Recently Freebase added flags for values: Has No Values and Has Unknown Values. If I query a property's value it will give me null if it is empty or has one of these flags. How do I determine if the value really is empty or if it's flagged?
A good place to find out about something that you see on freebase.com is the source code that drives the site. In particular, for this case:
https://code.google.com/p/freebase-site/source/browse/trunk/www/lib/propbox/js/propbox-edit.js#640
The properties that you need to query are:
/freebase/valuenotation/has_no_value
/freebase/valuenotation/has_value
Here's an example:
https://www.freebase.com/m/05r3dj?links&lang=en&filter=%2Ffreebase%2Fvaluenotation%2Fhas_value
Related
I'm trying to create a shacl based on the ontology that my organization is developing (in dutch): https://wegenenverkeer.data.vlaanderen.be/
The objects described have attributes (properties), that have a specified datatype. The datatype can a primitive (like string or decimal) or complex, which means the property will have properties itself (nested properties). For example: an asset object A will have an attribute assetId which is a complex datatype DtcIdentificator, which consists of two properties itself. I have succesfully created a shacl that validates objects by creating multiple shapes and nesting them.
I now run into the problem of what we call union datatypes. These are a special kind of complex datatypes. They are still nested datatypes: the attribute with the union datatypes will have multiple properties but only exactly zero or one of those properties may have a value. If the attribute has 2 properties with values, it is invalid. How can I create such a constraint in shacl?
Example (in dutch): https://wegenenverkeer.data.vlaanderen.be/doc/implementatiemodel/union-datatypes/#Afmeting%20verkeersbord
A traffic sign (Verkeersbord, see https://wegenenverkeer.data.vlaanderen.be/doc/implementatiemodel/signalisatie/#Verkeersbord) can have a property afmeting (size) of the datatype DtuAfmetingVerkeersbord.
If an asset A of this type would exist, I could define its size as (in dotnotation):
A.afmeting.rond.waarde = 700
-or-
A.afmeting.driehoekig.waarde = 400
Both are valid ways of using the afmeting property, however, if they are both used for the same object, this becomes invalid, as only one property of A.afmeting may have a value.
I have tried using the union constraint in shacl, but soon found out that that has nothing to do with what we call "union datatypes"
I think the reason you are struggling is because this kind of problem is usually modelled differently. Basically you have different types of Traffic signs and these signs can have measurements. With the model as you described, A.afmeting.rond.waarde captures 2 ideas using 1 property: (a) the type and (b) the size. From your question, this seems to be the intend. However, this is usually not how this kind of problem is addressed.
A more intuitive design is for Traffic sign to have 2 different properties: (a) type and (b) a measurement. The Traffic sign types are achthoekig, driehoekig, etc. Then you can use SHACL to check that a traffic sign has either both or no properties for a traffic sign.
I would like to have one field appear conditionally based on the value of another. How should I go about achieving this in dexterity?
E.g. One field is a boolean: Is the resource for sale?
If this is set as "yes" I'd like the next field to show up, being an integer- the price of the resource.
If I had to guess, I'd start hacking a javascript solution but I'm assuming there is a technique for doing it in an organised manner, but I can't find anything.
I should also mention that I am doing this to simplify the process of searching through this content later (using eea.facetednav) in which I don't know how to have a boolean search interface return results based on if the integer is > 0.
I am constructing a multipart message in construct shape. That message has a body part with distinguished field, which i want to assign in assignment shape:
As you can see, intellisense is suggesting me to select a node with my distinguished field. But when i select it, i get an error!
I've faced this before, and restarting VS always helped. But not this time :(
Message is a reserved word in XLang. Can you change the name of the element/attribute that backs this distinguished field to something else? If that does not work, you could always XPath to the element to read it and use it. Last if those two don't work, you could make this a promoted property where you are able to specify the name yourself.
