16. RDF support¶
RDF (Resource Descriptor Framework) is a W3C recommendation for describing meta-content based on XML.
The basic data structure of RDF is a set of 3 pieces of data called “triple”, each of which consists of a subject (subject), a predicate (predicate), and an object (object).
For more information, see RDF Concepts And Abstract .
The related AIML tags are addtriple, deletetriple, select, tuple, uniq.
16.1. AIML triple file¶
“triple” is a single line of text with the subject, predicate and object separated by a colon ‘:’. In this program, this line is referred to as an element.
Explain the RDF definition with an airplane example.
In this definition, “subject” is listed as “AIRPLANE” and a number of “predicate” describe each value (“object”).
AIRPLANE:hasPurpose:to transport us through the air
AIRPLANE:hasSize:9
AIRPLANE:hasSpeed:12
AIRPLANE:hasSyllables:1
AIRPLANE:isa:Aircraft
AIRPLANE:isa:Transportation
AIRPLANE:lifeArea:Physical
16.2. AIML RDF Tag¶
AIML defines creation, deletion, and search tags such as “addtriple”, “deletetriple”, “select”, and “uniq”.
You can also use tags like “set”, “get”, “first”, and “rest” to process search results.
16.2.1. Load Element¶
This program has a function to load pre-prepared files.
Reads the RDF definition file under the conditions set in rdf_storage of config.
client_type:
storage:
entities:
rdf: file
stores:
file:
type: file
config:
rdf_storage:
dirs: ../storage/rdfs
subdirs: true
extension: txt
This section uses a definition file that describes the following.
ant:legs:6
ant:sound:scratch
bat:legs:2
bat:sound:eee
bear:legs:4
bear:sound:grrrrr
buffalo:legs:4
buffalo:sound:moo
cat:legs:4
cat:sound:meow
chicken:legs:2
chicken:sound:cluck cluck
dolphin:legs:0
dolphin:sound:meep meep
fish:legs:0
fish:sound:bubble bubble
16.2.2. Element Generation¶
A new “triple” can be dynamically added using not only loading data but also the addtriple element.
<addtriple>
<subj>Subject</subj><pred>Predicate</pred><obj>Object</obj>
</addtriple>
An example of adding animal characteristics.
<addtriple>
<subj>cow</subj><pred>sound</pred><obj>moo</obj>
</addtriple>
<addtriple>
<subj>dog</subj><pred>sound</pred><obj>woof</obj>
</addtriple>
However, data added with addtriple is not persisted.
16.2.3. Delete Element¶
Any data including data added by the addtriple element or read from the file can be deleted using the deletetriple element. This includes not only elements added by addtriple, but also elements read from the file.
<deletetriple>
<subj>cow</subj><pred>sound</pred><obj>moo</obj>
</deletetriple>
<deletetriple>
<subj>ant</subj><pred>sound</pred><obj>scratch</obj>
</deletetriple>
If you specify three elements (subject, predicate, and object), only the elements that match all of them will be deleted.
If only subject and predicate are specified, matching elements are removed, regardless of the value of object.
If only subject is specified, all elements matching that subject are removed.
16.2.4. Search¶
The select element is used to search RDF.
16.2.4.1. Simple Search¶
In the case of a simple search, if you specify subject, predicate, and object as the contents of the <q> element, the contents registered as matching results will be returned as a list.
<select>
<q><subj>dog</subj><pred>sound</pred><obj>woof</obj></q>
</select>
If that information exists, the following results are returned.
[[[[“subj”, “DOG”], [“pred”, “SOUND”], [“obj”, “woof”]]]]
If you want to retrieve only one specific element, the following can be described.
<select>
<q><subj>dog</subj><pred>sound</pred><obj>?</obj></q>
</select>
In this case, the following result indicating the contents of the element specified with “?” Is returned.
[[[“?”, “woof”]]]
16.2.4.2. Searching by Variable¶
If you want to return multiple elements or receive a list of matching elements, you must use variables.
