Tag Archive for 'ogc'

WFS-T adventures with Mapinfo 9.5

So i’ve been a bit late taking a look at the new Mapinfo Professional v9.5. With the consistent dissapointment towards the consumption of OGC standards in commercial apps I wasn’t holding my breath … but wait a sec, it did work and it worked damn well. I mean, it worked flawlessly; updates, inserts, deletes, lock support and it also comes complete with a semi-intelligent conflict manager.

Mapinfo

A few more suggestions to improve things further (for anyone listening~) …

  1. Add HTTP compression handling. Huge performance gains with the transfer of features and its really a no brainer to enable in any http library.
  2. I am by no means a “Mapinfo Master” ™, but it would be great to enable an automated WFS Table refresh especially if you are retrieving features based on CURRENT_MAPPER.  I guess the CTRL+F5 shortcut makes it easy-ish … but i certainly found myself wondering whether i had retrieved the features or not and ended up just sending unnecessary requests.
  3. If a transaction is successful, give me some kind of alert. Alerting only when it fails does not instill much confidence whether my long edit session went through or not (even after refreshing)
  4. It would be fantastic to add helpful warning messages when performance drops. I’d imagine most users would skim over the maxfeatures and column / row filters and just add the layer.
  5. If the first request takes 5 minutes and Mapinfo tells me i just retrieved 4000 poly features totalling 10mb and it kindly directed me to the WFS how-to, i’d be more inclined to see what the filtering options were all about :)

So there’s no WFS1.1 support … but i’m still trying to get my head around handling the axis order issue and are more than happy to let sleeping dogs lie … at least for the moment. I only had time to test against our Geoserver installs, but it certainly seems tested against many other apps including Cadcorp, Ionic & Mapinfo. Geoserver specific here, but the advanced security in 1.6.x works very well with the bundled support for basic authentication.

Finally…

Where art thou WCS clients?

How can I push a proposal for provisioning elevation data via Web Coverage Services when there are no freakin’ clients?

After a couple of hours I seriously only found,

Suggesting users manually craft the requests is not an option :)

I guess this kinda gets back to my previous rants on this issue. We’ve got Deegree, Geoserver, Mapserver and quite a few other notable suppliers pushing coverages out … to where exactly??

Image courtesy http://www.refractions.net/terrainserver/

It seems absurd how many people grab the whole SRTM/Landsat/DEMs in general just because “its easier”. After looking into WCS, perhaps they are right. Chicken meet egg, again.

From the other side of the fence …

Like all good arguments, there are other sides. In what seems to be a two part OGC mini-series on Charlie Savage’s blog RE: problems with the OGC, I noticed a comment by Shane asking …

I’m surprised at the lack of outburst by the pro-standards community. This makes me think they are humbled by your views. I’d expect somebody out there to stick up for OGC and the other standards you mentioned. It would be intriguing to hear someone from DM Solutions or Ionic, for instance.

Even though i am not Ionic, DMsolutions … here are some thoughts from someone who thinks the OGC has created some pretty darned useful standards.

A retort to one of Charlie’s post if you will .. :)

Rendering Maps. The argument i often see with the WMS bashing goes something like, “WMS is slow. Who uses it in an Enterprise architecture. G/Y/M dont use it, therefore by my intelligent calculations, WMS must be useless”. Lets back up a second. If you want a high performance, slippy interface that can be easily cached, tiling is certainly your best bet. I get the distinct feeling that a lot of people forget the disadvantages of a tiled mapping cache,

  1. Fixed scales. The amount of people i see who simply generate their zoom levels based on GMaps is crazy. What about what your users want? If there are any papers detailing why splitting the world into 18 distinct zoom levels is ideal, please tell me. I’m yet to find one. One size will never fit all.
  2. Redundant data storage. Active caching mechanisms whereby caches are only populated once browsed is nifty, but it also negates somewhat the advantage of using a cache. Conversely, if you pregenerate your entire cache you are more than likely storing 80% (number plucked from the sky) more data than you need. We also arent even touching the storage of the source data either here, or considering the time required to maintain the cache when you are using volatile datasets.
  3. Lack of integration across clients. The whole benefit of standards it to enable cross-use, cross-communication amongst clients and servers. This is non evident amongst tile servers (beyond of course worldkit and openlayers). Sure, WMS-C / TMS are hopefully gathering steam at the moment, but if you are considering integration right now across a gamut of applications, nothing is better than WMS for transferring maps over the interweb to multiple clients. People seem to be losing sight of this purpose every day.
  4. And the kicker for me … Absolutely no customisation. Dont want that road layer? You better hope they duplicated the cache and removed them otherwise you’re in trouble. Want the map in a useful cartographic projection? Duplicate again! Hmmm, can you colour the cadastre yellow instead of red? No, but i can duplicate the cache again for you. I could go on, but you should get the idea ..

