Hi Daphne, I think that anything that has to deal with vague temporal or spatial information will automatically turn out te be fairly complex.
The fuzzy endpoints of periods is probably the easier one. There the big hurdle is making a good UI that allows for people to enter vague temporal information in a simple and straightforward way that doesn't take to long. We've currently implemented this with a set of widget that allow choosing a start period and an end period whereby both can have different levels of fuzzyness. Eg. A period of time that runs from 'the 8th century BC' till the year 57 BC (Iron Age in Belgium). It's a very textual way of entering data, but that seems to match our users best. Although in actual fact we currently only use the Fuzzy Temporal Intervals for dates of "Events" (an excavation, a survey, aerial photography, ...) For dating of sites and monuments we use an entirely different approach based solely on a thesaurus of periods. I think the second direction: Allow periods and regions to be associated poses a lot more conceptual issues. I guess one could define a whole set of different "Iron Ages", but I have a hard time seeing how it would all work on a practical level. Especially once you start to factor in bringing together data from different implementations and the fact that a region can be vague as well. I also think that another complicating factor can be researches who tend take their chronological system with them. For example, in Flanders, a part of the Iron Age archaeologists use the French division of the Iron Age and another group uses the Dutch division. One group tends to work closer to the French border, the other one closer to the Dutch border. But they also seem to be aligned with the universities the archaeologists graduated from. So I'm not even sure anyone would be capable of geographically defining those ares. Also, when someone then tries to search for Late Iron Age, should they get results from the French Late Iron Age, the Dutch one or both? Or should it be impossible to search for something like 'Late Iron Age' and only possible to search for a specific one? I'm also not sure if the definition of a certain period in a certain area has stayed constant through time. That probably affects things as well. Anyway, it's an absolutely facinating research topic, but one where I think you really need to define a clear scope for your project and resist the tempation of going to far away from it. And make sure that you can communicate to users of your system which choices you've made and why. Cheers, Koen ________________________________________ Van: archesproject@googlegroups.com [archesproject@googlegroups.com] namens Daphne Ippolito [daphne...@gmail.com] Verzonden: zondag 16 maart 2014 20:08 Aan: archesproject@googlegroups.com Onderwerp: [Arches] Re: Ideas for GSoC Project: Improve Representation of Spatial-Temporal Relationships Hi. Thanks for your responses. I don't know Dutch, but your abstract did a good job of explaining what the situation is and the terminology I should be looking into. There seems to be two separate directions this project could go in. 1. Improving the way Arches deals with endpoints of periods by allowing for the input of fuzziness. This task doesn't have a spatial component to it. The project would involve implementing a way for users to specify uncertainty and subjectivity in their period definitions using the algorithms you mention in your post. 2. Creating the ability for periods to be spatially referenced. This task only deals with the spatial, not the temporal, definition of periods. It has two tiers of complexity. First, allow periods to be associated with geospatial regions. Second, devise a system to represent the fuzziness of these geospatial regions. I am not sure whether both can be tackled in one summer, or if I should pin my focus on one. Thanks for all the input. -Daphne On Sunday, 16 March 2014 05:10:07 UTC-4, Koen Van Daele wrote: Hi Daphne, I did some work on representing vague/imperfect temporal information in relational databases. It's a very interesting, but quite complicated subject. I did a masterpaper on it, but that's in Dutch. I don't suppose you speak Dutch? It does also contain an English abstract. You can find the masterpaper here: http://lib.ugent.be/fulltxt/RUG01/001/418/820/RUG01-001418820_2010_0001_AC.pdf. I did a conference paper on this subject at CAA 2012. You can find the slids here: http://www.slideshare.net/koenedaele/imperfect-temporal-information-in-data-sets. The digital paper should have been published by now, but the CAA publication process seems to be quite slow at the moment. The basic idea was to treat spans of time as fuzzy sets. I then implemented and tested a few different algorithms on actually reasoning with these fuzzy temporal intervals. The implementation consists of using postgis geometries for representing fuzy temporal intervals and PL/PGSQL functions for actually comparing them. I packaged the code as a library and released it under an MIT license on Github: https://github.com/koenedaele/pgFTI. Work has been done on porting one of the algorithms to a pure C based extension to postgresql for better performance (this would also remove the dependency on PostGIS). Still need to package that one up and release it to the public. I also