Fig 5 - uploaded by Yannis Stavrakas
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Snapshot reduction for T=5 of the evo-graph in Fig. 4
Source publication
In this paper we argue that changes should be treated as first class citizens in data management systems. In our approach, changes are not just transformation operations but complex objects retaining structural, semantic, and temporal characteristics. We believe that accommodating structured changes in information modeling and querying can provide...
Contexts in source publication
Context 1
... tree snapshot for the time instance T=5 of the evo- graph in Fig. 4 is shown in Fig. 5. Since the resulting tree does not contain any change nodes or evolution edges, it can be easily transformed to XML format, following a non replicated top-down traversal ...
Context 2
... of a data element (temporal queries): While browsing the current snapshot of the databank (Fig. 5) a bio- scientist named Brian realizes that the length of the miRNA with ID 'm2' is not what he expected, and engages in finding out what has happened and why. He starts by retrieving the previous versions of the data node &14 (see Fig. ...
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Citations
... We argue that in systems where evolution issues are paramount, changes should not be treated solely as transformation operations on the data, but rather as first class citizens retaining structural, semantic, and temporal characteristics. In previous work, we proposed a graph model, evo-graph [16], and its XML representation, evoXML [17], capturing the relationship between evolving data and changes applied on them. A key characteristic is that it explicitly models changes as first class citizens and thus, enables querying data and changes in a uniform way. ...
... The reduction of the evo-graph for T=start results in the snap-graph of the leftmost image of EvoXML. In [17] we have shown how evo-graph can be represented in an XML format, called evoXML. TABLE I. presents an evoXML example. ...
... Querying Evolution. Finally, in [16], [17] we have outlined evo-path, an XPath extension that help us posing regular queries over data snapshots as well as time-and change-aware queries on evo-graph. We have also shown how evo-path expressions can be evaluated on evoXML via equivalent XQuery expressions. ...
Evo-graph is a model for data evolution that encompasses multiple versions of data and treats changes as first-class citizens. A change in evo-graph can be compound, comprising disparate changes, and is associated with the data items it affects. In previous papers, we have shown that recording data evolution with evo-graph is very useful in cases where the provenance of the data needs to be traced, and past states of data need to be re-assessed. We have specified how an evo-graph can be reduced to the snapshot holding under a specified time instance, we have given an XML representation of evo-graph called evoXML, and we have presented how interesting queries can be answered. In this paper, we explain how evo-graph is used to record the history of data and the structure of changes step by step, as the current snapshot evolves. We present C2D, a novel framework that implements the concepts in the paper using XML technologies. Finally, we experimentally evaluate C2D for space and time efficiency and discuss the results.
