Chris,
I like this idea. Sheryl came up with the same thing independently (great
minds!) when we were talking offline.
Comments inline...
On Jan 18, 2012, at 1:26 PM, Mattmann, Chris A (388J) wrote:
> Hey Ricky,
>
> On Jan 18, 2012, at 10:27 AM, Nguyen, Ricky wrote:
>
>> Hi all,
>>
>> Suppose I wanted to store a list of episodes in metadata. An episode has 2
>> properties: start time and end time. I can think of 2 ways to do this:
>>
>> 1) use sub-metadata groups
>> <key>Episode/1/start</key>
>> <val>2011-01-15</val>
>> <key>Episode/1/end</key>
>> <val>2011-01-16</val>
>> <key>Episode/2/start</key>
>> <val>2011-01-17</val>
>> <key>Episode/2/end</key>
>> <val>2011-01-18</val>
>>
>> 2) declare length, and follow key patterns EpStartN and EpEndN
>> <key>NumEpisodes</key>
>> <val>2</val>
>> <key>EpStart1</key>
>> <val>2011-01-15</val>
>
> Here's another way that I think will help with what your intended use
> of the metadata is (to query for it in the PGE, for example).
>
> <keyval>
> <key>EpisodeStartDateTime</key>
> <val>2011-01-17</val>
> <val>2011-01-18</val>
> </keyval>
>
> <keyval>
> <key>EpisodeEndDateTime</key>
> <val>TBD</val>
> <val>TBD</val>
> </keyval>
>
> Then, you just make sure to encode a commensurate number of values
> together in each metadata field, then you can basically pick one of the
> fields to interrogate and do something like:
>
> Metadata met;
> List<String> startDateTimes = met.getAllMetadata("EpsidodeStartDateTime") !=
> null ?
> met.getAllMetadata("EpsidodeStartDateTime"):new Vector<String>();
> List <String> endDateTimes = met.getAllMetadata("EpsidodeEndDateTime") !=
> null ?
> met.getAllMetadata("EpsidodeEndDateTime"):new Vector<String>();
>
> for(int i=0; i < startDateTimes.size() ; i++){
> // i == the episodeNum?
> // if it isn't, then just store an associated EpisodeNum field with the
> same
> // size as the start/end date time
> String startDateTime = startDateTimes.get(i);
> String endDateTime = endDateTimes.get(i);
> }
>
> Does that help?
<key>NumEpisodes</key>
<val>2</val>
would help with this.
>
>>
>> So then the next question is, how do I write elements.xml (in FileMgr
>> policy) to accommodate the variable number of keys?
>
> No need it assumes that by default, since it's a NoSQL type store :)
+1. With your proposed metadata, the _keys_ are still be pre-defined in
elements.xml as NumEpisodes, EpisodeStartTime, EpisodeEndTime. But now the
_values_ are multi-valued lists which can grow as necessary.
A related question: is there a way to use dynamic metadata keys, or must all
keys be predefined in elements.xml ?
>
>>
>> And a follow up question is, how do I retrieve/use this information when
>> creating PGE config queries? (SQL(Format='$whatgoeshere') SELECT
>> whatgoeshere FROM …)
>
> You can query that way and you'll just get back all the values (delimited by
> ",") and concatenated together.
+1. Your proposed metadata is easily query-able.
>
> Cheers,
> Chris
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Chris Mattmann, Ph.D.
> Senior Computer Scientist
> NASA Jet Propulsion Laboratory Pasadena, CA 91109 USA
> Office: 171-266B, Mailstop: 171-246
> Email: [email protected]
> WWW: http://sunset.usc.edu/~mattmann/
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Adjunct Assistant Professor, Computer Science Department
> University of Southern California, Los Angeles, CA 90089 USA
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
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