The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform

Kamalakar Karlapalem - One of the best experts on this subject based on the ideXlab platform.

  • FODO - A mechanism of structural join index Hierarchy for efficient complex object retrieval
    Information Organization and Databases, 2000
    Co-Authors: Chi-wai Fung, Kamalakar Karlapalem
    Abstract:

    In this chapter, a novel indexing method --- structural join index Hierarchy --- is proposed to handle the complex object retrieval without using a sequence of expensive pointer chasing operations. The structural join index Hierarchy mimics the class Composition Hierarchy of the complex objects and provides direct access to them and their component objects. Structural join index Hierarchy extends the work on join index hierarchies by providing efficient and flexible access to complex objects. Moreover, this method unifies various previous indexing methods proposed for OODBs. We present performance evaluation to illustrate the utility of structural join index Hierarchy over other indexing methods for complex object retrieval.

  • star snow flake schema driven object relational data warehouse design and query processing strategies
    Data Warehousing and Knowledge Discovery, 1999
    Co-Authors: Vivekanand Gopalkrishnan, Kamalakar Karlapalem
    Abstract:

    The conventional star schema model of Data Warehouse (DW) has its limitations due to the nature of the relational data model. Firstly, this model cannot represent the semantics and operations of multi-dimensional data adequately. Due to the hidden semantics, it is difficult to efficiently address the problems of view design. Secondly, as we move up to higher levels of summary data (multiple complex aggregations), SQL queries do not portray the intuition needed to facilitate buildingand supporting efficient execution of complex queries on complex data. In light of these issues, we propose the Object-Relational View (ORV) design for DWs. Using Object-Oriented (O-O) methodology, we can explicitly represent the semantics and reuse view (class) definitions based on the ISA Hierarchy and the class Composition hierarchies, thereby resulting in a more efficient view mechanism. Part of the design involves providing a translation mechanism from the star/snowflake schema to an O-O representation. This is done by flattening the fact-dimension schema and converting it to a class-Composition Hierarchy in an O-O framework. Vertically partitioning this O-O schema further increases the efficiency of query execution by reducing disk access. We then build a Structural Join Index Hierarchy (SJIH) on this partitioned schema to facilitate complex object retrieval and avoid using a sequence of expensive pointer chasing (or join) operations.

  • DaWaK - Star/Snow-Flake Schema Driven Object-Relational Data Warehouse - Design and Query Processing Strategies
    DataWarehousing and Knowledge Discovery, 1999
    Co-Authors: Vivekanand Gopalkrishnan, Kamalakar Karlapalem
    Abstract:

    The conventional star schema model of Data Warehouse (DW) has its limitations due to the nature of the relational data model. Firstly, this model cannot represent the semantics and operations of multi-dimensional data adequately. Due to the hidden semantics, it is difficult to efficiently address the problems of view design. Secondly, as we move up to higher levels of summary data (multiple complex aggregations), SQL queries do not portray the intuition needed to facilitate buildingand supporting efficient execution of complex queries on complex data. In light of these issues, we propose the Object-Relational View (ORV) design for DWs. Using Object-Oriented (O-O) methodology, we can explicitly represent the semantics and reuse view (class) definitions based on the ISA Hierarchy and the class Composition hierarchies, thereby resulting in a more efficient view mechanism. Part of the design involves providing a translation mechanism from the star/snowflake schema to an O-O representation. This is done by flattening the fact-dimension schema and converting it to a class-Composition Hierarchy in an O-O framework. Vertically partitioning this O-O schema further increases the efficiency of query execution by reducing disk access. We then build a Structural Join Index Hierarchy (SJIH) on this partitioned schema to facilitate complex object retrieval and avoid using a sequence of expensive pointer chasing (or join) operations.

Vivekanand Gopalkrishnan - One of the best experts on this subject based on the ideXlab platform.

