The smallest meaningful element of data in a data source is referred to as a column (for relational data sources) or a field (for non-relational data sources). Column and field are used interchangeably throughout this content. Every column or field has several characteristics, such as the data type (character, date, integer, or some other type) and length or scale. Field characteristics can also include output display options, such as comma inclusion, currency symbol, date display, and so on. For consistency, all fields should be included in the metadata, so all users get the same view of the data. However, you can create a logical view of the data in which only a subset of the fields are available.
Certain fields in a data source may have a one-to-one relationship with each other and describe a group of related characteristics. For example, each unique ID number represents only one employee. These fields can be grouped together into a segment or, in relational terms, a table. You can relate segments to each other by creating a multi-segment data source or by joining segments together. Segments are the building blocks of larger data structures.
Fields can be categorized as measures (facts) or dimensions based on how they will be used in a request.
A measure or fact is a numeric value, such as Gross Profit or Cost of Goods Sold, that you may want to aggregate. All numeric values that can logically be summed are measures. Numeric fields that cannot be summed, such as product number and order ID, are not treated as measures. Instead, they may be used in the same way as dimension fields to analyze measures. It is up to you to understand your data and determine whether each numeric field should be summed. Related measures can be organized into measure groups. For example, Gross Profit and Cost of Goods Sold can be part of a Sales measure group.
A dimension is a way to categorize data. You can use a dimension to analyze and compare measures. Generally, any field that is not a measure, usually an alphanumeric field such as product, is a dimension. Dimensions can be organized into hierarchies to define the relationships between the fields in the hierarchies. For example, a Geography hierarchy can contain the Continent, Country, State, and City dimensions. You can also define dimension fields that are not part of a dimension hierarchy.
An attribute is a collection of related objects in a dimension. For example, in the Model dimension, there are attributes for Brand, Brand Type, and Product Name. Attributes are specific to a dimension and are typically more specific than general in nature.
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