# the_great_game/gossip/news_items.clj

001 (ns the-great-game.gossip.news-items
002 "Categories of news events interesting to gossip agents"
003 (:require [the-great-game.world.location :refer [distance-between]]
004 [the-great-game.time :refer [game-time]]))
005
006 ;; The ideas here are based on the essay 'The spread of knowledge in a large
007 ;; game world', q.v.; they've advanced a little beyond that and will doubtless
008 ;; advance further in the course of writing and debugging this namespace.
009
010 ;; A news item is a map with the keys:
011 ;;
012 ;; * `date` - the date on which the reported event happened;
013 ;; * `nth-hand` - the number of agents the news item has passed through;
014 ;; * `verb` - what it is that happened (key into `news-topics`);
015 ;;
016 ;; plus other keys taken from the `keys` value associated with the verb in
017 ;; `news-topics`
018
019 (def news-topics
020 "Topics of interest to gossip agents. Topics are keyed in this map by
021 their `verbs`. The `keys` associated with each topic are the extra pieces
022 of information required to give context to a gossip item. Generally:
023
024 * `actor` is the id of the character who it is reported performed the
025 action;
026 * `other` is the id of the character on whom it is reported the action
027 was performed;
028 * `location` is the place at which the action was performed;
029 * `object` is an object (or possibly list of objects?) relevant to the
030 action;
031 * `price` is special to buy/sell, but of significant interest to merchants.
032
033 #### Notes:
034
035 ##### Characters:
036
037 *TODO* but note that at most all the receiver can learn about a character
038 from a news item is what the giver knows about that character, degraded by
039 what the receiver finds interesting about them. If we just pass the id here,
040 then either the receiver knows everything in the database about the
041 character, or else the receiver knows nothing at all about the character.
042 Neither is desirable. Further thought needed.
043
044 By implication, the character values passed should include *all* the
045 information the giver knows about the character; that can then be degraded
046 as the receiver stores only that segment which the receiver finds
047 interesting.
048
049 ##### Locations:
050
051 A 'location' value is a list comprising at most the x/y coordinate location
052 and the ids of the settlement and region (possibly hierarchically) that contain
053 the location. If the x/y is not local to the home of the receiving agent, they
054 won't remember it and won't pass it on; if any of the ids are not interesting
055 So location information will degrade progressively as the item is passed along.
056
057 It is assumed that the `:home` of a character is a location in this sense.
058
059 ##### Inferences:
060
061 If an agent learns that Adam has married Betty, they can infer that Betty has
062 married Adam; if they learn that Charles killed Dorothy, that Dorothy has died.
063 I'm not convinced that my representation of inferences here is ideal.
064 "
065 { ;; A significant attack is interesting whether or not it leads to deaths
066 :attack {:verb :attack :keys [:actor :other :location]}
067 ;; Deaths of characters may be interesting
068 :die {:verb :die :keys [:actor :location]}
069 ;; Deliberate killings are interesting.
070 :kill {:verb :kill :keys [:actor :other :location]
071 :inferences [{:verb :die :actor :other :other :nil}]}
072 ;; Marriages may be interesting
073 :marry {:verb :marry :keys [:actor :other :location]
074 :inferences [{:verb :marry :actor :other :other :actor}]}
075 ;; The end of ongoing open conflict between to characters may be interesting
076 :peace {:verb :peace :keys [:actor :other :location]
077 :inferences [{:verb :peace :actor :other :other :actor}]}
078 ;; Things related to the plot are interesting, but will require special
079 ;; handling. Extra keys may be required by particular plot events.
080 :plot {:verb :plot :keys [:actor :other :object :location]}
081 ;; Rapes are interesting.
082 :rape {:verb :rape :keys [:actor :other :location]
083 ;; Should you also infer from rape that actor is male and adult?
084 :inferences [{:verb :attack}
085 {:verb :sex}
086 {:verb :sex :actor :other :other :actor}]}
087 ;; Merchants, especially, are interested in prices in other markets
088 :sell {:verb :sell :keys [:actor :other :object :location :price]}
089 ;; Sex can juicy gossip, although not normally if the participants are in an
090 ;; established sexual relationship.
091 :sex {:verb :sex :keys [:actor :other :location]
092 :inferences [{:verb :sex :actor :other :other :actor}]}
093 ;; Thefts are interesting
094 :steal {:verb :steal :keys [:actor :other :object :location]}
095 ;; The succession of rulers is interesting; of respected craftsmen,
096 ;; potentially also interesting.
097 :succession {:verb :succession :keys [:actor :other :location :rank]}
098 ;; The start of ongoing open conflict between to characters may be interesting
099 :war {:verb :war :keys [:actor :other :location]
100 :inferences [{:verb :war :actor :other :other :actor}]}
101 })
102
103
104 (defn interest-in-character
105 "Integer representation of how interesting this `character` is to this
106 `gossip`.
