Offline HTML5, Chrome, and infinite regress

Posted on October 7, 2012 by alan

I am using HTML5’s offline mode as part of the Tiree Mobile Archive project.

This is, in principle, a lovely way of creating web sites that behave pretty much like native apps on mobile devices. However, things, as you can guess, do not always go as smoothly as the press releases and blogs suggest!

Some time I must write at length on various useful lessons, but, for now, just one – the potential for an endless cycle of caches, rather like Jörmungandr, the Norse world serpent, that wraps around the world swallowing its own tail.

My problem started when I had a file (which I will call ‘shared.prob’ below, but was actually ‘place_data.js’), which I had updated on the web server, but kept showing an old version on Chrome no matter how many times I hit refresh and even after I went to the history settings and asked chrome to empty its cache.

I eventually got to the bottom of this and it turned out to be this Jörmungandr, cache-eats-cache, problem (browser bug!), but I should start at the beginning …

To make a web site work off-line in HTML5 you simply include a link to an application cache manifest file in the main file’s <html> tag. The browser then pre-loads all of the files mentioned in the manifest to create the application cache (appCache for short). The site is then viewable off-line. If this is combined with off-line storage using the built-in SQLite database, you can have highly functional applications, which can sync to central services using AJAX when connected.

Of course sometimes you have updated files in the site and you would like browsers to pick up the new version. To do this you simply update the files, but then also update the manifest file in some way (often updating a version number or date in a comment). The browser periodically checks the manifest file when it is next connected (or at least some browsers check themselves, for some you need to add Javascript code to do it), and then when it notices the manifest has changed it invalidates the appCache and rechecks all the files mentioned in the manifest, downloading the new versions.

Great, your web site becomes an off-line app and gets automatically updated 🙂

Of course as you work on your site you are likely to end up with different versions of it. Each version has its own main html file and manifest giving a different appCache for each. This is fine, you can update the versions separately, and then invalidate just the one you updated – particularly useful if you want a frozen release version and a development version.

Of course there may be some files, for example icons and images, that are relatively static between versions, so you end up having both manifest files mentioning the same file. This is fine so long as the file never changes, but, if you ever do update that shared file, things get very odd indeed!

I will describe Chrome’s behaviour as it seems particularly ‘aggressive’ at caching, maybe because Google are trying to make their own web apps more efficient.

First you update the shared file (let’s call it shared.prob), then invalidate the two manifest files by updating them.

Next time you visit the site for appCache_1 Chrome notices that manifest_1 has been invalidated, so decides to check whether the files in the manifest need updating. When it gets to shared.prob it is about to go to the web to check it, then notices it is in appCache_2 – so uses that (old version).

Now it has the old version in appCache_1, but thinks it is up-to-date.

Next you visit the site associated with appCache_2, it notices manifest_2 is invalidated, checks files … and, you guessed it, when it gets to shared.prob, it takes the same old version from appCacche_1 🙁 🙁

They seem to keep playing catch like that for ever!

The only way out is to navigate to the pseudo-url ‘chrome://appcache-internals/’, which lets you remove caches entirely … wonderful.

But don’t know if there is an equivalent to this on Android browser as it certainly seems to have odd caching behaviour, but does seem to ‘sort itself out’ after a time! Other browsers seem to temporarily have problems like this, but a few forced refreshes seems to work!

For future versions I plan to use some Apache ‘Rewrite’ rules to make it look to the browser that the shared files are in fact to completely different files:

RewriteRule  ^version_3/shared/(.*)$   /shared_place/$1 [L]

To be fair the cache cycle more of a problem during development rather than deployment, but still … so confusing.

