Re: Representing ambiguity in datetime?
Ron Adam wrote: This is a very common problem in genealogy research as well as other sciences that deal with history, such as geology, geography, and archeology. .. So it seems using 0's for the missing day or month may be how to do it. Except of course humans like to make things more complicated than that. Some journals are published quarterly so an edition might be Jan-Mar. Some countries refer to week numbers, so an event might be in week 12. I offer no suggestions as to how to handle these cases. Andrew [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Representing ambiguity in datetime?
Ron Adam [EMAIL PROTECTED] writes: So it seems using 0's for the missing day or month may be how to do it. This doesn't allow more specific amounts of ambiguity. I suggest either a pair of dates, which represent the earliest and latest that the event could have been (and are equal if there is no ambiguity), or a date plus a number of days of uncertainty, i.e. 21 June 2005 +- 5 days. Dan -- http://mail.python.org/mailman/listinfo/python-list
Representing ambiguity in datetime?
What do you do when a date or time is incompletely specified? ISTM, that as it is, there is no formal way to store this --- you have to guess, and there's no way to indicate that the guess is different from solid information. As a result, I have sometimes had to abandon datetime, even though it seemed like the logical choice for representing data. E.g. I might have information like this paper was published in May 1997. There's no way to write that with datetime, is there? Even if I just use the date object instead of datetime, I still have to actually specify something like May 1, 1997 --- fabricating data, which is frequently undesireable (later on, I might find information saying that it was actually published May 23, 1997 and I might want to update the earlier one, or simply evaluate them as equal since they are, to within the precision given --- for example, I might be trying to decide that two database entries are really duplicate references to the same paper). I know that this is somewhat theoretically stated, but I have run into to concrete problems along the lines of the above. I'd say this is analogous to how you might use None rather than 0 to represent an integer if you don't know it's value (rather than knowing that it is zero). ISTM, you ought to be able to specify a date as, e.g.: d = datetime.date(2005, 5, None) I realize there might be some complexity with deciding how to handle datestamp math, but as this situation occurs frequently in real life, it seems like it shouldn't be avoided. How do other people deal with this kind of problem? Cheers, Terry -- Terry Hancock ( hancock at anansispaceworks.com ) Anansi Spaceworks http://www.anansispaceworks.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Representing ambiguity in datetime?
Terry Hancock wrote: What do you do when a date or time is incompletely specified? ISTM, that as it is, there is no formal way to store this --- you have to guess, and there's no way to indicate that the guess is different from solid information. As a result, I have sometimes had to abandon datetime, even though it seemed like the logical choice for representing data. E.g. I might have information like this paper was published in May 1997. There's no way to write that with datetime, is there? Even if I just use the date object instead of datetime, I still have to actually specify something like May 1, 1997 --- fabricating data, which is frequently undesireable (later on, I might find information saying that it was actually published May 23, 1997 and I might want to update the earlier one, or simply evaluate them as equal since they are, to within the precision given --- for example, I might be trying to decide that two database entries are really duplicate references to the same paper). I know that this is somewhat theoretically stated, but I have run into to concrete problems along the lines of the above. I'd say this is analogous to how you might use None rather than 0 to represent an integer if you don't know it's value (rather than knowing that it is zero). ISTM, you ought to be able to specify a date as, e.g.: d = datetime.date(2005, 5, None) I realize there might be some complexity with deciding how to handle datestamp math, but as this situation occurs frequently in real life, it seems like it shouldn't be avoided. How do other people deal with this kind of problem? It's not a problem I've had to deal with, but it seems that the simplest way to handle it would be to store the value as a datetime and a format. That way you can explicitly use 1 or 0 as a default (as appropriate) to create the datetime and then ensure it's represented only to the required degree of precision by using the supplied format. Don't know whether this will work for you, just a thought. regards Steve -- Steve Holden+1 703 861 4237 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ Python Web Programming http://pydish.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Representing ambiguity in datetime?
On Tue, 17 May 2005 17:38:30 -0500, Terry Hancock [EMAIL PROTECTED] wrote: What do you do when a date or time is incompletely specified? ISTM, that as it is, there is no formal way to store this --- you have to guess, and there's no way to indicate that the guess is different from solid information. As a result, I have sometimes had to abandon datetime, even though it seemed like the logical choice for representing data. E.g. I might have information like this paper was published in May 1997. There's no way to write that with datetime, is there? Even if I just use the date object instead of datetime, I still have to actually specify something like May 1, 1997 --- fabricating data, which is frequently undesireable (later on, I might find information saying that it was actually published May 23, 1997 and I might want to update the earlier one, or simply evaluate them as equal since they are, to within the precision given --- for example, I might be trying to decide that two database entries are really duplicate references to the same paper). I know that this is somewhat theoretically stated, but I have run into to concrete problems along the lines of the above. I'd say this is analogous to how you might use None rather than 0 to represent an integer if you don't know it's value (rather than knowing that it is zero). ISTM, you ought to be able to specify a date as, e.g.: d = datetime.date(2005, 5, None) I realize there might be some complexity with deciding how to handle datestamp math, but as this situation occurs frequently in real life, it seems like it shouldn't be avoided. How do other people deal with this kind of problem? Mostly, badly :-( Real-life example: due to war-time disruption etc, in some countries it is common enough to find that the date of birth of someone born in the 1940s is not known precisely. E.g. on the Hong Kong identity card, it is possible to find only the year and month of birth, and sometimes even only the year. Depending on the purpose, legislation and convention will take the first day of the vague period or the last day when a calculation is required. Badly == entering into a database the exact date that was used for the purpose du jour, with no indication that the source was vague. Consequently a person can have DOB recorded as 1945-01-01 on one database and 1945-12-31 on another. Suggested approach in Python (sketch): Don't try to get the datetime module to solve the problem. Define a fuzzydate class. Internal representation: I'd suggest earliest possible date and latest possible date. That way you have valid date instances for doing date arithmetic. May have different constructors depending on how the incoming vagueness is specified. HTH, John -- http://mail.python.org/mailman/listinfo/python-list
Re: Representing ambiguity in datetime?
