vault backup: 2023-10-16 12:13:34

4a1s/MFES/PL - Aula 4.md

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+16 Outubro 2023 - #MFES 
+
+
+## Alloy4Fun
+
+```c
+sig User {
+	follows : set User,
+	sees : set Photo,
+	posts : set Photo,
+	suggested : set User
+}
+
+sig Influencer extends User {}
+
+sig Photo {
+	date : one Day
+}
+sig Ad extends Photo {}
+
+sig Day {}
+// Specify the following properties.
+// You can check their correctness with the different commands and
+// when specifying each property you can assume all the previous ones to be true.
+
+pred inv1 {
+	// Every image is posted by one user.
+	all y: Photo | some x: User | x->y in posts
+	all x,y : User, z: Photo | x->z in posta 
+}
+ 
+
+pred inv2 {
+	// Users cannot follow themselves.
+
+}
+
+
+pred inv3 {
+	// Users can see ads posted by everyone, 
+	// but only see non ads posted by followed users.
+
+}
+
+
+pred inv4 {
+	// If a user posts an ad then all its posts should be labeled as ads. 
+
+}
+
+
+pred inv5 {
+	// Influencers are followed by everyone else.
+
+}
+
+
+pred inv6 {
+	// Influencers post every day.
+
+}
+
+
+pred inv7 {
+	// Suggested are other users followed by followed users, but not yet followed.
+	
+}
+
+
+pred inv8 {
+	// A user only sees ads from followed or suggested users.
+
+}
+
+```