We define a construction operation on hypergraphs using a colimit and show that its expressiveness concerning graph rewriting is equal to the graph expressions of Courcelle and the double-pushout approach of Ehrig. With an inductive way of representing graphs, graph rewriting arises naturally as a derived concept. The usefulness of our approach for the compositional modelling of concurrent syst...

The edit operation that contracts edges, which is a fundamental operation in the theory of graph minors, has recently gained substantial scientific attention from the viewpoint of Parameterized Complexity. In this paper, we examine an important family of graphs, namely the family of split graphs, which in the context of edge contractions, is proven to be significantly less obedient than one mig...

The link of a vertex v in a graph G is the subgraph induced by all vertices adjacent to v. If all the links in G are isomorphic to the same graph L, then L is called the link graph of G. We consider the operation of an amalgamation of graphs. Using the construction of the free product of groups with amalgamated subgroups, we give a sufficient condition for a class of link graphs of Cayley graph...

We propose broadcasting algorithms for line digraphs in the telephone model. The new protocols use a broadcasting protocol for a graph G to obtain a broadcasting protocol for the graph L k (G), the graph obtained by applying k times, the line digraph operation to G. As a consequence improved bounds for the broadcasting time in De Bruijn, Kautz and Wrapped Butterry digraphs are obtained.

We analyzed three functions of Twitter (Favorite, Follow and Mention) from network structural point of view. These three functions are characterized by difference and similarity in various measures defined in directed graphs. Favorite function can be viewed by three different graph representations: a simple graph, a multigraph and a bipartite graph, Follow function by one graph representation: ...

Let Γ = (G,σ) be a signed graph, where σ is the sign function on edges of G. In this paper, we use operation partial transpose to obtain non-isomorphic Laplacian cospectral graphs. We will introduce two new operations These establish relationship between adjacency spectrum one graph with another graph. As an application, these utilized construct several pairs Finally, integral

This paper describes a new concept for the parallel implementation of functional languages on a network of processors. The implementation uses a special variant of annotated graph reduction 3]. The main features of it are the following: We employ active waiting 6], to avoid complicated runtime data structures. We use a global address space, and a random distribution of the graph nodes over the ...

For a graph Γ with adjacency matrix A, we consider a switching operation that takes Γ into a graph Γ′ with adjacency matrix A′, defined by A′ = Q > AQ, where Q is a regular orthogonal matrix of level 2 (that is, Q > Q = I, Q1 = 1, 2Q is integral, and Q is not a permutation matrix). If such an operation exists, and Γ is nonisomorphic with Γ′, then we say that Γ′ is semi-isomorphic with Γ. Semiis...

We describe an operation to dynamically adapt the structure of the Tanner graph used during iterative decoding. Codes on graphs– most importantly, low-density parity-check (LDPC) codes–exploit randomness in the structure of the code. Our approach is to introduce a similar degree of controlled randomness into the operation of the messagepassing decoder, to improve the performance of iterative de...

A dynamic algorithm was characterized by the concept of an “on-line” sequence of operations on a data structure. These operations being query and update. Each operation may be performed before the next operation is known. For example, if you had a directed graph, an intermixing of updates and queries to this graph can be made. A query might be: is there a directed path between two nodes of the ...