摘要
While the schema-less feature of the OEM (Object Exchange Model) gives fiexibility in representing semi-structured data, it brings difficulty in formulating database queries.Extracting schema from an OEM database then becomes an important research topic.This paper presents a new approach to this topic with the following features. (1) In addition to representing the nested label structure of an OEM database, the proposed OEM schema keeps upto-date information about instance objects of the database.The object-level information is useful in speeding up query evaluation. (2) The OEM schema is explicitly represented as a label-set, which is easy to construct and update.(3) The OEM schema of a database is statically built and dynamically updated. The time complexity of building the OEM schema is linear in the size of the OEM database.(4) The approach is applicable to a wide range of areas where the underlying schema is much smaller than the database itself (e.g. data warehouses that are made from a set of heterogeneous databases).
While the schema-less feature of the OEM (Object Exchange Model) gives fiexibility in representing semi-structured data, it brings difficulty in formulating database queries.Extracting schema from an OEM database then becomes an important research topic.This paper presents a new approach to this topic with the following features. (1) In addition to representing the nested label structure of an OEM database, the proposed OEM schema keeps upto-date information about instance objects of the database.The object-level information is useful in speeding up query evaluation. (2) The OEM schema is explicitly represented as a label-set, which is easy to construct and update.(3) The OEM schema of a database is statically built and dynamically updated. The time complexity of building the OEM schema is linear in the size of the OEM database.(4) The approach is applicable to a wide range of areas where the underlying schema is much smaller than the database itself (e.g. data warehouses that are made from a set of heterogeneous databases).
