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NAME ^

Muldis::D::Manual::CD - Simple CD database example

VERSION ^

This document is Muldis::D::Manual::CD version 0.9.0.

PREFACE ^

This document is part of the Muldis D language and implementations manual, whose root document is Muldis::D::Manual; you should read that root document before you read this one, which provides subservient details.

DESCRIPTION ^

This example code demonstrates a very basic CD database, which consists of a schema definition having relvars to store data and routines to fetch or update that data, and it includes some sample data.

This schema definition, routines, and sample data are heavily based on the contents of DBIx::Class::Manual::Example; they are essentially the same except for optimizations towards perceived better practice for Muldis D.

The database consists of the following:

    - relvar 'artists' with attributes: artist_id, artist_name
    - relvar 'cds'     with attributes: cd_id, artist_id, cd_title
    - relvar 'tracks'  with attributes: track_id, cd_id, track_title

And these rules exist:

    - one artist can have many cds
    - one cd belongs to one artist
    - one cd can have many tracks
    - one track belongs to one cd

In an effort to keep this example more realistic, the code is divided into 3 depots:

the_database

This is what you would traditionally call the database. It represents the state of a newly created depot that has the relvar and access routine definitions freshly installed in its catalog section, and corresponding relvars in its data section which are empty.

insert_db

This is a program which inserts some test data into the_database.

test_db

This is a program which queries the_database and prints out its findings for the user to see.

This document has 3 main copies of the example, one in each of the 3 standard dialects of Muldis D.

But while the PTMD_STD dialect's copy of the example is complete, the HDMD_Perl6_STD and HDMD_Perl5_STD dialects' copies of the example are each missing the bodies of 13 routines, and have just the headings/signatures for those 13; the HDMD_Perl6_STD and HDMD_Perl5_STD dialects' copies of the example are otherwise complete, having the complete definitions of 7 routines, and all of the type definitions, constraints, scaffolding, and data. The PTMD_STD copy is, in any event, the most terse and readable, especially for routine definitions; the routines that are complete in the 2 Perl-STD copies should constitute a representative subset, such that one should be able to infer the missing routine bodies easily enough through comparison with the complete PTMD_STD copy; but the other routines might also be made complete later if the rationale exists.

EXAMPLE USING PTMD_STD DIALECT ^

PTMD_STD - the_database

    Muldis_D:"http://muldis.com":0.137.0:PTMD_STD:{
        catalog_abstraction_level => rtn_inv_alt_syn,
        op_char_repertoire => basic
    }

    depot-catalog {
        self-local-dbvar-type nlx.lib.""

    #######################################################################

    database-type "" {
        attr artists : nlx.lib.artists
        attr cds     : nlx.lib.cds
        attr tracks  : nlx.lib.tracks
        constraint nlx.lib.sc_artist_has_cds
        constraint nlx.lib.sc_cd_has_tracks
    }

    #######################################################################

    relation-type artists {
        tuple-type nlx.lib.T
        with tuple-type T {
            attr artist_id   : Int
            attr artist_name : Text
        }
        constraint nlx.lib.pk
        with primary-key pk { artist_id }
        constraint nlx.lib.sk_artist_name
        with key-constraint sk_artist_name { artist_name }
    }

    #######################################################################

    relation-type cds {
        tuple-type nlx.lib.T
        with tuple-type T {
            attr cd_id     : Int
            attr artist_id : Int
            attr cd_title  : Text
        }
        constraint nlx.lib.pk
        with primary-key pk { cd_id }
        constraint nlx.lib.sk_cd_title
        with key-constraint sk_cd_title { cd_title }
    }

    subset-constraint sc_artist_has_cds {
        parent artists using-key nlx.lib.artists.pk
        child cds using-attrs { =>artist_id }
    }

    #######################################################################

    relation-type tracks {
        tuple-type nlx.lib.T
        with tuple-type T {
            attr track_id    : Int
            attr cd_id       : Int
            attr track_title : Text
        }
        constraint nlx.lib.pk
        with primary-key pk { track_id }
        constraint nlx.lib.sk_track_title
        with key-constraint sk_track_title { track_title }
    }

    subset-constraint sc_cd_has_tracks {
        parent cds using-key nlx.lib.cds.pk
        child tracks using-attrs { =>cd_id }
    }

    #######################################################################

    recipe get_tracks_by_cd (&track_titles : array_of.Text,
            cd_title : Text, db ::= nlx.data) {
        track_titles := Array_from_attr( db.tracks matching (
            db.cds matching @:{ { =>cd_title } }
        ), name => Name:track_title )
    }

    recipe get_tracks_by_artist (&track_titles : array_of.Text,
            artist_name : Text, db ::= nlx.data) {
        track_titles := Array_from_attr( db.tracks matching (
            db.cds matching (db.artists matching @:{ { =>artist_name } })
        ), name => Name:track_title )
    }

    #######################################################################

    recipe get_cd_by_track (&cd_title : maybe_of.Text,
            track_title : Text, db ::= nlx.data) {
        cd_title := Set_from_attr( db.cds matching (
            db.tracks matching @:{ { =>track_title } }
        ), name => Name:cd_title )
    }

    recipe get_cds_by_artist (&cd_titles : array_of.Text,
            artist_name : Text, db ::= nlx.data) {
        cd_titles := Array_from_attr( db.cds matching (
            db.artists matching @:{ { =>artist_name } }
        ), name => Name:cd_title )
    }

    #######################################################################

    recipe get_artist_by_track (&artist_name : maybe_of.Text,
            track_title : Text, db ::= nlx.data) {
        artist_name := Set_from_attr( db.artists matching (
            db.cds matching (db.tracks matching @:{ { =>track_title } })
        ), name => Name:artist_name )
    }

    recipe get_artist_by_cd (&artist_name : maybe_of.Text,
            cd_title : Text, db ::= nlx.data) {
        artist_name := Set_from_attr( db.artists matching (
            db.cds matching @:{ { =>cd_title } }
        ), name => Name:artist_name )
    }

    #######################################################################

    } #`depot-catalog`#

    depot-data Database:{
        artists => @:{ artist_id, artist_name },
        cds     => @:{ cd_id, artist_id, cd_title },
        tracks  => @:{ track_id, cd_id, track_title }
    } #`depot-data`#

PTMD_STD - insert_db

    Muldis_D:"http://muldis.com":0.137.0:PTMD_STD:{
        catalog_abstraction_level => rtn_inv_alt_syn,
        op_char_repertoire => basic
    }

    depot-catalog {
        self-local-dbvar-type Database

        stimulus-response-rule bootstrap {
            when after-mount
            invoke main
        }

    #######################################################################

    procedure main () [
        #`Connect to the_database in read-write mode.
          The "..." has likes of filename, server name, user, pass, etc.`#
        create_depot_mount( name => Name:db, we_may_update => True,
            details => @:OVLScaValExprNodeSet:{ ... } )

        #`Add test data to the_database, as a single atomic transaction.
          This might fail if records with same titles/etc already there.`#
        try
            nlx.lib.insert_records()
        catch
            nlx.lib.insert_failed()

        #`Disconnect the_database now that we're done with it.`#
        drop_depot_mount( name => Name:db )
    ]

    procedure insert_failed (err : Exception) [
        write_Text_line( 'Failed to insert, maybe because of duplicates.' )
    ]

    #######################################################################

    recipe insert_records (&db ::= fed.data.db, src ::= nlx.data) {
        #`We will generate new integer record ids serially starting after
          the maximum ids currently in use per relvar.
          There are, of course, other ways to produce record ids.`#

        #`So start by determining the existing maximum ids.`#
        max_used_artist_id ::= is_empty(db.artists) ?? 0
            !! max( Set_from_attr( db.artists, name => Name:artist_id ) )
        max_used_cd_id ::= is_empty(db.cds) ?? 0
            !! max( Set_from_attr( db.cds, name => Name:cd_id ) )
        max_used_track_id ::= is_empty(db.tracks) ?? 0
            !! max( Set_from_attr( db.tracks, name => Name:track_id ) )

        #`Now generate new record ids and attach them to records to add.
          The process involves sorting of the new data simply to make it
          fully-deterministic, giving same result on any implementation.`#
        src_artists_with_ids ::= rank_by_attr_names( src.artists,
            name => Name:artist_id,
            order_by => [ %:{ name => Name:artist_name,
                is_reverse_order => False } ],
            first_rank => max_used_artist_id ++
        )
        src_cds_with_ids ::= rank_by_attr_names( src.cds,
            name => Name:cd_id,
            order_by => [ %:{ name => Name:cd_title,
                is_reverse_order => False } ],
            first_rank => max_used_cd_id ++
        )
        src_tracks_with_ids ::= rank_by_attr_names( src.tracks,
            name => Name:track_id,
            order_by => [ %:{ name => Name:track_title,
                is_reverse_order => False } ],
            first_rank => max_used_track_id ++
        )

        #`Now substitute parent record ids for parent names or titles.`#
        new_artists ::= src_artists_with_ids
        new_cds ::= src_cds_with_ids compose new_artists
        new_tracks ::= src_tracks_with_ids compose new_cds{!artist_id}

        #`Now insert the prepared new records into the_database.`#
        db.artists :=union new_artists
        db.cds :=union new_cds
        db.tracks :=union new_tracks
    }

    #######################################################################

    } #`depot-catalog`#

    depot-data Database:{
        artists => @:[ artist_name ];{
            [ 'Michael Jackson' ],
            [ 'Eminem'          ]
        },
        cds => @:[ cd_title, artist_name ];{
            [ 'Thriller'               , 'Michael Jackson' ],
            [ 'Bad'                    , 'Michael Jackson' ],
            [ 'The Marshall Mathers LP', 'Eminem'          ]
        },
        tracks => @:[ track_title, cd_title ];{
            [ 'Beat It'        , 'Thriller'                ],
            [ 'Billie Jean'    , 'Thriller'                ],
            [ 'Dirty Diana'    , 'Bad'                     ],
            [ 'Smooth Criminal', 'Bad'                     ],
            [ 'Leave Me Alone' , 'Bad'                     ],
            [ 'Stan'           , 'The Marshall Mathers LP' ],
            [ 'The Way I Am'   , 'The Marshall Mathers LP' ]
        }
    } #`depot-data`#

PTMD_STD - test_db

    Muldis_D:"http://muldis.com":0.137.0:PTMD_STD:{
        catalog_abstraction_level => rtn_inv_alt_syn,
        op_char_repertoire => basic
    }

    depot-catalog {
        stimulus-response-rule bootstrap {
            when after-mount
            invoke main
        }

    #######################################################################

    procedure main () [
        #`Connect to the_database in read-only mode.
          The "..." has likes of filename, server name, user, pass, etc.`#
        create_depot_mount( name => Name:db,
            details => @:OVLScaValExprNodeSet:{ ... } )

        #`Fetch test data, in a transaction for read-consistency.`#
        nlx.lib.get_records()

        #`Disconnect the_database now that we're done with it.`#
        drop_depot_mount( name => Name:db )
    ]

    #######################################################################

    transaction get_records () [
        nlx.lib.get_tracks_by_cd( cd_title => 'Bad' )
        nlx.lib.get_tracks_by_artist( artist_name => 'Michael Jackson' )

        nlx.lib.get_cd_by_track( track_title => 'Stan' )
        nlx.lib.get_cds_by_artist( artist_name => 'Michael Jackson' )

        nlx.lib.get_artist_by_track( track_title => 'Dirty Diana' )
        nlx.lib.get_artist_by_cd( cd_title => 'The Marshall Mathers LP' )
    ]

    #######################################################################

    procedure disp_list (h1 : Text, h2 : Text, list : array_of.Text) [
        var eol : Text
        end_of_line_Text( &eol )
        var msg : Text
        { msg := h1 ~ '(' ~ h2 ~ '):'
            ~ eol ~ cat_with_sep( list, sep => eol ) ~ eol ~ eol }
        write_Text( msg )
    ]

    procedure disp_item (h1 : Text, h2 : Text, item : maybe_of.Text) [
        var h : Text
        var v : Text
        {
            h := h1 ~ '(' ~ h2 ~ '):'
            v := item // '<No Match!>'
        }
        write_Text_line( h )
        write_Text_line( v )
        write_Text_line()
    ]

    #######################################################################

    procedure get_tracks_by_cd (cd_title : Text) [
        var track_titles : array_of.Text
        fed.lib.db.get_tracks_by_cd( &=>track_titles, =>cd_title )
        nlx.lib.disp_list( h1 => 'get_tracks_by_cd',
            h2 => cd_title, list => track_titles )
    ]

    procedure get_tracks_by_artist (artist_name : Text) [
        var track_titles : array_of.Text
        fed.lib.db.get_tracks_by_artist( &=>track_titles, =>artist_name )
        nlx.lib.disp_list( h1 => 'get_tracks_by_artist',
            h2 => artist_name, list => track_titles )
    ]

    #######################################################################

    procedure get_cd_by_track (track_title : Text) [
        var cd_title : maybe_of.Text
        fed.lib.db.get_cd_by_track( &=>cd_title, =>track_title )
        nlx.lib.disp_item( h1 => 'get_cd_by_track',
            h2 => track_title, item => cd_title )
    ]

    procedure get_cds_by_artist (artist_name : Text) [
        var cd_titles : array_of.Text
        fed.lib.db.get_cds_by_artist( &=>cd_titles, =>artist_name )
        nlx.lib.disp_list( h1 => 'get_cds_by_artist',
            h2 => artist_name, list => cd_titles )
    ]

    #######################################################################

    procedure get_artist_by_track (track_title : Text) [
        var artist_name : maybe_of.Text
        fed.lib.db.get_artist_by_track( &=>artist_name, =>track_title )
        nlx.lib.disp_item( h1 => 'get_artist_by_track',
            h2 => track_title, item => artist_name )
    ]

    procedure get_artist_by_cd (cd_title : Text) [
        var artist_name : maybe_of.Text
        fed.lib.db.get_artist_by_cd( &=>artist_name, =>cd_title )
        nlx.lib.disp_item( h1 => 'get_artist_by_cd',
            h2 => cd_title, item => artist_name )
    ]

    #######################################################################

    } #`depot-catalog`#

EXAMPLE USING HDMD_Perl6_STD DIALECT ^

HDMD_Perl6_STD - the_database

    [
        [ 'Muldis_D', 'http://muldis.com', '0.137.0', 'HDMD_Perl6_STD', {
            catalog_abstraction_level => 'rtn_inv_alt_syn',
            op_char_repertoire => 'basic'
        } ],

        [ 'depot',
            :depot-catalog[
                :self-local-dbvar-type<nlx.lib.>,

    #######################################################################

    [ 'database-type', '', [
        [ 'attr', 'artists', 'nlx.lib.artists' ],
        [ 'attr', 'cds'    , 'nlx.lib.cds'     ],
        [ 'attr', 'tracks' , 'nlx.lib.tracks'  ],
        :constraint<nlx.lib.sc_artist_has_cds>,
        :constraint<nlx.lib.sc_cd_has_tracks>,
    ] ],

    #######################################################################

    [ 'relation-type', 'artists', [
        :tuple-type<nlx.lib.T>,
        :with[ 'tuple-type', 'T', [
            [ 'attr', 'artist_id'  , 'Int'  ],
            [ 'attr', 'artist_name', 'Text' ],
        ] ],
        :constraint<nlx.lib.pk>,
        :with[ 'primary-key', 'pk', 'artist_id' ],
        :constraint<nlx.lib.sk_artist_name>,
        :with[ 'key-constraint', 'sk_artist_name', 'artist_name' ],
    ] ],

    #######################################################################

    [ 'relation-type', 'cds', [
        :tuple-type<nlx.lib.T>,
        :with[ 'tuple-type', 'T', [
            [ 'attr', 'cd_id'    , 'Int'  ],
            [ 'attr', 'artist_id', 'Int'  ],
            [ 'attr', 'cd_title' , 'Text' ],
        ] ],
        :constraint<nlx.lib.pk>,
        :with[ 'primary-key', 'pk', 'cd_id' ],
        :constraint<nlx.lib.sk_cd_title>,
        :with[ 'key-constraint', 'sk_cd_title', 'cd_title' ],
    ] ],

    [ 'subset-constraint', 'sc_artist_has_cds', {
        parent      => 'artists',
        using-key   => 'nlx.lib.artists.pk',
        child       => 'cds',
        using-attrs => { artist_id => 'artist_id' }
    } ],

    #######################################################################

    [ 'relation-type', 'tracks', [
        :tuple-type<nlx.lib.T>,
        :with[ 'tuple-type', 'T', [
            [ 'attr', 'track_id'   , 'Int'  ],
            [ 'attr', 'cd_id'      , 'Int'  ],
            [ 'attr', 'track_title', 'Text' ],
        ] ],
        :constraint<nlx.lib.pk>,
        :with[ 'primary-key', 'pk', 'track_id' ],
        :constraint<nlx.lib.sk_track_title>,
        :with[ 'key-constraint', 'sk_track_title', 'track_title' ],
    ] ],

    [ 'subset-constraint', 'sc_cd_has_tracks', {
        parent      => 'cds',
        using-key   => 'nlx.lib.cds.pk',
        child       => 'tracks',
        using-attrs => { cd_id => 'cd_id' }
    } ],

    #######################################################################

    [ 'recipe', 'get_tracks_by_cd',
        { track_titles => ['&','array_of.Text'], cd_title => 'Text',
        db => ['::=','nlx.data'] } => '...' ],

    [ 'recipe', 'get_tracks_by_artist',
        { track_titles => ['&','array_of.Text'], artist_name => 'Text',
        db => ['::=','nlx.data'] } => '...' ],

    [ 'recipe', 'get_tracks_by_artist',
            { track_titles => ['&','array_of.Text'],
            artist_name => 'Text', db => ['::=','nlx.data'] } => [
        [ 'op', ':=', [ :d<track_titles>,
            [ 'curried-func', 'Array_from_attr', [
                [ 'op', 'matching', [ :acc<db.tracks>,
                    [ 'op', 'matching', [ :acc<db.cds>,
                        [ 'op', 'matching', [ :acc<db.artists>,
                            '@' => Set.new(
                                { artist_name => :d<artist_name> }
                            )
                        ] ]
                    ] ]
                ] ]
            ], { name => :Name<track_title> } ]
        ] ],
    ] ],

    #######################################################################

    [ 'recipe', 'get_cd_by_track', { cd_title => ['&','maybe_of.Text'],
        track_title => 'Text', db => ['::=','nlx.data'] } => '...' ],

    [ 'recipe', 'get_cds_by_artist', { cd_titles => ['&','array_of.Text'],
        artist_name => 'Text', db => ['::=','nlx.data'] } => '...' ],

    #######################################################################

    [ 'recipe', 'get_artist_by_track',
        { artist_name => ['&','maybe_of.Text'], track_title => 'Text',
        db => ['::=','nlx.data'] } => '...' ],

    [ 'recipe', 'get_artist_by_cd', { artist_name => ['&','maybe_of.Text'],
        cd_title => 'Text', db => ['::=','nlx.data'] } => '...' ],

    #######################################################################

            ], # depot-catalog #

            :depot-data[ 'Database', {
                artists => '@' => Set.new(<artist_id artist_name>),
                cds     => '@' => Set.new(<cd_id artist_id cd_title>),
                tracks  => '@' => Set.new(<track_id cd_id track_title>)
            } ] # depot-data #
        ]
    ]

HDMD_Perl6_STD - insert_db

    [
        [ 'Muldis_D', 'http://muldis.com', '0.137.0', 'HDMD_Perl6_STD', {
            catalog_abstraction_level => 'rtn_inv_alt_syn',
            op_char_repertoire => 'basic'
        } ],

        [ 'depot',
            :depot-catalog[
                :self-local-dbvar-type<Database>,

                ['stimulus-response-rule','bootstrap',:after-mount<main>],

    #######################################################################

    [ 'procedure', 'main', {} => [
        # Connect to the_database in read-write mode. #
        # The "..." has likes of filename, server name, user, pass, etc. #
        [ 'iproc-imp-invo', 'create_depot_mount', { name => :Name<db>,
            we_may_update => Bool::True,
            details => [ '@', 'OVLScaValExprNodeSet', '...' ] } ],

        # Add test data to the_database, as a single atomic transaction. #
        # This might fail if records with same titles/etc already there. #
        [ 'try-catch',
            :iproc-imp-invo<nlx.lib.insert_records>,
            :iproc-imp-invo<nlx.lib.insert_failed>
        ],

        # Disconnect the_database now that we're done with it. #
        [ 'iproc-imp-invo', 'drop_depot_mount', { name => :Name<db> } ],
    ] ],

    [ 'procedure', 'insert_failed', { err => 'Exception' } => [
        [ 'iproc-imp-invo', 'write_Text_line',
            [ 'Failed to insert, maybe because of duplicates.' ] ]
    ] ],

    #######################################################################

    [ 'recipe', 'insert_records', { db => ['&','::=','fed.data.db'],
        src => ['::=','nlx.data'] } => '...' ],