  • star snow flake schema driven object relational data warehouse design and query processing strategies
    Data Warehousing and Knowledge Discovery, 1999
    Co-Authors: Vivekanand Gopalkrishnan, Kamalakar Karlapalem
    Abstract:

    The conventional star schema model of Data Warehouse (DW) has its limitations due to the nature of the relational data model. Firstly, this model cannot represent the semantics and operations of multi-dimensional data adequately. Due to the hidden semantics, it is difficult to efficiently address the problems of view design. Secondly, as we move up to higher levels of summary data (multiple complex aggregations), SQL queries do not portray the intuition needed to facilitate buildingand supporting efficient execution of complex queries on complex data. In light of these issues, we propose the Object-Relational View (ORV) design for DWs. Using Object-Oriented (O-O) methodology, we can explicitly represent the semantics and reuse view (class) definitions based on the ISA Hierarchy and the class Composition hierarchies, thereby resulting in a more efficient view mechanism. Part of the design involves providing a translation mechanism from the star/snowflake schema to an O-O representation. This is done by flattening the fact-dimension schema and converting it to a class-Composition Hierarchy in an O-O framework. Vertically partitioning this O-O schema further increases the efficiency of query execution by reducing disk access. We then build a Structural Join Index Hierarchy (SJIH) on this partitioned schema to facilitate complex object retrieval and avoid using a sequence of expensive pointer chasing (or join) operations.

  • DaWaK - Star/Snow-Flake Schema Driven Object-Relational Data Warehouse - Design and Query Processing Strategies
    DataWarehousing and Knowledge Discovery, 1999
    Co-Authors: Vivekanand Gopalkrishnan, Kamalakar Karlapalem
    Abstract:

    The conventional star schema model of Data Warehouse (DW) has its limitations due to the nature of the relational data model. Firstly, this model cannot represent the semantics and operations of multi-dimensional data adequately. Due to the hidden semantics, it is difficult to efficiently address the problems of view design. Secondly, as we move up to higher levels of summary data (multiple complex aggregations), SQL queries do not portray the intuition needed to facilitate buildingand supporting efficient execution of complex queries on complex data. In light of these issues, we propose the Object-Relational View (ORV) design for DWs. Using Object-Oriented (O-O) methodology, we can explicitly represent the semantics and reuse view (class) definitions based on the ISA Hierarchy and the class Composition hierarchies, thereby resulting in a more efficient view mechanism. Part of the design involves providing a translation mechanism from the star/snowflake schema to an O-O representation. This is done by flattening the fact-dimension schema and converting it to a class-Composition Hierarchy in an O-O framework. Vertically partitioning this O-O schema further increases the efficiency of query execution by reducing disk access. We then build a Structural Join Index Hierarchy (SJIH) on this partitioned schema to facilitate complex object retrieval and avoid using a sequence of expensive pointer chasing (or join) operations.

Cedric Blanpain - One of the best experts on this subject based on the ideXlab platform.

  • defining the mode of tumour growth by clonal analysis
    Nature, 2012
    Co-Authors: Gregory Driessens, Benjamin Beck, Amelie Caauwe, Benjamin D Simons, Cedric Blanpain
    Abstract:

    Recent studies using the isolation of a subpopulation of tumour cells followed by their transplantation into immunodeficient mice provide evidence that certain tumours, including squamous skin tumours, contain cells with high clonogenic potential that have been referred to as cancer stem cells (CSCs). Until now, CSC properties have only been investigated by transplantation assays, and their existence in unperturbed tumour growth is unproven. Here we make use of clonal analysis of squamous skin tumours using genetic lineage tracing to unravel the mode of tumour growth in vivo in its native environment. To this end, we used a genetic labelling strategy that allows individual tumour cells to be marked and traced over time at different stages of tumour progression. Surprisingly, we found that the majority of labelled tumour cells in benign papilloma have only limited proliferative potential, whereas a fraction has the capacity to persist long term, giving rise to progeny that occupy a significant part of the tumour. As well as confirming the presence of two distinct proliferative cell compartments within the papilloma, mirroring the Composition, Hierarchy and fate behaviour of normal tissue, quantitative analysis of clonal fate data indicates that the more persistent population has stem-cell-like characteristics and cycles twice per day, whereas the second represents a slower cycling transient population that gives rise to terminally differentiated tumour cells. Such behaviour is shown to be consistent with double-labelling experiments and detailed clonal fate characteristics. By contrast, measurements of clone size and proliferative potential in invasive squamous cell carcinoma show a different pattern of behaviour, consistent with geometric expansion of a single CSC population with limited potential for terminal differentiation. This study presents the first experimental evidence for the existence of CSCs during unperturbed solid tumour growth.

