Contains the interface definitions of the {@link org.knime.core.data.DataCell} and {@link org.knime.core.data.DataTable} and related classes, used to store and access the actual data.

A {@link org.knime.core.data.DataTable DataTable} is used to pass data along between nodes in the workflow.

It has rows and columns. The number of columns is fixed. The type of data stored in each column is well defined, and each column has a unique name. Each row consists of a certain number of cells (which contain the actual data) and a unique row identifier. The data in a {@link org.knime.core.data.DataTable DataTable} is read-only.

A {@link org.knime.core.data.DataTable DataTable} contains a {@link org.knime.core.data.DataTableSpec DataTableSpec} object which describes the structure of the table (the number of columns, the column types, etc.) and a {@link org.knime.core.data.RowIterator RowIterator} which allows to iterate over the rows of the table and actually access the data.

The iterator returns {@link org.knime.core.data.DataRow DataRow}s, that allow access to all {@link org.knime.core.data.DataCell DataCell}s in this row by index (the index of the column). The number of rows is usually not known in advance (not in all tables), the iterator indicates when it reaches the end of the table. As the source underlying the table could be sequential and of arbitrary size, the general {@link org.knime.core.data.DataTable DataTable} interface doesn't provide any random access methods.

The {@link org.knime.core.data.DataTableSpec DataTableSpec} contains the meta information of the data table. It can be used to query the columns' name and type, and the number of columns. In addition to that it is also used to pass information along to connected successors to let them know of the structure of the table to come. So, if the successor's preparations for execution (like the settings) depend on the structure of the data table of the predecessor, it can be set up after it received the {@link org.knime.core.data.DataTableSpec DataTableSpec}.

Accessing the data in a DataTable

{@link org.knime.core.data.DataCell DataCell}s are of certain type, depending on the type of data appearing in the corresponding column. For each data cell type certain objects exist describing the cell's properties, capabilities and compatibilities. This is the {@link org.knime.core.data.DataCell DataCell} derivative implementing {@link org.knime.core.data.DataValue DataValue}, which defines how to access the value stored in the data cell.

Read more on data cells here and in the FAQ.

Default implementations of {@link org.knime.core.data.DataCell DataCell}s can be found in the org.knime.core.data.def package. These implementations store the value of the cell in a member of the corresponding Java data type.

{@link org.knime.core.data.DataTable DataTable}s could be arbitrary big, thus they shouldn't be copied or held in memory.