Variables are defined in the contents of the vars tag and are prefixed with the variable name “?”.
The query <q> allows you to set a variable in the tag of an element of triple.
In the following case, variable:?x is subject, variable:?y is predicate, variable:?z is the object to store.
<select>
<vars>?x ?y ?z</vars>
<q><subj>?x</subj><pred>?y</pred><obj>?z</obj></q>
</select>
You can get the data corresponding to the variable from all the triples that match the specified data.
The following example searches for the number of feet (legs) in an animal.
<select>
<vars>?x ?y</vars>
<q><subj>?x</subj><pred>legs</pred><obj>?y</obj></q>
</select>
If the search results match, you will get the following results.
[[[“?x”, “ANT”], [“?y”, “6”]], [[“?x”, “BAT”], [“?y”, “2”]], [[“?x”, “BEAR”], [“?y”, “4”]], [[“?x”, “BUFFALO”], [“?y”, “4”]], [[“?x”, “CAT”], [“?y”, “4”]], [[“?x”, “CHICKEN”], [“?y”, “2”]], [[“?x”, “DOLPHIN”], [“?y”, “0”]], [[“?x”, “FISH”], [“?y”, “0”]]]
16.2.4.3. Complex Condition Search¶
If you need to perform more complex searches, you can chain multiple queries, each joined as a ‘and’ query.
There are 2 types of queries. <q> tag returns results matching its condition and <notq> tag returns results not matching its condition.
<select>
<vars>?x ?y ?z</vars>
<q><subj>?x</subj><pred>legs</pred><obj>?y</obj></q>
<notq><subj>?z</subj><pred>legs</pred><obj>0</obj></notq>
</select>
16.2.4.4. Data Retrieval¶
The select element is used to create a data set, as in the SQL SELECT statement.
The following example stores the result of a select element in tuples using the ‘set’ tag.
<set var="tuples">
<select>
<vars>?x ?y</vars>
<q><subj>?x</subj><pred>sound</pred><obj>?y</obj></q>
</select>
</set>
In this case, the following contents are set in tuples.
[[[“?x”, “BAT”], [“?y”, “eee”]], [[“?x”, “BEAR”], [“?y”, “grrrrr”]], [[“?x”, “BUFFALO”], [“?y”, “moo”]], [[“?x”, “CAT”], [“?y”, “meow”]], [[“?x”, “CHICKEN”], [“?y”, “cluck cluck”]], [[“?x”, “DOLPHIN”], [“?y”, “meep meep”]], [[“?x”, “FISH”], [“?y”, “bubble bubble”]], [[“?x”, “DOG”], [“?y”, “woof”]]]
To get the data generated from the ‘select’ element described above, use the ‘tuple’ element to get the ‘get’ tag as a child element.
<get var="?x">
<tuple>
<get var="tuples" />
</tuple>
</get>
<get var="?y">
<tuple>
<get var="tuples" />
</tuple>
</get>
In this example, the ‘var’ attribute of get specifies the variable “?x” specified in the select element.
By specifying “tuples” (list object) that stores the result of the select element in the tuple tag, data corresponding to the variable “?x” can be obtained from “tuples”.
As a result, the following contents can be obtained from the variable “?x”.
BAT BEAR BUFFALO CAT CHICKEN DOLPHIN FISH DOG
Similarly, the following contents can be obtained from the variable “?y”.
eee grrrrr moo meow cluck cluck meep meep bubble bubble woof
Also, by using the first tag and rest tag for “tuples”, partial results can be obtained as follows.
<get var="?x">
<tuple>
<first><get var="tuples" /></first>
</tuple>
</get>
<get var="?y">
<tuple>
<rest><get var="tuples" /></rest>
</tuple>
</get>
As a result, in the first tag (obtaining first data), the value obtained from the variable “?x” is as follows.
BAT
Similarly, the value obtained from the variable “?y” with the rest tag (obtaining data other than the head) is as follows.
grrrrr moo meow cluck cluck meep meep bubble bubble woof