  • Defining the mode of tumour growth by clonal analysis
    Nature, 2012
    Co-Authors: Gregory Driessens, Benjamin Beck, Amelie Caauwe, Benjamin D Simons, Cedric Blanpain
    Abstract:

    Using genetic lineage tracing, tumour cells are traced in vivo in an unperturbed solid tumour; in a carcinogen-induced papilloma mouse model, cells in these benign lesions are found to mirror the clonal Hierarchy organization of normal tissue. Recent studies using the isolation of a subpopulation of tumour cells followed by their transplantation into immunodeficient mice provide evidence that certain tumours^ 1 , 2 , including squamous skin tumours^ 3 , 4 , 5 , contain cells with high clonogenic potential that have been referred to as cancer stem cells (CSCs). Until now, CSC properties have only been investigated by transplantation assays, and their existence in unperturbed tumour growth is unproven. Here we make use of clonal analysis of squamous skin tumours using genetic lineage tracing to unravel the mode of tumour growth in vivo in its native environment. To this end, we used a genetic labelling strategy that allows individual tumour cells to be marked and traced over time at different stages of tumour progression. Surprisingly, we found that the majority of labelled tumour cells in benign papilloma have only limited proliferative potential, whereas a fraction has the capacity to persist long term, giving rise to progeny that occupy a significant part of the tumour. As well as confirming the presence of two distinct proliferative cell compartments within the papilloma, mirroring the Composition, Hierarchy and fate behaviour of normal tissue, quantitative analysis of clonal fate data indicates that the more persistent population has stem-cell-like characteristics and cycles twice per day, whereas the second represents a slower cycling transient population that gives rise to terminally differentiated tumour cells. Such behaviour is shown to be consistent with double-labelling experiments and detailed clonal fate characteristics. By contrast, measurements of clone size and proliferative potential in invasive squamous cell carcinoma show a different pattern of behaviour, consistent with geometric expansion of a single CSC population with limited potential for terminal differentiation. This study presents the first experimental evidence for the existence of CSCs during unperturbed solid tumour growth. Using genetic-lineage tracing, Cedric Blanpain and colleagues for the first time clonally trace tumour cells in vivo in an unperturbed solid tumour. In a carcinogen-induced papilloma mouse model, they find that the cells in these benign lesions mirror the clonal Hierarchy organization of normal tissue. Only a fraction of papilloma cells with a higher proliferative potential is able to sustain a second, slower-cycling transient population that gives rise to the differentiated tumour cells that form the bulk of the papillomas. But when lesions progress to squamous cell carcinomas, there is a switch to mainly self-renewing divisions and limited differentiation, suggesting that these cells may represent a cancer stem cell population. Evidence for cancer stem cells — a subset of tumour cells able to maintain tumour growth — has previously been demonstrated only in solid tumours in transplantation experiments.

Joseph Fong - One of the best experts on this subject based on the ideXlab platform.

  • Translating object-oriented database transactions into relational transactions
    Information and Software Technology, 2002
    Co-Authors: Joseph Fong
    Abstract:

    Abstract In this paper, we present methods of translating transactions from object-oriented database (OODB) to relational database (RDB). The process involves schema mapping in data definition language and transaction translation in data manipulation language. They include scheme definition, data query and transaction operation of insert, update, and deletion. We also discuss the object-oriented features in OODB operations that are not supported by RDB, such as class Hierarchy, class Composition Hierarchy, and set attribute, and provide a general solution to realize those mechanisms by traditional relation operations. The result of the transaction translation can be applied into adding object-oriented interface into relational database management system and to the interoperability between OODB and RDB.

Gregory Driessens - One of the best experts on this subject based on the ideXlab platform.