107 *TODO:* this assumes that characters are passed as keywords, but, as
108 documented above, they probably have to be maps, to allow for degradation."
109 [gossip character]
110 (count
111 (concat
112 (filter #(= (:actor % character)) (:knowledge gossip))
113 (filter #(= (:other % character)) (:knowledge gossip)))))
114
115 (defn interesting-character?
116 "Boolean representation of whether this `character` is interesting to this
117 `gossip`."
118 [gossip character]
119 (> (interest-in-character gossip character) 0))
120
121 (defn interest-in-location
122 "Integer representation of how interesting this `location` is to this
123 `gossip`."
124 [gossip location]
125 (cond
126 (and (map? location) (number? (:x location)) (number? (:y location)))
127 (if-let [home (:home gossip)]
128 (let [d (distance-between location home)
129 i (/ 10000 d) ;; 10000 at metre scale is 10km; interest should
130 ;;fall off with distance from home, but possibly on a log scale
131 ]
132 (if (> i 1) i 0))
133 0)
134 (coll? location)
135 (reduce
136 +
137 (map
138 #(interest-in-location gossip %)
139 location))
140 :else
141 (count
142 (filter
143 #(some (fn [x] (= x location)) (:location %))
144 (cons {:location (:home gossip)} (:knowledge gossip))))))
145
146 ;; (interest-in-location {:home [{0, 0} :test-home] :knowledge []} [:test-home])
147
148 (defn interesting-location?
149 "True if the location of this news `item` is interesting to this `gossip`."
150 [gossip item]
151 (> (interest-in-location gossip (:location item)) 0))
152
153 (defn interesting-object?
154 [gossip object]
155 ;; TODO: Not yet (really) implemented
156 true)
157
158 (defn interesting-topic?
159 [gossip topic]
160 ;; TODO: Not yet (really) implemented
161 true)
162
163 (defn interesting-item?
164 "True if anything about this news `item` is interesting to this `gossip`."
165 [gossip item]
166 (or
167 (interesting-character? gossip (:actor item))
168 (interesting-character? gossip (:other item))
169 (interesting-location? gossip (:location item))
170 (interesting-object? gossip (:object item))
171 (interesting-topic? gossip (:verb item))))
172
173 (defn infer
174 "Infer a new knowledge item from this `item`, following this `rule`"
175 [item rule]
176 (reduce merge
177 item
178 (cons
179 {:verb (:verb rule)}
180 (map (fn [k] {k (apply (k rule) (list item))})
181 (remove
182 #(= % :verb)
183 (keys rule))))))
184
185 (declare learn-news-item)
186
187 (defn make-all-inferences
188 "Return a list of knowledge entries that can be inferred from this news
189 `item`."
190 [item]
191 (set
192 (reduce
193 concat
194 (map
195 #(:knowledge (learn-news-item {} (infer item %) false))
196 (:inferences (news-topics (:verb item)))))))
197
198 (defn degrade-character
199 "Return a character specification like this `character`, but comprising
200 only those properties this `gossip` is interested in."
201 [gossip character]
202 ;; TODO: Not yet (really) implemented
203 character)
204
205 (defn degrade-location
206 "Return a location specification like this `location`, but comprising
207 only those elements this `gossip` is interested in. If none, return
208 `nil`."
209 [gossip location]
210 (let [l (if
211 (coll? location)
212 (filter
213 #(when (interesting-location? gossip %) %)
214 location))]
215 (when-not (empty? l) l)))
216
217 (defn learn-news-item
218 "Return a gossip like this `gossip`, which has learned this news `item` if
219 it is of interest to them."
220 ;; TODO: Not yet implemented
221 ([gossip item]
222 (learn-news-item gossip item true))
223 ([gossip item follow-inferences?]
224 (if
225 (interesting-item? gossip item)
226 (let
227 [g (assoc
228 gossip
229 :knowledge
230 (cons
231 (assoc
232 item
233 :nth-hand (if
234 (number? (:nth-hand item))
235 (inc (:nth-hand item))
236 1)
237 :time-stamp (if
238 (number? (:time-stamp item))
239 (:time-stamp item)
240 (game-time))
241 :location (degrade-location gossip (:location item))
242 ;; TODO: ought to maybe-degrade characters we're not yet interested in
243 )
244 ;; TODO: ought not to add knowledge items we already have, except
245 ;; to replace if new item is of increased specificity
246 (:knowledge gossip)))]
247 (if follow-inferences?
248 (assoc
249 g
250 :knowledge
251 (concat (:knowledge g) (make-all-inferences item)))
252 g))
253 gossip)))
254
255
256