Useful sites:

These are some sites I found useful for the application cache, but none sorted everything … and none mentioned Chrome’s infinite cache cycle!

http://www.w3.org/TR/2008/WD-html5-20080122/#appcache
The W3C specification – of course this tell you how appCache is supposed to work, not necessarily what it does on actual browsers!
http://www.html5rocks.com/en/tutorials/appcache/beginner/
It is called “A Beginner’s Guide to using the Application Cache”, but is actually pretty complete.
http://appcachefacts.info
Really useful quick reference, but: “FACT: Any changes made to the manifest file will cause the browser to update the application cache.” – don’t you believe it! For some browsers (Chrome, Android) you have to add your own checks in the code (See “Updating the cache” section in “A Beginner’s Guide …”).).
http://manifest-validator.com/
Wonderful on-line manifest file validator checks both syntax and also whether all the referenced files download OK. Of course it cannot tell whether you have included all the files you need to.

a radical design for mobile telephony

Posted on August 2, 2012 by alan

We are all aware of the phenomenal growth in smartphone and tablet use. However, these are often designed with the needs of media and internet access above plain telephony. Touch screens do not have tactile feedback leading to mistyping, especially problematic when using touchtone-based phone services, for tablets especially, the form factor is far from optimal, … and try answering your phone call quickly by sliding your finger across the screen!

There are solutions. A recent gigaom post “Here’s why tablets (yes, tablets!) will replace the smartphone” suggested that hands-free headsets were already common, hence reducing the brick-to-the-ear effect. This of course does not deal with the key pad, but there are some solutions to this using the vibrator motor to give simulated tactile feedback, and various technologies are in development that will (in time) allow tactile features to be programmed onto the screen (e.g. see “Mobile tactile tech gets physical“).

Over a slightly longer time frame we can expect smart materials to develop to the point that concept pieces such as Fabian Hemmert’s Shape-Changing Mobiles will become possible. Instead of being a fixed shape not only will your tablet screen be able to develop solid buttons of all shapes on demand, but will potentially become travel mug, long-haul flight pillow or angle grinder.

The trouble is that not only are such technologies some years off, they are also tinkering at the edges, attempting to fix piecemeal some of the fundamental flaws of smartphone and tablet technology when it comes to telephony. Clearly a more radical approach is required.

While Bluetooth headsets are effective, they tend to suggest call centre rather than cool, a single device would be preferable. In addition this should ideally include some form of miniature key pad to facilitate typing telephone numbers (more extensive tasks such as address book management can be performed on the full-size tablet screen, especially if this is augmented with tactile feedback). Furthermore, for times when it is inconvenient to carry your full size tablet and it is in your handbag, rucksack or its custom wheelie bag, the perfect telephony attachment should also have a small additional screen to view the number you are dialing.

As a result of extensive research into user needs and in the spirit of the information appliance, the single purpose device optimised for a a single purpose, I have devised the perfect device: small, yet not too small to be lost, pocket sized so that it can be easily accessed when you receive a call, tactile, exploiting the deep understanding of the physicality community and knowledge from writing TouchIT. It will connect via Bluetooth to your existing smartphone/tablet and of course via WiFi or (in premium models) using 3G/GSM direct to mobile networks if you accidentally leave your smartphone at home.

I plan to demonstrate my early prototype at the forthcoming Physicality 2012 workshop, where Fabian will be giving a keynote.

Tiree going mobile

Posted on June 7, 2012 by alan

Tiree’s Historical Centre An Iodhlann has just been awarded funding by the Scottish Digital Research and Development Fund for Arts and Culture to make historic archive material available through a mobile application whilst ‘on the ground’ walking, cycling or driving around the island.

I’ve been involved in bigger projects, but I can’t recall being more excited than this one: I think partly because it brings together academic interests and local community.

the project

An Iodhlann (Gaelic for a stackyard) is the historical centre on the island of Tiree. Tiree has a rich history from the Mesolithic period to the Second World war base. The archive was established in 1998, and its collection of old letters, emigrant lists, maps, photographs, stories and songs now extends to 12 000 items. 500 items are available online, but the rest of the primary data is only available at the centre itself. A database of 3200 island place names collated by Dr Holliday, the chair of An Iodhlann, has recently been made available on the web at tireeplacenames.org. Given the size of the island (~750 permanent residents) this is a remarkable asset.

