ems:FactTable

Metric entities: ems:Measure, ems:MeasureDistribution, ems:FactTable, ems:FactDistributionTable, ems:Map, ems:WorkBreakdownStructure

Description

Consider the work performed on a project. Work may be analyzed according to attributes such as who performed the work, the task or activity that the work accomplished, when the work was performed, etc. These attributes are referred to as dimensions.

Work may be quantified by such metrics as its effort in person-hours, its cost in some currency, its duration in months, its peak staffing, etc. These quantities are referred to as measures.

The term dimension is used because the measures can be regarded as occupying cells in a multi-dimensional array (sometimes referred to as a datacube). It is frequently of interest to summarize the measures along a dimension, for example given the effort by activity, calculate the total effort for all activities. Conversely, given the total effort, it may be of interest to see how it is broken down by activity.

In general, set of related measures, analyzed along a set of dimensions may be organized into a fact table. Each row of a fact table contains a set of measures (e.g. effort and cost) for a given combination of dimension values (e.g. activity and month). The ems:FactTable resource is used to represent fact tables.

This resource MAY contain the actual measurements, provide a link to the source of the actual measurements, or contain both a link to the source and a copy of the actual measurements obtained from the source (i.e. a cached copy of the source).

Properties

An ems:FactTable resource has the following properties:

Property	Range	Type	Occurrence	Edits	Description
dcterms:title	datatype	rdf:XMLLiteral	exactly-one	read-write	A short title for the fact table. Valid XHTML <span> element content.
ems:head	local inline resource	ems:Head	exactly-one	read-write	The head of the fact table.
ems:tableSource	resource	ems:FactTable	zero-or-one	read-write	An optional link to a source fact table that contains the facts.
ems:fact	local inline resource	ems:Fact	zero-or-more	read-write	A fact row in the fact table.

dcterms:title

This required property gives a short title for the fact table. Its datatype is XML literal and it MUST contain valid XHTML <span> element content.

ems:head

This required property contains an inline ems:Head resource that defines the columns of the fact table. The head of the table describes the data that the table contains. The head of the table may be defined before any measurements are available.

ems:tableSource

Fact tables contain actual measurements for projects. In practice, there may be many measurements and they may be updated frequently. The measurements may be at a finer level of granularity than the estimates, e.g. a project may estimate total defects found per month, whereas the actual number found may be collected daily. Furthermore, these measurements are often collected automatically by software development tools such as bug tracking systems or source code control systems. It may therefore be useful to simply refer to the source of the measurements rather than copy the actual measurements into the EMS 1.0 service provider, e.g. a dynamic query on a software tool may generate the fact table on demand.

The ems:tableSource property lets you refer to the remote source of the fact table data via a URL. An HTTP GET request on this URL MUST return an ems:FactTable resource whose dcterms:title and ems:head properties match this resource.

ems:fact

This multi-valued property refers to inline ems:Fact resources that are the rows of the fact table. There MAY be zero or more rows present in the fact table. If there is an ems:tableSource property, then the rows MUST be a copy of the data values received in the response of an HTTP GET request of the URL of the remote table source.

ems:Head

This inline resource defines the columns of a fact table. A fact table MUST have one or more dimension columns, e.g. date or role, and one or more measure columns, e.g. cost or effort. The dimension columns contain dimension values. Dimension columns SHOULD contain standard dimension values when they exist, e.g. for roles. The creator of the fact table MAY use custom dimension dimension values and record how these custom values are mapped to the standard values.

An ems:Head resource has the following properties:

Property	Range	Type	Occurrence	Edits	Description
ems:map	local inline resource	ems:Map	zero-or-more	read-write	A map from custom dimension values to standard dimension values.
ems:dimensionColumn	inline resource	ems:DimensionColumn	one-or-more	read-write	A dimension column.
ems:measureColumn	inline resource	ems:MeasureColumn	one-or-more	read-write	A measure column.

ems:map

This optional, multi-valued property provides an inline ems:Map resource that defines how custom dimension values are mapped to standard values. The scope of this mapping is local to the fact table.

ems:dimensionColumn

This required, multi-valued property provides an inline ems:DimensionColumn resource that defines a dimension column. Every fact table MUST have at least one dimension column.

ems:measureColumn

This required, multi-valued property provides an inline ems:MeasureColumn resource that defines a measure column. Every fact table MUST have at least one measure column.

ems:DimensionColumn

This inline resource describes a dimension column. Each ems:DimensionColumn resource in an RDF/XML document MUST have a unique identifier given by the rdf:ID attribute.

