data_source.pl -- Cached data access

This module provides access to external data by caching it as a Prolog predicate. The data itself is kept in a global data module, so it is maintained over a SWISH Pengine invocation.

 data materialized(+Hash, +Signature, +SourceVersion) is det

Called by a data plugin to indicate that loading the data has finished.

Arguments:

Hash	- is the has of the original data source
Signature	- is a term Hash(Arg1, Arg2, ...), where Arg1, ... are atoms or small integers that indicate the field names.
SourceVersion	- is a term that indicates the identity of the source. this is typically a dict containing e.g., a time stamp, content hash, HTTP Etag value, etc.

 data_source(:Id, +Source) is det

Create a data source Id from the source definition Source. Source definitions are plugin files loaded from swish(data).

 record(:Id, -Record) is nondet

 data_record(:Id, -Record) is nondet

True when Record is a dict representing a row in the dataset identified by Id.

deprecated

- record/2 is deprecated. New code should use data_record/2.

 data_row(:Id, -Row) is nondet

 data_row(:Id, +Range, +Header, -Row) is nondet

True when Row is a term Id(Arg, ...), where the first row contains the column names.

Arguments:

Header

- If true, include a header row.

See also

- data_dump/3 to return a table and for a description of Range.

 data_dump(:Id, +Range, -Table) is det

Table is a list of rows in the indicated range. This cooperates with the table rendering to produce a data table. Range is one of:

all

All rows from the data are included. Be careful if these are many as it is likely to make your browser very slow.

From - To

List the (1-based) rows From to To

Count

If Count >= 0, list the first, else list the last Count rows.

 data_property(:Id, ?Property) is nondet

True when Property is a known property about the data source Id. Defined properties are:

columns(-Count)

Number of columns in the table.

column_names(-Names)

Names is a list of the column names as they appear in the data.

rows(-Rows)

Number of rows in the table

hash(-Hash)

Get the internal (hashed) identifier for the data source

source_version(-SourceVersion)

A term (often a dict) that provides version information about the source. Details depend on the source.

materialized(-TimeStamp)

The data source was materialized at TimeStamp.

source(-Term)

Description of the original source term used to declare the data source

 swish:goal_expansion(+Dict, -DataGoal)[multifile]

Translate a Dict where the tag is the identifier of a data source and the keys are columns pf this source into a goal on the data. Note that the data itself is represented as a Prolog predicate, representing each row as a fact and each column as an argument.

 data_flush(+Hash)

Drop the data associated with hash

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 data failed(Arg1, Arg2)

 data assert(Arg1)