To date, the online access at An Iodhlann is mainly targeted at archival / historical use, although the centre itself has a more visitor-centred exhibition. However, the existing digital content has the potential to be used for a wider range of applications, particularly to enhance the island experience for visitors.

Over the next nine months we will create a mobile application allowing visitors and local historians to access geographically pertinent information, including old photographs, and interpretative maps/diagrams, while actually at sites of interest. This will largely use visitors’ own devices such as smart phones and tablets. Maps will be central to the application, using both OS OpenData and bespoke local maps and sketches of historical sites.

As well as adding an extra service for those who already visit An Iodhlann, we hope that this will attract new users, especially younger tourists. In addition a ‘data layer’ using elements of semantic web technology will mean that the raw geo-coded information is available for third parties to mash-up and for digital humanities research.

the mouse that roars

The Scottish Digital Research and Development Fund for Arts and Culture is run by Nesta, Creative Scotland and the Arts and Humanities Research Council (AHRC).

This was a highly competitive process with 52 applications of which just 6 were funded. The other successful organisations are: The National Piping Centre, Lyceum Theatre Company and the Edinburgh Cultural Quarter, Dundee Contemporary Arts, National Galleries of Scotland, Glasgow Film Theatre and Edinburgh Filmhouse. These are all big city organisations as were the projects funded by an earlier similar programme run by Nesta England.

As the only rural-based project, this is a great achievement for Tiree and a great challenge for us over the next nine months!

challenges

In areas of denser population or high overall tourist numbers, historical or natural sites attract sufficient visitors to justify full time (volunteer or paid) staff. In more remote rural locations or small islands there are neither sufficient people for volunteers to cover all, or even a significant number, of sites, nor have they sufficient tourist volume to justify commercial visitor centres.

A recent example of this on Tiree is the closing of the Thatched Cottage Museum. This is one of the few remaining thatched houses on the island, and housed a collection of everyday historical artefacts. This was owned by the Hebridean Trust, and staffed by local volunteers, but was recently closed and the building sold, as it proved difficult to keep it staffed sufficiently given the visitor numbers.

At some remote sites such as the Tiree chapels, dating back to the 10th century, or Iron Age hill forts, there are simple information boards and at a few locations there are also fixed indoor displays, including at An Iodhlann itself. However, there are practical and aesthetic limits on the amount of large-scale external signage and limits on the ongoing running and maintenance of indoor exhibits. Furthermore, limited mobile signals mean that any mobile-based solutions cannot assume continuous access.

from challenge to experience

Providing information on visitors’ own phones or tablets will address some of the problems of lack of signage and human guides. However, achieving this without effective mobile coverage means that simple web-based solutions will not work.

The application used whilst on the ground will need to be downloaded, but then this limits the total amount of information that is available whilst mobile; our first app will be built using HTML5 to ensure it will be available on the widest range of mobile devices (iOS, Android, Windows Mobile, ordinary laptops), but using HTML5 further reduces the local storage available¹.

In order to deal with this, the on-the-ground experience will be combined with a web site allowing pre-trip planning and post-trip reminiscence. This will also be map focused, allowing visitors to see where they have been or are about to go, access additional resources, such as photos and audio files that are too large to be available when on the ground (remembering poor mobile coverage). This may also offer an opportunity to view social content including comments or photographs of previous visitors and then to associate one’s own photographs taken during the day with the different sites and create a personal diary, which can be shared with others.

On reflection, this focus on preparation and reminiscence will create a richer and more extended experience than simply providing information on demand. Rather than reading reams of on-screen text whilst looking at a monument or attempting to hear an audio recording in the Tiree wind, instead visitors will have some information available in the field and more when they return to their holiday base, or home².