An ems:DimensionColumn resource has the following properties:

Property	Range	Type	Occurrence	Edits	Description
dcterms:title	datatype	rdf:XMLLiteral	exactly-one	read-write	A short title for the dimension column. Valid XHTML <span> element content.
ems:dimension	resource	rdf:Resource	exactly-one	read-write	A URI that identifies the dimension.
ems:grain	resource	rdf:Resource	exactly-one	read-write	A URI that identifies the grain of the dimension values.
ems:useMap	local resource	ems:Map	zero-or-one	read-write	The identifier of the mapping from custom to standard dimension values.

dcterms:title

This required property gives a short title for the dimension column. Its datatype is XML literal and it MUST contain valid XHTML <span> element content.

ems:dimension

The value of this required property is a URI that identifies the dimension, e.g. date or role. This SHOULD be a standard dimension identifier.

ems:grain

The value of this required property is a URI that identifies the grain of the dimension values, e.g. for date the grains are day, week, month, etc. This SHOULD be a standard dimension identifier.

ems:useMap

The value of this optional property is the local identifier of the ems:Map resource that defines the mapping from custom to standard dimensions values. The ems:Map resource MUST be defined as an inline resource in the ems:Head resource that contains this ems:DimensionColumn resource.

ems:MeasureColumn

This inline resource describes a measure column. Each ems:MeasureColumn resource in an RDF/XML document MUST have a unique identifier given by the rdf:ID attribute.

An ems:MeasureColumn resource has the following properties:

Property	Range	Type	Occurrence	Edits	Description
dcterms:title	datatype	rdf:XMLLiteral	exactly-one	read-write	A short title for the measure column. Valid XHTML <span> element content.
ems:metric	resource	ems:Metric	exactly-one	read-write	A URI that identifies the measure.
ems:unitOfMeasure	resource	ems:UnitOfMeasure	exactly-one	read-write	A URI that identifies the unit of measure.

dcterms:title

This required property gives a short title for the measure column. Its datatype is XML literal and it MUST contain valid XHTML <span> element content.

ems:metric

The value of this required property is a URI that identifies the measure, e.g. cost, effort, or size. This SHOULD be a standard dimension identifier.

ems:unitOfMeasure

The value of this required property is a URI that identifies the units of the measure values, e.g. for effort the units are person-hour, person-day, person-month, etc. This SHOULD be a standard dimension identifier.

ems:Fact

This inline resource defines a row of a fact table. It contains a set of dimension and measure cells. The dimension and measure cells MUST correspond exactly to the dimension and measure columns defined in the ems:Head resource of the fact table. Each dimension cell MUST refer to a unique dimension column and each dimension column MUST be referred to by a unique dimension cell. Each measure cell MUST refer to a unique measure column and each measure column MUST be referred to by a unique measure cell.

The correspondence between cells and columns is achieved in RDF/XML representations via resource identifiers. Each column defined in the head MUST have a unique identifier defined by an rdf:ID attribute. Each cell in a row MUST have an ems:inColumn property that refers to the column via an rdf:resource attribute.

An ems:Fact resource has the following properties:

Property	Range	Type	Occurrence	Edits	Description
ems:dimensionCell	local inline resource	ems:DimensionCell	one-or-more	read-write	A cell that holds a dimension value for a dimension column.
ems:measureCell	local inline resource	ems:MeasureCell	one-or-more	read-write	A cell that holds a measure value for a measure column.

ems:dimensionCell

The value of this required property in an inline ems:DimensionCell resource that holds the value of the dimension for a dimension column.

ems:measureCell

The value of this required property in an inline ems:MeasureCell resource that holds the value of the measure for a measure column.

ems:DimensionCell

This inline resource contains a dimension value in a row of a fact table.

It has the following properties:

Property	Range	Type	Occurrence	Edits	Description
ems:inColumn	resource	ems:DimensionColumn	exactly-one	read-write	The identifier of the dimension column of this cell.
ems:dimensionMember	resource	ems:DimensionMember	exactly-one	read-write	The dimension member for this cell. SHOULD be a standard URI if possible.

ems:inColumn

This required property is the identifier of the corresponding ems:DimensionColumn resource.

ems:dimensionMember

This required property is the dimension member. Standard dimension member URIs SHOULD be used if they exist.

ems:MeasureCell

This inline resource contains a measure value in a row of a fact table.

It has the following properties:

Property	Range	Type	Occurrence	Edits	Description
ems:inColumn	resource	ems:MeasureColumn	exactly-one	read-write	The identifier of the measure column of this cell.
ems:numericValue	datatype	xsd:double	exactly-one	read-write	The numeric value of the measure for this cell.

ems:inColumn

This required property is the identifier of the corresponding ems:MeasureColumn resource.

ems:numericValue

This required property is the numeric value of the measure.

Examples

• EMS 1.0 Primer, Listing of Defect Arrival Rate Measurements

Comments

Enter your comments here: