster and presumably better.

On the other hand, we also have to state that, Fitts Law does not provide any prediction of the performance of a limb or device. It does not provide information without conducting an experiment. It does not provide an absolute measure for a limb using particular device, rather, it is a comparative tool for studying different devices, tasks, interaction techniques or limbs. Attempts to define such a universal standard exist but are still being studied (MacKenzie 1999).

With the advent of new smaller technological devices, small screens, and highly loaded user interfaces, Fitts Law again becomes an important tool to measure what is better what is not, in terms of interface design. For example, increased screen density (DPI) due to higher resolution graphics cards usually result in smaller menu buttons on identical monitors. Yet, advantage of having more pixels on same screen bounces back to user as longer click times and higher error rates. The problem becomes more severe as user clicks via low performer input devices such as trackpads. Using bigger LCD monitors does not improve the condition: Although the target size returns to normal, users are expected to travel longer distances on screen (Not only with input device but also with their eyes).

The key factor is, to reduce required travel distance from one location to another as user navigates through the interface and maintaining a proper size affordance for clicking. Repositioning the cursor has been suggested for this reason, however, it must be done carefully without causing user to lose locus of control. Reorganization of navigational elements, menus, buttons so that frequently used elements are placed closer to neutral cursor position is helpful to increase performance. Elimination of very narrow hierarchical menu height or elimination of hierarchical menus altogether where possible can also improve interface performance due to Fittss Law characteristics of such. Dynamic approaches such as zooming icons (Mac OS X desktop) and gravity wells are known as effective performance improvement methods but must be used with great caution without causing other side effects.

There are numerous computer applications that focus on performance comparison of input devices and human speed-accuracy tradeoff. One online example of such can be found at http://www.tele-actor.net/fitts/ where performance of participants are plotted after the experiment and compared against visitors hall of fame list. Another Fitts Law application which is organized as a game is Fittsbits, and can be reached at: http://www.rodo.nl/fittsbits/index.php?page=home.

How to learn more

For futher information, a good starting point could be the special issue of the International Journal of Human Computer Studies, focused on Fitts Law. (Volume 61 , Issue 6 , 2004, ISSN:1071-5819 , Academic Press).

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        Legal Code (full licence text): http://creativecommons.org/licenses/by-nd/1.0/
  13. CC-Att-ND:
        Creative Commons Attribution-NoDerivs 3.0 Unported
        Legal Code (full licence text): http://creativecommons.org/licenses/by-nd/3.0/
  14. CC-Att-SA-1:
        Creative Commons Attribution-ShareAlike 1.0 Unported
        Legal Code (full licence text): http://creativecommons.org/licenses/by-sa/1.0/
  15. CC-Att-NC-SA-3:
        Attribution-NonCommercial-ShareAlike 3.0 Unported
        Legal Code (full licence text): http://creativecommons.org/licenses/by-nc-sa/3.0/
  16. CC-Att-SA-3:
        Creative Commons Attribution-ShareAlike 3.0
        Legal Code (full licence text): http://creativecommons.org/licenses/by-sa/3.0/
  17. CC-Att-SA-2:
        Creative Commons Attribution-ShareAlike 2.0 Unported
        Legal Code (full licence text): http://creativecommons.org/licenses/by-sa/2.0/
  18. CC-Att-SA:
        Creative Commons Attribution-ShareAlike 3.0 Unported
        Legal Code (full licence text): http://creativecommons.org/licenses/by-sa/3.0/
  19. Unknown:
        Copyright status unknown
  20. Trademarks and logos:
        All trademarks, logos, service marks, collective marks, design rights, personality rights or similar rights that are mentioned, used or cited by The Interaction Design Foundation and its authors are the property of their respective owners. The use of any trademark in our materials does not vest in the author or The Interaction Design Foundation any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of The Interaction Design Foundation and its authors by such owners. As such The Interaction Design Foundation can not grant any rights to use any otherwise protected materials. Your use of any such or similar incorporeal property is at your own risk. Words which we have reason to believe constitute trademarks may or may not have been labelled as such. However, neither the presence nor absence of such labels should be regarded as affecting the legal status of any trademarks.

While most material produced by The Interaction Design Foundation is free to use under its respective license as outlined above, some materials may be subject to additional legal restrictions when they are used in particular circumstances or in particular ways. These limitations may arise from laws related to trademarks, patents, personality rights, political censorship, or any of many other legal causes which are entirely independent from the copyright status of the work. For example, if you use a public domain image (i.e. uncopyrighted) of an apple to sell computers, you will violate the trademark rights of Apple Computer, Inc.

In addition, content linked from a page/chapter/book (in the online versions) is not covered by one of our licenses unless specifically noted. For example, pages may link to videos or slide decks that are not covered. The design of Interaction-Design.org (graphics, html, client-side scripts, etc.) is copyright of Mads Soegaard.

iv. The Site Terms and Conditions

These Site Terms and Conditions ("Terms") is a legally binding agreement made by and between The Interaction Design Foundation and you, personally and, if applicable, on behalf of the entity for whom you are using this web site or any of its services (collectively, "you"). These Terms govern your use of The Interaction Design Foundation's web site, www.interaction-design.org, and The Interaction Design Foundation's services so please read the following carefully.

By accessing or using any part of the web site, you agree that you have read, understand, and agree to be bound by this Terms. if you do not agree to be so bound, do not access or use the web site.

Internet technology and the applicable laws, rules, and regulations change frequently. Accordingly, The Interaction Design Foundation reserves the right to make changes to these Terms at any time. Your continued use of the web site constitutes assent to any new or modified provision of this Terms that may be posted on the web site.

These Terms addresses your legal rights and obligations and includes important disclaimers and choice of law and forum provisions.

1. Choice of Law and Forum Provisions (Governing Law)

Interaction-Design.org is run by The Interaction Design Foundation, a privately held corporation residing in Aarhus, Denmark. You agree that these Terms and your use of Interaction-Design.org and the materials produced by The Interaction Design Foundation are governed by the laws of Denmark. You hereby consent to the exclusive jurisdiction and venue of the courts, tribunals, agencies and other dispute resolution organizations in Denmark in all disputes

  1. arising out of, relating to, or concerning Interaction-Design.org, The Interaction Design Foundation, and/or these Terms
  2. in which Interaction-Design.org, The Interaction Design Foundation, and/or these Terms is an issue or a material fact
  3. or in which Interaction-Design.org, The Interaction Design Foundation, and/or these Terms is referenced in a paper filed in a court, tribunal, agency or other dispute resolution organization.

The Interaction Design Foundation has endeavoured to comply with all legal requirements known to it in creating and maintaining Interaction-Design.org and The Interaction Design Foundation, but makes no representation that materials on Interaction-Design.org or produced by The Interaction Design Foundation are appropriate or available for use in any particular jurisdiction. You are responsible for compliance with applicable laws. Any use in contravention of this provision or any provision of these Terms is at your own risk and, if any part of these Terms is invalid or unenforceable under applicable law, the invalid or unenforceable provision will be deemed superseded by a valid, enforceable provision that most closely matches the intent of the original provision and the remainder of these Terms shall govern such use.

2. Liability

Your use of and browsing Interaction-Design.org is at your own risk. The Interaction Design Foundation does not warrant that the software used for Interaction-Design.org, and the information, material, and content on it, or any other services and materials provided by means of Interaction-Design.org or by The Interaction Design Foundation are error-free, or that their use will be uninterrupted. The Interaction Design Foundation expressly disclaims all warranties related to the above-mentioned subject matter, including, without limitation, those of accuracy, condition, merchantability and fitness for particular purpose. Notwithstanding anything to the contrary on Interaction-Design.org, in no event shall The Interaction Design Foundation be liable for any loss of profits, revenues, indirect, special, incidental, consequential, or other similar damages arising out of or in connection with Interaction-Design.org or out of the use of any of the services proposed by means of Interaction-Design.org.

3. Updates

Internet technology, publishing technology, and the applicable laws, rules, and regulations change frequently. Accordingly, The Interaction Design Foundation reserves the unilateral right to update, modify, change and alter its Site Terms and Conditions as well as Copyright Terms at any time. All such updates, modifications, changes and alterations are binding on all users and browsers of Interaction-Design.org, readers of electronic and non-eletronic versions of the publications produced by The Interaction Design Foundation. Such updates will be posted on Interaction-Design.org.

4. Legal Disclaimer

The Interaction Design Foundation and its authors make no representations as to accuracy, completeness, currentness, suitability, or validity of any information, material, or content on Interaction-Design.org.

THE MATERIAL AND CONTENT POSTED ON INTERACTION-DESIGN.ORG AND ANY CONTENT PROUDCED BY - OR PUBLISHED THROUGH THE INTERACTION DESIGN FOUNDATION ARE PROVIDED "AS IS" WITHOUT ANY EXPRESS WARRANTY OR IMPLIED WARRANTY OF ANY KIND INCLUDING WARRANTIES OF MERCHANTABILITY, NON-INFRINGEMENT OF INTELLECTUAL PROPERTY, OR FITNESS FOR ANY PARTICULAR PURPOSE. IN NO EVENT SHALL THE INTERACTION DESIGN FOUNDATION BE LIABLE FOR ANY DAMAGES WHATSOEVER (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF PROFITS, BUSINESS INTERRUPTION, LOSS OF INFORMATION) ARISING OUT OF THE USE OF OR INABILITY TO USE THE MATERIALS, EVEN IF THE INTERACTION DESIGN FOUNDATION HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Because some jurisdictions prohibit the exclusion or limitation of liability for consequential and or incidental damages, the above limitation may not apply to you. Furthermore, The Interaction Design Foundation does not warrant the accuracy or completeness of information of links or other items contained within these materials that have been provided by third parties.

5. Provision regarding change in attribution of copyrighted materials

Please contact us at mads@interaction-design.org if you, or your organization, wish to correct or change attribution or presentation of any image/material used on Interaction-Design.org, which you, or your organization, are the rightful copyright holder of. We will request that you submit proof of your ownership of the copyright on this material but will act immediately on any reasonable request.

6. Notice and prodecure for claims of copyright infringement

Every effort has been made by the individual contributing authors as well as The Interaction Design Foundation to discover and contact copyright holders of artwork/illustrations/content used on Interaction-Design.org. To the extent that a copyright holder could not be found or an inadvertent permissions or copyright error was made, The Interaction Design Foundation stands ready to remove content upon notice and request by a copyright holder. In the case that you believe that any content or other material provided through Interaction-Design.org infringes your copyright, you should notify The Interaction Design Foundation of your infringement claim in accordance with the procedure set forth below.

We will process each notice of alleged infringement which The Interaction Design Foundation receives and take appropriate action in accordance with applicable intellectual property laws. A notification of claimed copyright infringement should be emailed to mads@interaction-design.org (subject: "Takedown Request"). You may also contact us by mail at:

The Interaction Design Foundation
Chr. Molbechs Vej 4
DK-8000 Aarhus C.
Denmark

To be effective, the notification must be in writing and contain the following information:

  1. an electronic or physical signature of the copyright owner or the person authorized to act on behalf of the owner of the copyright interest
  2. a description of the copyrighted work that you claim has been infringed
  3. a description of where the material that you claim is infringing is located on Interaction-Design.org that is reasonably sufficient to enable us to identify and locate the material;
  4. how The Interaction Design Foundation can contact you, such as your address, telephone number, and email address
  5. a written statement by you that you have a good faith belief that the disputed use is not authorized by the copyright owner, its agent, or the law
  6. if you represent a publisher, a written statement by you that you have a good faith belief that the material has not been placed in the public domain, or licenced under another licence, before you acquired the copyright as this would possibly invalidate your copyright
  7. and a statement by you, made under penalty of perjury, that the above information in your notice is accurate and that you are the copyright owner or authorized to act on the copyright owner's behalf.

7. Trademarks and other rights

All trademarks, logos, service marks, collective marks, design rights, personality rights or similar rights that are mentioned, used or cited by The Interaction Design Foundation and its authors are the property of their respective owners. The use of any trademark in our materials does not vest in the author or The Interaction Design Foundation any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of The Interaction Design Foundation and its authors by such owners. As such The Interaction Design Foundation can not grant any rights to use any otherwise protected materials. Your use of any such or similar incorporeal property is at your own risk. Words which we have reason to believe constitute trademarks may or may not have been labelled as such. However, neither the presence nor absence of such labels should be regarded as affecting the legal status of any trademarks.

8. Screenshots

Screenshots of copyrighted computer software, for which the copyright is held by the author(s) or the company that created the software, is believed to fall under the fair use doctrine in the US (and similar laws in other countries). It is believed that reproduction for purposes such as criticism, comment, news reporting, teaching, or research is not copyright infringement. If you reuse screenshots, as well as any other information provided by The Interaction Design Foundation, you do so at your own risk and under the copyright laws of your country.

9. Copyright of Abstracts

Abstracts in the Wiki Bibliography (/references/) are submitted by their authors who use the wiki to make their research as accessible as possible. When a page on Interaction-Design.org cites/references/lists a work from the bibliography, its abstract is included. However, abstracts have varying copyrights depending which publisher the work is published through. You should assume that an abstract is copyright, all rights reserved, of its publisher and/or author and therefore always use/cite abstracts according to Fair Use. You may visit the publisher's website to learn about the specific copyright terms (e.g. ACM, IEEE, or Springer) or contact the author directly. Bottom line: Cite/use abstracts according to the principles of fair use as it may otherwise be construed as a copyright infringement and subject to legal action.

10. User Submissions / User Content

You understand and acknowledge that additions to the Wiki Bibliography (including article abstracts), additions the Conference Calendar (including conference descriptions), user-contributed notes on each page (including text, photographs, graphics), or other materials posted by users on Interaction-Design.org ("Content") are the sole responsibility of the person from whom such Content originated. This means that you, and not The Interaction Design Foundation, are entirely responsible for all Content that you upload, post or otherwise make available to other users of Interaction-Design.org.

When submitting content to Interaction-Design.org, you agree to not:

  1. impersonate any person or entity or falsely state or otherwise misrepresent your affiliation with a person or entity;
  2. upload, post or otherwise make available any Content that you do not have a right to make available under any law or under contractual or fiduciary relationships (such as inside information, proprietary and confidential information learned or disclosed as part of employment relationships or under nondisclosure agreements);
  3. upload, post or otherwise make available any Content that infringes any patent, trademark, trade secret, copyright or other proprietary rights ("Rights") of any party;
  4. upload, post or otherwise make available any Content that is unlawful, harmful, threatening, abusive, harassing, tortious, defamatory, vulgar, obscene, libelous, invasive of another's privacy, hateful, or racially, ethnically or otherwise objectionable;

You acknowledge that The Interaction Design Foundation shall have the right to remove any Content that violates these Site Terms and Conditions or is otherwise objectionable.

11. Third Party Websites

If we provide links or pointers to other websites, no inference or assumption should be made that The Interaction Design Foundation operates, controls, or is otherwise connected with these websites. When you click on a link within Interaction-Design.org, we will not warn you that you have left a Site and are subject to the terms and conditions (including privacy policies) of the destination website. In some cases it may be less obvious than others that you have left a Site and reached another website. Please be careful to read the terms of use and privacy policy of any website before you provide any confidential information or engage in any transactions. You should not rely on these Terms for another website. The Interaction Design Foundation is not responsible for the content or practices of any other website. By using Interaction-Design.org, you acknowledge and agree that The Interaction Design Foundation is not responsible or liable to you for any content or other materials hosted and served from any third party website.

12. Email communication: Confidential and proprietary information notice

Email messages sent from members of The Interaction Design Foundation, including emails generated from the use of the interaction-design.org website, are proprietary to The Interaction Design Foundation, and are intended solely for the use of the individual to whom they are addressed. Such messages may contain privileged or confidential information and should not be circulated or used for any purpose other than for what they are intended. If you receive a message from a member of The Interaction Design Foundation in error, please notify the sender immediately. If you are not the intended recipient, you are hereby notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of the message. The Interaction Design Foundation accepts no responsibility for loss or damage arising from the use of the information transmitted by email message including damage from virus.

13. Usage conditions

Please make sure that you understand that the information provided by The Interaction Design Foundation is being provided freely, and that no kind of agreement or contract is created between you and the owners, partners, users, or authors of this site, the owners of the servers upon which it is housed, the individual contributors of the The Interaction Design Foundation, any project administrators, sysops or anyone else who is in any way connected with this project. If you choose to use or copy anything from from this site it does not create or imply any contractual or extracontractual liability on the part of The Interaction Design Foundation or any of its members, partners, sponsors, contributors or other users. Your use of any such or similar incorporeal property is at your own risk.

14. Termination

The Interaction Design Foundation will have the right to terminate your access to the Web Site if it reasonably believes you have breached any of the terms and conditions of these Terms. Following termination, you will not be permitted to use the Web Site. If your access to the Web Site is terminated, The Interaction Design Foundation reserves the right to exercise whatever means it deems necessary to prevent unauthorized access to the Web Site, including, but not limited to, technological barriers, IP mapping, and direct contact with your Internet Service Provider. These Terms will survive indefinitely unless and until The Interaction Design Foundation chooses to terminate them, regardless of whether any account you open is terminated by you or The Interaction Design Foundation or if you have the right to access or use the Web Site.

15. Force Majeure, website downtime, and service outages

The Interaction Design Foundation will not be liable for failing to perform under these Terms because of any event beyond its reasonable control, including, without limitation, a labor disturbance, an Internet outage or interruption of service, a communications outage, failure by a service provider to The Interaction Design Foundation to perform, fire, terrorism, natural disaster, or war.

16. Limitation of Actions

You acknowledge and agree that, regardless of any statute or law to the contrary, any claim or cause of action you may have arising out of, relating to, or connected with your use of the Web Site, must be filed within one calendar year after such claim or cause of action arises, or forever be barred.

17. Payments

Online payment is accepted by Paypal. The Interaction Design Foundation does not process credit card payments directly or ever see, retain, or use your credit card information.

18. Taxes and VAT

In the name of Simplicity for our members/clients and the online User Experience, our prices always include VAT when applicable. The Interaction Design Foundation is based in Denmark so we pay 25% VAT of payments - depending on which originating country the member or customer is from.

19. Ownership of Interaction-Design.org, The Interaction Design Foundation, and its services

Interaction-Design.org is owned and operated by The Interaction Design Foundation, an LLC incorporated under the laws of Denmark, with office in Aarhus, Denmark.

Address:
The Interaction Design Foundation
Chr. Molbechs Vej 4
DK-8000 Aarhus C.
Denmark

20. Changes to the Web Site

The Interaction Design Foundation may, in its sole discretion, change, modify, suspend, make improvements to, or discontinue any aspect of the Web Site, temporarily or permanently, at any time without notice to you, and The Interaction Design Foundation will not be liable for doing so.

21. Additional Terms

These Terms contain the entire understanding of you and The Interaction Design Foundation regarding the use of the Web Site and the services of The Interaction Design Foundation, and supersedes all prior and contemporaneous agreements and understandings between you and The Interaction Design Foundation relating thereto. These Terms will be binding upon each party hereto and its successors and permitted assigns. These Terms and all of your rights and obligations under them may not be assignable or transferable by you without the prior written consent of The Interaction Design Foundation. No failure or delay by a party in exercising any right, power, or privilege under these Terms will operate as a waiver thereof, nor will any single or partial exercise of any right, power or privilege preclude any other or further exercise thereof or the exercise of any other right, power, or privilege under these Terms. You and The Interaction Design Foundation are independent contractors, and no agency, partnership, joint venture, employee-employer relationship is intended or created by these Terms. The invalidity or unenforceability of any provision of these Terms will not affect the validity or enforceability of any other provision of these Terms, all of which will remain in full force and effect.