For some reason HTML5 applications are restricted to a maximum of 5Mb![back]
This is another example of a lesson I have seen so many times before: the power of constraints to force more innovative and better designs. So many times I have heard people say about their own designs “I wanted to make X, but couldn’t for some reason so did Y instead” and almost every time it is the latter, the resource-constrained design, that is clearly so much better.[back]

hyperreal tactile iPad keyboard

Posted on July 20, 2011 by alan

The soft keyboards on iPhone and iPad are surprisingly good. On the iPad I am finding my 3 finger typing almost as fast as on a physical keyboard … although a little more error prone as I keep mis-hitting the space bar and getting ‘n’ or ‘b’ instead (as inmthis shortbphrasemi am typing now), which the poor spell corrector can’t manage at all.

Of course if ou are a touch typist things may be different.

I was especially struck by the image of the keyboard on the iPad, which on the ‘F’ and ‘J’ keys has an image of the tiny tactile bar that allows easy finger positioning by touch alone. However, this is of course a flat screen and I am feeling I am in some sort of surreal world.

F key on iPad showing 'tactile' image

Italian conferences: PPD10, AVI2010 and Search Computing

Posted on June 5, 2010 by alan

I got back from trip to Rome and Milan last Tuesday, this included the PPD10 workshop that Aaron, Lucia, Sri and I had organised, and the AVI 2008 conference, both in University of Rome “La Sapienza”, and a day workshop on Search Computing at Milan Polytechnic.

PPD10

The PPD10 workshop on Coupled Display Visual Interfaces¹ followed on from a previous event, PPD08 at AVI 2008 and also a workshop on “Designing And Evaluating Mobile Phone-Based Interaction With Public Displays” at CHI2008. The linking of public and private displays is something I’ve been interested in for some years and it was exciting to see some of the kinds of scenarios discussed at Lancaster as potential futures some years ago now being implemented over a range of technologies. Many of the key issues and problems proposed then are still to be resolved and new ones arising, but certainly it seems the technology is ‘coming of age’. As well as much work filling in the space of interactions, there were also papers that pushed some of the existing dimensions/classifications, in particular, Rasmus Gude’s paper on “Digital Hospitality” stretched the public/private dimension by considering the appropriation of technology in the home by house guests. The full proceedings are available at the PPD10 website.

AVI 2010

AVI is always a joy, and AVI 2010 no exception; a biennial, single-track conference with high-quality papers (20% accept rate this year), and always in lovely places in Italy with good food and good company! I first went to AVI in 1996 when it was in Gubbio to give a keynote “Closing the Loop: modelling action, perception and information“, and have gone every time since — I always say that Stefano Levialdi is a bit like a drug pusher, the first experience for free and ever after you are hooked! The high spot this year was undoubtedly Hitomi Tsujita‘s “Complete fashion coordinator”², a system for using social networking to help choose clothes to wear — partly just fun with a wonderful video, but also a very thoughtful mix of physical and digital technology.

images from Complete Fashion Coordinator

The keynotes were all great, Daniel Keim gave a really lucid state of the art in Visual Analytics (more later) and Patrick Lynch a fresh view of visual understanding based on many years experience and highlighting particularly on some of the more immediate ‘gut’ reactions we have to interfaces. Daniel Wigdor gave an almost blow-by-blow account of work at Microsoft on developing interaction methods for next-generation touch-based user interfaces. His paper is a great methodological exemplar for researchers combining very practical considerations, more principled design space analysis and targeted experimentation.

Looking more at the detail of Daniel’s work at Microsoft, it is interesting that he has a harder job than Apple’s interaction developers. While Apple can design the hardware and interaction together, MS as system providers need to deal with very diverse hardware, leading to a ‘least common denominator’ approach at the level of quite basic touch interactions. For walk-up-and use systems such as Microsoft Surface in bar tables, this means that users have a consistent experience across devices. However, I did wonder whether this approach which is basically the presentation/lexical level of Seeheim was best, or whether it would be better to settle at some higher-level primitives more at the Seeheim dialog level, thinking particularly of the way the iPhone turns pull down menus form web pages into spinning selectors. For devices that people own it maybe that these more device specific variants of common logical interactions allow a richer user experience.

