To solve various problems and to draw some conclusions we often have information already stored in our brain that we can utilize but how is that information stored in our brain there are a lot of possibilities today we are focusing on one of them which is the semantic semantic Network we will see how what is the meaning of semantic network.
The word semantics means meaning as a computer science student you are already familiar with two words syntax which is essentially the grammar of a language and semantics is the meaning of any sentence.
So I may form the sentence correctly which means it may be syntactically correct but it must be meaningful to be meaningful it should be semantically correct.
When do you say a particular sentence or statement is meaningful?
Sentence is meaningful when we can understand it and map it to some of the known concepts of the real world in which we live or see or can visualize or realize.
The association of the different concepts builds up our knowledge system, our conception, and our knowledge base. E.g. Chaiir in a room.
Represent knowledge as a network of different concepts
Knowledge Representation using Semantic Network
If we consider the Semantic net as a knowledge representation method or scheme then it must also have some particular inference mechanism by which it can utilize this representation to infer things to answer different questions.
Semantic Networks
A semantic network is a simple representation scheme that chooses a directed graph consisting of nodes that represent concepts and directed arcs that represent a segment between the concepts. Representing these concepts involves hierarchies of interconnected concept nodes.
For example, it is natural to draw the link between cats and animals to say that cats are animals. At a given level, a concept may possess multiple associative attributes. For instance, while an animal can walk and be heard, cats exhibit additional associations, such as liking mates, which are unique to them within the graph.
Node and Arcs
Nodes in the semantic network represent objects that may object to my name attribute or any attribute value and the arcs are links that define binary relations that hold between objects denoted by the nodes.
On the right side on the right, there is a propositional logic in front which is the equivalent semantic nets where the nodes represent the objects and where links are the predicates that are in the propositional logic.
Meaning of the Semantic Network
Knowledge Representation using Semantic Network
The structure of the network defines its meaning the meanings are merely which help which node has appointed to which other node the network defines a set of binary relations on a set of nodes.
Meaning of Semantic Networks
- The structure of the network defines its meaning.
- Which node has a pointer to which other node
Components of a Semantic Network
Semantic network representation consists of 4 parts:
Lexical: Which symbols are allowed in the representation’s vocabulary
Structural: Describes constraints on how the symbols can be arranged
Procedural: Specifies the access procedure (to create modify, and answer questions)
Semantic: Establishes the way of associating the meaning
- Nodes: The basic elements of a semantic network, representing concepts or entities. It denotes objects.
- Links/Edges: Connections between nodes representing relationships between concepts. Links denote relations.
- Labels: Labels denote particular objects and relations.
- Attributes: Properties or characteristics associated with nodes in the semantic network.
- Inheritance: Inheritance is one of the main kinds of reasoning done in semantic nets.
- Taxonomy: Hierarchical organization of concepts within the semantic network.
ISA relationship: The ISA relation is often used to link a class and its superclass. Some links (e.g. hasPart) are inherited along ISA paths.
Non-Binary Relations
We can represent the generic give event as a relation involving three things:
- A giver
- A recipient
- An object
“John gave Mary the book”
A semantic network is an alternative to predicate the logic.
gave( Jhon, Book1, Mary)
Conceptual Graphs
Conceptual graphs are semantic nets representing the meaning of (simple) sentences in natural language.
WordNet
An example of a semantic network is WordNet. A lexical database of English. It groups English words into sets of synonyms called synsets, provides short, general definitions, and records the various semantic relations between these synonym sets.
