Enumerating XML Data for Dynamic Updating L.Kit and V.Ng, Hong Kong Polytechnique University Sang-Ho Nah Lily Daniel Yun Hee Lee

Introduction n-Inode: new model-mapping approach Multidimensional node ID for indexing and node-to-node relationship calculation Supports dynamic updating of XML data flexibly

n-INode XML document represented as n c -ary complete tree, where n c =maximum number of child node per node Multidimensional node ID: k-dimensional ID:(id 1, io 1, id 2, io 2, …, id k, io k ) id x : Node identifier assigned by numbering scheme io x : Insertion order, sequential number starting from 0 Presence of io x allows more than n c child nodes to be inserted. No re-calculation of existing nodes’ id required

n-INode cont Insertion Rules  If newly inserted node’s id 1 exists in the tree, its io 1 is incremented from maximum io 1 among existing nodes with the same id 1  If new node is inserted to the “right most position”, and maximum io 1 (of all the nodes with the same id 1 ) is less than n c, then io 1 = n c +1  A new dimension is introduced to all descendants of a node that has io 1 > 0. Parent’s first dimension is assigned to the child’s first dimension.

n-INode cont Parent-Child relationship:  Pair of nodes with the same number of dimensions  Pair of nodes with dimensional difference of one  Parent and Child MUST share the identical first dimension Ancestor-Descendant relationship:  Above 2 situations  Pair of nodes with dimensional difference of more than one

Implementation & Experiment Required storage space is not the smallest of all the models tested Other test results show that this is a reasonable trade-off Query time is reasonable and consistent – shows it does not depend heavily on the type of query

Possible flaws in n-INode Node relationship calculation/verification rule excludes a case where both nodes in the pair have 1-dimensional ID (first dimensions cannot be the same) Path sequence of each node changes by allowing more than n c child nodes to be inserted – therefore path sequence should not be used in node identifier calculation

Conclusion Identifying the insertion order removes restriction on the number of child nodes to be inserted Re-calculation of existing nodes’ ID is not required This allows for more effective and efficient node locating operation, supporting dynamic updates of XML data. However, some aspects were overlooked and this makes the proof of correctness presented in the paper somewhat deficient.