Here is the list of reserved words.
http://msdn.microsoft.com/en-us/library/aa547020.aspx
I have a lot of objects with unique IDs. Every object can have several labels associated to it, like this:
123: ['a', 'hello']
456: ['dsajdaskldjs']
789: (no labels associated yet)
I'm not planning to store all objects in DynamoDB, only these sets of labels. So it would make sense to add labels like that:
find a record with (id = needed_id)
if there is one, and it has a set named label_set, add a label to this set
if there is no record with such id, or the existing record doesn't have an attribute named label_set, create a record and an attribute, and initialize the attribute with a set consisting of the label
if I used sets of numbers, I could use just ADD operation of UPDATE command. This command does exactly what I described. However, this does not work with sets of strings:
If no item matches the specified primary key:
ADD— Creates an item with supplied primary key and number (or set of numbers) for the attribute value. Not valid for a string type.
so I have to use a PUT operation with Expected set to {"label_set":{"Exists":false}}, followed (in case it fails) by an ADD operation. These are two operations, and it kinda sucks (since you pay per operation, the costs of this will be 2 times more than they could be).
This limitations seems really weird to me. Why are something what works with numbers sets would not work with string sets? Maybe I'm doing something wrong.
Using many records like (123, 'a'), (123, 'hello') instead of one record per object with a set is not a solutions: I want to get all the values from the set at once, without any scans.
I use string sets from the Java SDK the way you describe all the time and it works for me. Perhaps it has changed? I basically follow the pattern in this doc:
http://docs.amazonwebservices.com/amazondynamodb/latest/developerguide/API_UpdateItem.html
ADD— Only use the add action for numbers or if the target attribute is
a set (including string sets). ADD does not work if the target
attribute is a single string value or a scalar binary value. The
specified value is added to a numeric value (incrementing or
decrementing the existing numeric value) or added as an additional
value in a string set. If a set of values is specified, the values are
added to the existing set. For example if the original set is [1,2]
and supplied value is [3], then after the add operation the set is
[1,2,3], not [4,5]. An error occurs if an Add action is specified for
a set attribute and the attribute type specified does not match the
existing set type.
If you use ADD for an attribute that does not exist, the attribute and
its values are added to the item.
When your set is empty, it means the attribute isn't present. You can still ADD to it. In fact, a pattern that I've found useful is to simply ADD without even checking for the item. If it doesn't exist, it will create a new item using the specified key and create the attribute set with the value(s) I am adding. If the item exists but the attribute doesn't, it creates the attribute set and adds the value(s). If they both exist, it just adds the value(s).
The only piece that caught me up at first was that the value I had to add was a SS (String set) even if it was only one string value. From DynamoDB's perspective, you are always merging sets, even if the existing set is an empty set (missing) or the new set only contains one value.
IMO, from the way you've described your intent, you would be better off not specifying an existing condition at all. You are having to do two steps because you are enforcing two different situations but you are trying to perform the same action in both. So might as well just blindly add the label and let DynamoDB handle the rest.
Maybe you could: (pseudo code)
try:
add_with_update_item(hash_key=42, "label")
except:
element = new Element(hash_key=42, labels=["label"])
element.save()
With this graceful recovery approach, you need 1 call in the general case, 2 otherwise.
You are unable to use sets to do what you want because Dynamo Db doesn't support empty sets. I would suggest just using a string with a custom schema and building the set from that yourself.
To avoid two operations, you can add a "ConditionExpression" to your item.
For example, add this field/value to your item:
"ConditionExpression": "attribute_not_exists(RecordID) and attribute_not_exists(label_set)"
Source documentation.
Edit: I found a really good guide about how to use the conditional statements
How can I determine the primitive Type of the bound column to a DataGrid control, when the control is created using AutoGeneratingColumn?
I have looked in all these classes: DataGridColumn, DataGridBoundColumn, DataGridTextColumn, and DataGridBoundColumn.Binding.
I am unable to determine which Type (primitive type) the columns are bound to. (They are Bound to a SQL table.) I want to apply different styles and converters based on the type. I could Hard Code these styles and converters based on the column name (which I can get from DataGridTextColumn.Header), but I want to AVOID THAT AT ALL COSTS!
Looks like I found the answer.
The type is passed into the "AutoGeneratingColumn" handler as e.PropertyType.
The problem is, it isn't the real type. It must be boxed, because even though the database column is "nullable" the type passed isn't.
So, I am going to have to "Hard Code" my solution, based on Column Name. :(