The complete AVI 2010 proceedings (in colour or B&W) can be found at the conference website.

The very last session of AVI was a panel I chaired on “Visual Analytics: people at the heart of data” with Daniel Keim, Margit Pohl, Bob Spence and Enrico Bertini (in the order they sat at the table!). The panel was prompted largely because the EU VisMaster Coordinated Action is producing a roadmap document looking at future challenges for visual analytics research in Europe and elsewhere. I had been worried that it could be a bit dead at 5pm on the last day of the conference, but it was a lively discussion … and Bob served well as the enthusiastic but also slightly sceptical outsider to VisMaster!

As I write this, there is still time (just, literally weeks!) for final input into the VisMaster roadmap and if you would like a draft I’ll be happy to send you a PDF and even happier if you give some feedback 🙂

Search Computing

I was invited to go to this one-day workshop and had the joy to travel up on the train from Rome with Stu Card and his daughter Gwyneth.

The search computing workshop was organised by the SeCo project. This is a large single-site project (around 25 people for 5 years) funded as one of the EU’s ‘IDEAS Advanced Grants’ supporting ‘investigation-driven frontier research’. Really good to see the EU funding work at the bleeding edge as so many national and European projects end up being ‘safe’.

The term search computing was entirely new to me, although instantly brought several concepts to mind. In fact the principle focus of SeCo is the bringing together of information in deep web resources including combining result rankings; in database terms a form of distributed join over heterogeneous data sources.

The work had many personal connections including work on concept classification using ODP data dating back to aQtive days as well as onCue itself and Snip!t. It also has similarities with linked data in the semantic web word, however with crucial differences. SeCo’s service approach uses meta-descriptions of the services to add semantics, whereas linked data in principle includes a degree of semantics in the RDF data. Also the ‘join’ on services is on values and so uses a degree of run-time identity matching (Stu Card’s example was how to know that LA=’Los Angeles’), whereas linked data relies on URIs so (again in principle) matching has already been done during data preparation. My feeling is that the linking of the two paradigms would be very powerful, and even for certain kinds of raw data, such as tables, external semantics seems sensible.

One of the real opportunities for both is to harness user interaction with data as an extra source of semantics. For example, for the identity matching issue, if a user is linking two data sources and notices that ‘LA’ and ‘Los Angeles’ are not identified, this can be added as part of the interaction to serve the user’s own purposes at that time, but by so doing adding a special case that can be used for the benefit of future users.

While SeCo is predominantly focused on the search federation, the broader issue of using search as part of algorithmics is also fascinating. Traditional algorithmics assumes that knowledge is basically in code or rules and is applied to data. In contrast we are seeing the rise of web algorithmics where knowledge is garnered from vast volumes of data. For example, Gianluca Demartini at the workshop mentioned that his group had used the Google suggest API to extend keywords and I’ve seen the same trick used previously³. To some extent this is like classic techniques of information retrieval, but whereas IR is principally focused on a closed document set, here the document set is being used to establish knowledge that can be used elsewhere. In work I’ve been involved with, both the concept classification and folksonomy mining with Alessio apply this same broad principle.

The slides from the workshop are appearing (but not all there yet!) at the workshop web page on the SeCo site.

yes I know this doesn’t give ‘PPD’ this stands for “public and private displays”[back]
Hitomi Tsujita, Koji Tsukada, Keisuke Kambara, Itiro Siio, Complete Fashion Coordinator: A support system for capturing and selecting daily clothes with social network, Proceedings of the Working Conference on Advanced Visual Interfaces (AVI2010), pp.127–132.[back]
The Yahoo! Related Suggestions API offers a similar service.[back]

an end to tinkering? are iPhones the problem

Posted on April 30, 2010 by alan

Thanks to @aquigley for tweeting about the silicon.com article “Why the iPhone could be bad news for computer science“. The article quotes Robert Harle from the Computer Laboratory at Cambridge worrying that the iPhone (and other closed platforms) are eroding the ability to ‘tinker’ with computers and so destroying the will amongst the young to understand the underlying technology.

