Efficient Execution of Service Composition for Content Adaptation in Pervasive Computing

Algorithm 1

The MAGG algorithm structure.

Algorithm: graph (𝑆_𝐴,𝑆_𝑍,𝑇,𝐷)

Input: Initial state 𝑆_𝐴, final state 𝑆_𝑍, adaptation task list 𝑇 and adaptation operators 𝐷

Output: an adaptation graph 𝐺(𝑉,𝐸)

// Global constant

// Limit   maximum number of neutral operators allowed in a connection

// Global variables

// 𝑉 a set of nodes in a graph

// 𝐸 a set of edges in a graph

// 𝑎𝑜 start node

// 𝑧𝑜 end node

// 𝑁𝑂 a set of neutral operators available in the system

// Local variables

// 𝑇 a set of adaptation tasks

// 𝑡 an adaptation task element of 𝑇

// 𝑂 a set of nodes for adaptation operators realizing an adaptation task

// 𝑃𝑂 a set of parent nodes

// 𝑃_𝑧 a set containing the end node

Var

𝑉,𝐸,𝑇,𝑡,𝑂,𝑃𝑂,𝑎𝑜,𝑧𝑜,𝑃𝑧,𝑁𝑂

Begin

𝑎𝑜 = ConstructStartNode(𝑆_𝐴) // constructs the start node from the initial state

𝑧𝑜 = ConstructEndNode(𝑆_𝑍) // constructs the end node from the goal state

𝑁𝑂 = ConstructNeutralOperators() // returns the list of the neutral operators available in // the system

𝑉={𝑎𝑜} // initialization

𝐸=∅ // initialization

𝑃𝑂={𝑎𝑜} // initialization

for each 𝑡∈𝑇

Begin

Construct nodes 𝑂 from 𝐷 with operators realizing 𝑡

// several operators can realize a task

Connect (𝑂,𝑃𝑂)

// after the process 𝑃𝑂 holds the value of 𝑂

End // 𝑇 is processed

𝑃𝑧={𝑧𝑜}

Connect (𝑃𝑧,𝑃𝑂) // connects the end node

Return 𝐺(𝑉,𝐸)

End // graph