John Machin wrote: On Tue, 17 May 2005 17:38:30 -0500, Terry Hancock [EMAIL PROTECTED] wrote: What do you do when a date or time is incompletely specified? ISTM, that as it is, there is no formal way to store this --- you have to guess, and there's no way to indicate that the guess is different from solid information. As a result, I have sometimes had to abandon datetime, even though it seemed like the logical choice for representing data. E.g. I might have information like this paper was published in May 1997. There's no way to write that with datetime, is there? Even if I just use the date object instead of datetime, I still have to actually specify something like May 1, 1997 --- fabricating data, which is frequently undesireable (later on, I might find information saying that it was actually published May 23, 1997 and I might want to update the earlier one, or simply evaluate them as equal since they are, to within the precision given --- for example, I might be trying to decide that two database entries are really duplicate references to the same paper). I know that this is somewhat theoretically stated, but I have run into to concrete problems along the lines of the above. I'd say this is analogous to how you might use None rather than 0 to represent an integer if you don't know it's value (rather than knowing that it is zero). ISTM, you ought to be able to specify a date as, e.g.: d = datetime.date(2005, 5, None) I realize there might be some complexity with deciding how to handle datestamp math, but as this situation occurs frequently in real life, it seems like it shouldn't be avoided. How do other people deal with this kind of problem? Mostly, badly :-( Real-life example: due to war-time disruption etc, in some countries it is common enough to find that the date of birth of someone born in the 1940s is not known precisely. E.g. on the Hong Kong identity card, it is possible to find only the year and month of birth, and sometimes even only the year. Depending on the purpose, legislation and convention will take the first day of the vague period or the last day when a calculation is required. Badly == entering into a database the exact date that was used for the purpose du jour, with no indication that the source was vague. Consequently a person can have DOB recorded as 1945-01-01 on one database and 1945-12-31 on another. Suggested approach in Python (sketch): Don't try to get the datetime module to solve the problem. Define a fuzzydate class. Internal representation: I'd suggest earliest possible date and latest possible date. That way you have valid date instances for doing date arithmetic. May have different constructors depending on how the incoming vagueness is specified. HTH, John This is a very common problem in genealogy research as well as other sciences that deal with history, such as geology, geography, and archeology. I agree that some standard way of dealing with fuzzy dates would be a good thing. I think looking at how others do it would be the way to start... A google search found the following reference buried in a long reference page on mysql. http://www.dreamlink.net/mysql/manual_Functions.html The reason the ranges for the month and day specifiers begin with zero is that MySQL allows incomplete dates such as '2004-00-00' to be stored as of MySQL 3.23. So it seems using 0's for the missing day or month may be how to do it. Cheers, _Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Representing ambiguity in datetime?
Hi All-- Ron Adam wrote: John Machin wrote: On Tue, 17 May 2005 17:38:30 -0500, Terry Hancock [EMAIL PROTECTED] wrote: What do you do when a date or time is incompletely specified? The reason the ranges for the month and day specifiers begin with zero is that MySQL allows incomplete dates such as '2004-00-00' to be stored as of MySQL 3.23. So it seems using 0's for the missing day or month may be how to do it. This is somewhat the approach I took in order to allow users to specify an incomplete Mayan date in order to list possibilities. But instead of 0 (which is a valid entry in most Mayan date components), I used None. The web version can be found at http://www.pauahtun.org/Calendar/tools.html (the Search for Matching Dates button) The paper describing the incomplete Mayan date tool is at: http://www.pauahtun.org/python_vuh.html Metta, Ivan -- Ivan Van Laningham God N Locomotive Works http://www.andi-holmes.com/ http://www.foretec.com/python/workshops/1998-11/proceedings.html Army Signal Corps: Cu Chi, Class of '70 Author: Teach Yourself Python in 24 Hours -- http://mail.python.org/mailman/listinfo/python-list
Re: Representing ambiguity in datetime?
Terry Hancock wrote: What do you do when a date or time is incompletely specified? Doesn't the answer to this pretty much entirely depend on how you are going to make use of the information? What are your use cases? -- http://mail.python.org/mailman/listinfo/python-list