I too have worried about the demise of interest not just in computers, but in science and technology in general. Also, the way Apple exercise almost draconian control over the platform is well documented (even rejecting an eBook application for fear it could be used to read the Karma Sutra!).

However, is the problem the closedness of the platform? On the iPhone and other smartphones, it is the apps that catch imagination and these are ‘open’ in the sense that it is possible to programme your own. Sure Apple charge for the privilege (why – the income surely can’t be major!), but it is free in education. So what matters, app development, is open … but boy is it hard to get started on the iPhone and many platforms.

It is not the coding itself, but the hoops you need to go through to get anything running, with multiple levels of ritual incantations. First you need to create a Certificate signing request to get Development certificate and a Provisioning profile based on your Device ID … sorry did I lose you, surely not you haven’t even written a line of code yet, for that you really need to understand the nib file … ooops I’ve lost the web page where I read how to do that, wait while I search the Apple Developer site …

Whatever happened to:

10 print "hello world"

This is not just the iPhone, try building your first Facebook app, … or if you are into open standards X Windows!

Nigel Davies said his 7 year old is just starting to code using Scratch. I recall Harold Thimbleby‘s son, now an award winning Mac developer similarly starting using Hypercard.

If we would like a generation of children enthused by Facebook and the iPhone, to become the next generation of computer scientists, then we need to give them tools to get started as painless and fun as these.

not quite everywhere

Posted on January 28, 2010 by alan

I’ve been (belatedly) reading Adam Greenfield‘s Everyware: The Dawning Age of Ubiquitous Computing. By ‘everywhere’ he means the pervasive insinuation of inter-connected computation into all aspects of our lives — ubiquitous/pervasive computing but seen in terms of lives not artefacts. Published in 2006, and so I guess written in 2004 or 2005, Adam confidently predicts that everywhere technology will have “significant and meaningful impact on the way you live your life and will do so before the first decade of the twenty-first century is out“, but one month into 2010 and I’ve not really noticed yet. I am not one of those people who fill their house with gadgets, so I guess unlikely to be an early adopter of ‘everywhere’, but even in the most techno-loving house at best I’ve seen the HiFi controlled through an iPhone.

Devices are clearly everywhere, but the connections between them seem infrequent and poor.

Why is ubiquitous technology still so … well un-ubiquitous?

Continue reading →

reading barcodes on the iPhone

Posted on December 22, 2009 by alan

I was wondering about scanning barcodes using the iPhone and found that pic2shop (a free app) lets third part iPhone apps and even web pages access its scanning software through a simply URL scheme interface.

Their developer documentation has an example iPhone app, but not an example web page. However, I made a web page using their interface in about 5 minutes (see PHP source of barcode reader).

If you have an iPhone you can try it out and scan a bar code now, although you need to install pic2shop first (but it is free).

By allowing third party apps to use their software they encourage downloads of their app, which will bring them revenue through product purchases. Through free giving they bring themselves benefit; a good open access story.

Apple’s Model-View-Controller is Seeheim

Posted on December 19, 2009 by alan

Just reading the iPhone Cocoa developer docs and its description of Model-View-Controller. However, if you look at the diagram rather than the model component directly notifying the view of changes as in classic MVC, in Cocoa the controller acts as mediator, more like the Dialogue component in the Seeheim architecture¹ or the Control component in PAC.

The docs describing the Cocoa MVC design pattern in more detail in fact do a detailed comparison with the Smalltalk MVC, but do not refer to Seeheim or PAC, I guess because they are less well known now-a-days. Only a few weeks ago when discussing architecture with my students, I described Seeheim as being more a conceptual architecture and not used in actual implementations now. I will have to update my lectures – Seeheim lives!

Shocked to find no real web documentation for Seeheim, not even on Wikipedia; looks like CS memory is short. However, it is described in chapter 8 of the HCI book and in the chapter 8 slides[back]

Christmas tree