22. Legal Disputes

Any dispute arising from the use of Interaction-Design.org or the interpretation of the terms is governed by the laws of Denmark, and shall be settled by the courts of Denmark. All communications regarding legal matters must be made in writing to

The Interaction Design Foundation
Chr. Molbechs Vej 4
DK-8000 Aarhus C.
Denmark

iv. Site Privacy Policy

1. Summary

The Interaction Design Foundation collects no more data about you than most other websites.

Any membership information you provide to us will be used by us in order to maintain a register of members and supply you with any goods and services you have requested from our web site.

Edits, comments, commentaries and other contributions are published, and except in very limited circumstances, will be a permanent part of this site. If you decide contribute, you must keep this in mind. Your contributions will be subject to the Site Terms and Conditions and our Site IP/Copyright policy.

Under "The Act on Processing of Personal Data", incorporated under Danish law, you may request a copy of the information we hold on you (for which we may charge a fee to offset our administration costs) by writing to us .

This privacy policy will be reviewed, and may be revised, from time to time. You may wish to revisit it regularly.

2. No selling of information

We do not share or sell email addresses, obtained via communication with visitors, with anyone. Neither will any identifying data be disclosed or sold to any third party for any purpose. Data we collect through logging visits to our site (orginating IP, referral data, browser and platform type, traffic flows, geographical area of request, etc.) is only used in an aggregated form, which means we will not make any effort to identify users of Interaction-Design.org. The data is only used for server administration, fault finding, site improvement, etc. - as is done on most websites.

Aggregate (and thus completely non-identifying) statistics generated from these logs may be reported as part of research results or may be published on this site as a curiosity.

3. Cookies

Our sites may use cookies. This is often as a convenience for you to enable certain site features.

You may wish to clear these cookies and the browser cache if you wish to refrain from revealing any identifying information, especially if you are using a public or shared computer. You may also wish to disable your browser from accepting cookies.

4. Private logging

Any time you visit a page on the internet, you send quite a bit of information to the server. The webservers that host this site maintain access logs with the information that you send. This information is used to provide site statistics and to get an idea of popular pages and what sites link here. We do not intend to use these logs to identify legitimate users.

The data logged may be used by us to solve technical problems with the site and, in cases of abuse of this site, to investigate the abuse.

We also use web analytics services to get a general idea of the kinds of traffic our websites get in order to provide better services and to set benchmarks for how we are doing in meeting the OKFN's goals.

Again, if you are concerned about attempts to match your IP address to your identity, you may wish to use an anonymous browsing service or attempt some means to obfuscate your real IP address.

5. Data release policy

Our policy is only to release the data we collect in the following circumstances:

6. Public data and publishing

Browsing this site doesn't reveal your identity publicly, though see Private Logging later in this document for more information.

7. Author identification

When making contributions to this site (e.g. posting a comment, commentaries, editing a page in the wiki, etc), a name and email address may be required. You do not have to select your real name or use your regular email address. If you are concerned, you may wish to get a free email account or attempt to use a remail service.

Your activity on our website may be identified by your IP address. These numbers could potentially be traceable to identifying information about you, whether it is your home ISP or the University or Work account where the IP address is registered. Your IP address could potentially be used in conjunction with other data to identify you.

If you are concerned about attempts to match your IP address to your identity, you may wish to use an anonymous browsing service or attempt some means to obfuscate your real IP address.

If so, you might like to try Tor, an anonymous browsing service.

8. Information security

We make no guarantee that the information that you provide us will be secure.