And finally, “Arbitrary bounding boxes” are your friends Mr Charlie! Let your users decide their output scale, not the magical we-chose-18-scales-coz-google-wanted-a-nice-single-square-tile-at-zoom-level-0 :)

Summing up, WMS is your friend regardless. Don’t toss it out with the bathwater just because you are using a cache with a slippy map. Implementing WMS and whatever tiling scheme you can easily abstract *AROUND* WMS will give you and your users the best of both worlds. The fact that you can quite easily use any random WMS server inside a tiling scheme surely highlights that the standard does have flexibility.

Time is at a premium at the moment so i wont reply to all Charlie’s points (especially sharing data because we could be here forever). All in all i can see his point of view however we need to remember that we can only work with what we have at the moment, despite their flaws. GeoRSS/Atom/OWS Context/KML ratifying are all coming, its just up to the rest of us to pick up the ball and keep running with it so this will never be true again,

Web mapping standards are going through a transitional state and haven’t kept up with GIS technology breakthroughs over the last few years.

Chris.

WFS Feature paging … yes please

Sean posted his thoughts in response to Chris’ and all i can say is, yes please!

My random thoughts,

  • Why this functionality was never embedded into WFS i will never know. After playing with CSW for the last 6 months where similar “pagination” is available … it just makes sense. How the average Jo Blogs will ever understand what maxFeatures should be set to is irrelevant if the user cannot even determine how many *total* features are available given his query. OGC CS-W handles this quite nicely, almost identical to how Chris H. described it. If i search for “hydro”, it will give me a numberOfRecordsMatched=”340″ but then also tell me that i’m just viewing the first 10 records.
<csw version="2.0.0" service="csw" maxrecords="10" startposition="1"></csw>
  • Paging has been linked to server performance, particularly caching a set number of features. This imo, would only hold true if the given features are retrieved in the same manner. How this would handle filters i’m a little unsure of (beyond the simple bbox). Just because search engines index http://sigma.openplans.org/geoserver/water_shorelines/100 doesn’t mean that the same features will appear in the same page 10 days later, for example. Checksum? HTTP Last-modified? *shrug*

Looks like i need to pay more attention to the OGC boards :)

Taking it to “the man”

Paul has graciously asked people to send him some queries to raise before the OGC technical meeting in Ottawa. In somewhat of an irony, it has been exactly 7 months to the day that my rant on client support was first posted.

Unfortunately my post still stands. To reiterate my point,

While i understand the importance of server compliance using tools such as CITE, if the subsequent clients consuming these services are poorly implemented, the end user surely has to question the point of it all.

It should be all about the clients baby! Unfortunately outside of the OWS-X and other demonstrator projects around the globe (where arguably the roles are clearly defined), vendor support is more or less a waste of time. What can be done in one application can’t be done in another. Seemingly simple items of the specs are broken, poorly implemented or simply forgotten. Vendors are all to quick to leap to the conclusion that their *insert propriety acronym here* could solve the problem, even though its entirely feasible to use the standards if their product simply supported it better. Oh and lets not forget that the product leaf-let clearly states that the protocol is supported … but by how much? Who knows!

I think the following image sums up my feelings nicely, we need one of these …

yardstick.gif

Whether or not WMS/WFS/WCS/CSW (…) client support is caused by a lack of motivation, client demand or vendor negligence, i won’t go so far as to guess. Certainly if OGC put as much emphasis on broadening the consumption of its standard’s as it does jumping through hoops to get certified, I would have a lot less grief at work!

“I’m sorry “Frustrated-Consumer-of-OGC-standards”, what you have requested is entirely possible with the standards and server however your client does not support that manner of request. Can i advise hand-coding a *insert language here* script to post a request, parse the response, convert the format and then drop it into your GIS so you can do what you have asked??”

“Can you just send me the file? That will be easier …”

I hope the horrible analogy of build it and they will come will hold true. Otherwise, we’re in trouble …