recently gave a similar talk at the University of Paris about this subject that also listed some other ways of dealing with time in our databases. You can find the slides for this talk here: http://www.slideshare.net/koenedaele/paris2014. In that talk I also mention how we deal with periods and subperiods by using a thesaurus. I think this should be feasible with Arches as well. So, some of these might give you some ideas for dealing with the typical vagueness of temporal information inherent in archaeology. I never had to deal with the fact that one period can have different temporal borders in different parts of the world (where those parts are in themselves inherently vague as well). Seems like a tough nut to crack. I'll see if I can come up with any helpful suggestions on that topic. Cheers, Koen Op vrijdag 14 maart 2014 22:52:54 UTC+1 schreef Daphne Ippolito: Hello. Before I start writing my GSoC proposal, I wanted to share some of my initial thoughts on the project for improving Arches' representation of spatial-temporal relationships. The biggest conceptual difficulty I see in this task is that the geographical boundaries between periods are often grey. Either they are not clearly defined to begin with, or they are not entirely agreed upon by archaeologists. My initial implementation idea was to allow database managers to upload or draw polygons representing periods. Each polygon would have an associated period name and date interval. This information would be relatively simple to store in a database; however, I am a bit worried the format might be too rigid to represent complex spatial-temporal relationships. The "Brief Explanation" mentions periods like the Iron Age whose temporal endpoints vary in different geographical regions. Another problem that needs to be addressed is periods that correspond to both geographical and temporal boundaries. For example, suppose a database were to be set up representing the entire Middle East. The Pre-Pottery Neolithic A distinction makes sense for sites in the Fertile Crescent but would not be relevant to sites in the Sinai Peninsula. Situations like this will become increasingly prominent as Arches is applied to larger geographical regions. Here are some questions I have come up with relating to my idea of representing periods as dated polygons. 1. Should two polygons with the same period name (say, "Iron Age") be able to overlap? I don't think there is ever a situation where this makes sense. 2. Does a period need to be defined over all geographical space included in the database? This might make sense for regional map-databases, such as the Britain example, but it does not make as much sense for larger geographical areas, such as the entire Middle East. 3. How can the system deal with fuzzy temporal or geographical boundaries caused by disagreements between archaeologists or by the gradual spread of a period-defining technology or culture from one location to another? Ideally, there should be a way for users to browse periods and their geographical boundaries before doing a search. The simplest solution I can come up with would be to represent each period as a map layer that can be turned on and off just like the current map layers. When the polygons within the layer are clicked, they would give the dates for the period within that boundary. The user would then need two ways to search by period: 1. Search by a period and geographical region. 2. Search just by period, but by alerted that results may come from varying time intervals. I have an additional project proposal that could possibly be an extension of this one. It would be really nice if Arches supported the concept of sub-periods. For example, the Early, Middle, and Late Iron Age would be classified as sub-periods of an encompassing Iron Age period. Is there already support for something like this? In the Britain example, I can search for each of these distinctions, but the UI does not elucidate any sort of hierarchy between them. I would appreciate any feedback on these ideas and their feasibility within the current Arches system. While I've read through the User Guide and explored the example Britain implementation online, I haven't had much of a chance to get my hands dirty with the code yet. I'm looking forward to your comments. -Daphne -- -- To post, send email to archesproject@googlegroups.com. To unsubscribe, send email to archesproject+unsubscr...@googlegroups.com. For more information, visit https://groups.google.com/d/forum/archesproject?hl=en --- You received this message because you are subscribed to the Google Groups "Arches Project" group. To unsubscribe from this group and stop receiving emails from it, send an email to archesproject+unsubscr...@googlegroups.com<mailto:archesproject+unsubscr...@googlegroups.com>. For more options, visit https://groups.google.com/d/optout. -- -- To post, send email to archesproject@googlegroups.com. To unsubscribe, send email to archesproject+unsubscr...@googlegroups.com. For more information, visit https://groups.google.com/d/forum/archesproject?hl=en --- You received this message because you are subscribed to the Google Groups "Arches Project" group. To unsubscribe from this group and stop receiving emails from it, send an email to archesproject+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