  • defining the mode of tumour growth by clonal analysis
    Nature, 2012
    Co-Authors: Gregory Driessens, Benjamin Beck, Amelie Caauwe, Benjamin D Simons, Cedric Blanpain
    Abstract:

    Recent studies using the isolation of a subpopulation of tumour cells followed by their transplantation into immunodeficient mice provide evidence that certain tumours, including squamous skin tumours, contain cells with high clonogenic potential that have been referred to as cancer stem cells (CSCs). Until now, CSC properties have only been investigated by transplantation assays, and their existence in unperturbed tumour growth is unproven. Here we make use of clonal analysis of squamous skin tumours using genetic lineage tracing to unravel the mode of tumour growth in vivo in its native environment. To this end, we used a genetic labelling strategy that allows individual tumour cells to be marked and traced over time at different stages of tumour progression. Surprisingly, we found that the majority of labelled tumour cells in benign papilloma have only limited proliferative potential, whereas a fraction has the capacity to persist long term, giving rise to progeny that occupy a significant part of the tumour. As well as confirming the presence of two distinct proliferative cell compartments within the papilloma, mirroring the Composition, Hierarchy and fate behaviour of normal tissue, quantitative analysis of clonal fate data indicates that the more persistent population has stem-cell-like characteristics and cycles twice per day, whereas the second represents a slower cycling transient population that gives rise to terminally differentiated tumour cells. Such behaviour is shown to be consistent with double-labelling experiments and detailed clonal fate characteristics. By contrast, measurements of clone size and proliferative potential in invasive squamous cell carcinoma show a different pattern of behaviour, consistent with geometric expansion of a single CSC population with limited potential for terminal differentiation. This study presents the first experimental evidence for the existence of CSCs during unperturbed solid tumour growth.

  • Defining the mode of tumour growth by clonal analysis
    Nature, 2012
    Co-Authors: Gregory Driessens, Benjamin Beck, Amelie Caauwe, Benjamin D Simons, Cedric Blanpain
    Abstract:

    Using genetic lineage tracing, tumour cells are traced in vivo in an unperturbed solid tumour; in a carcinogen-induced papilloma mouse model, cells in these benign lesions are found to mirror the clonal Hierarchy organization of normal tissue. Recent studies using the isolation of a subpopulation of tumour cells followed by their transplantation into immunodeficient mice provide evidence that certain tumours^ 1 , 2 , including squamous skin tumours^ 3 , 4 , 5 , contain cells with high clonogenic potential that have been referred to as cancer stem cells (CSCs). Until now, CSC properties have only been investigated by transplantation assays, and their existence in unperturbed tumour growth is unproven. Here we make use of clonal analysis of squamous skin tumours using genetic lineage tracing to unravel the mode of tumour growth in vivo in its native environment. To this end, we used a genetic labelling strategy that allows individual tumour cells to be marked and traced over time at different stages of tumour progression. Surprisingly, we found that the majority of labelled tumour cells in benign papilloma have only limited proliferative potential, whereas a fraction has the capacity to persist long term, giving rise to progeny that occupy a significant part of the tumour. As well as confirming the presence of two distinct proliferative cell compartments within the papilloma, mirroring the Composition, Hierarchy and fate behaviour of normal tissue, quantitative analysis of clonal fate data indicates that the more persistent population has stem-cell-like characteristics and cycles twice per day, whereas the second represents a slower cycling transient population that gives rise to terminally differentiated tumour cells. Such behaviour is shown to be consistent with double-labelling experiments and detailed clonal fate characteristics. By contrast, measurements of clone size and proliferative potential in invasive squamous cell carcinoma show a different pattern of behaviour, consistent with geometric expansion of a single CSC population with limited potential for terminal differentiation. This study presents the first experimental evidence for the existence of CSCs during unperturbed solid tumour growth. Using genetic-lineage tracing, Cedric Blanpain and colleagues for the first time clonally trace tumour cells in vivo in an unperturbed solid tumour. In a carcinogen-induced papilloma mouse model, they find that the cells in these benign lesions mirror the clonal Hierarchy organization of normal tissue. Only a fraction of papilloma cells with a higher proliferative potential is able to sustain a second, slower-cycling transient population that gives rise to the differentiated tumour cells that form the bulk of the papillomas. But when lesions progress to squamous cell carcinomas, there is a switch to mainly self-renewing divisions and limited differentiation, suggesting that these cells may represent a cancer stem cell population. Evidence for cancer stem cells — a subset of tumour cells able to maintain tumour growth — has previously been demonstrated only in solid tumours in transplantation experiments.