    #######################################################################

            ], # depot-catalog #

            :depot-data[ 'Database', {
                artists => '@' => <artist_name> => Set.new(
                    [ 'Michael Jackson' ],
                    [ 'Eminem'          ]
                ),
                cds => '@' => <cd_title artist_name> => Set.new(
                    [ 'Thriller'               , 'Michael Jackson' ],
                    [ 'Bad'                    , 'Michael Jackson' ],
                    [ 'The Marshall Mathers LP', 'Eminem'          ]
                ),
                tracks => '@' => <track_title cd_title> => Set.new(
                    [ 'Beat It'        , 'Thriller'                ],
                    [ 'Billie Jean'    , 'Thriller'                ],
                    [ 'Dirty Diana'    , 'Bad'                     ],
                    [ 'Smooth Criminal', 'Bad'                     ],
                    [ 'Leave Me Alone' , 'Bad'                     ],
                    [ 'Stan'           , 'The Marshall Mathers LP' ],
                    [ 'The Way I Am'   , 'The Marshall Mathers LP' ]
                )
            } ] # depot-data #
        ]
    ]

HDMD_Perl6_STD - test_db

    [
        [ 'Muldis_D', 'http://muldis.com', '0.137.0', 'HDMD_Perl6_STD', {
            catalog_abstraction_level => 'rtn_inv_alt_syn',
            op_char_repertoire => 'basic'
        } ],

        [ 'depot',
            :depot-catalog[
                ['stimulus-response-rule','bootstrap',:after-mount<main>],

    #######################################################################

    [ 'procedure', 'main', {} => [
        # Connect to the_database in read-only mode. #
        # The "..." has likes of filename, server name, user, pass, etc. #
        [ 'iproc-imp-invo', 'create_depot_mount', { name => :Name<db>,
            details => [ '@', 'OVLScaValExprNodeSet', '...' ] } ],

        # Fetch test data, in a transaction for read-consistency. #
        :iproc-imp-invo<nlx.lib.get_records>,

        # Disconnect the_database now that we're done with it. #
        [ 'iproc-imp-invo', 'drop_depot_mount', { name => :Name<db> } ],
    ] ],

    #######################################################################

    [ 'transaction', 'get_records', {} => [
        [ 'iproc-imp-invo', 'nlx.lib.get_tracks_by_cd',
            { cd_title => 'Bad' } ],
        [ 'iproc-imp-invo', 'nlx.lib.get_tracks_by_artist',
            { artist_name => 'Michael Jackson' } ],

        [ 'iproc-imp-invo', 'nlx.lib.get_cd_by_track',
            { track_title => 'Stan' } ],
        [ 'iproc-imp-invo', 'nlx.lib.get_cds_by_artist',
            { artist_name => 'Michael Jackson' } ],

        [ 'iproc-imp-invo', 'nlx.lib.get_artist_by_track',
            { track_title => 'Dirty Diana' } ],
        [ 'iproc-imp-invo', 'nlx.lib.get_artist_by_cd',
            { cd_title => 'The Marshall Mathers LP' } ],
    ] ],

    #######################################################################

    [ 'procedure', 'disp_list', { h1 => 'Text', h2 => 'Text',
            list => 'array_of.Text' } => [
        [ 'var', 'eol', 'Text' ],
        [ 'iproc-imp-invo', 'end_of_line_Text', [ ['&',:d<eol>] ] ],
        [ 'var', 'msg', 'Text' ],
        :atomic-stmt[
            [ 'op', ':=', [ :d<msg>, [ 'op', '~', [
                :d<h1>, '(', :d<h2>, '):',
                :d<eol>,
                [ 'func-invo', 'cat_with_sep', [ :d<list> ],
                    { 'sep' => :d<eol> } ],
                :d<eol>, :d<eol>
            ] ] ] ]
        ],
        [ 'iproc-imp-invo', 'write_Text', [ :d<msg> ] ],
    ] ],

    [ 'procedure', 'disp_item', { h1 => 'Text', h2 => 'Text',
        item => 'maybe_of.Text' } => '...' ],

    #######################################################################

    [ 'procedure', 'get_tracks_by_cd', { cd_title => 'Text' } => '...' ],

    [ 'procedure', 'get_tracks_by_artist', { artist_name => 'Text' } => [
        [ 'var', 'track_titles', 'array_of.Text' ],
        [ 'iproc-imp-invo', 'fed.lib.db.get_tracks_by_artist',
            { track_titles => ['&',:d<track_titles>],
            artist_name => :d<artist_name> } ],
        [ 'iproc-imp-invo', 'nlx.lib.disp_list',
            { h1 => 'get_tracks_by_artist', h2 => :d<artist_name>,
            list => :d<track_titles> } ],
    ] ],

    #######################################################################

    [ 'procedure', 'get_cd_by_track', { track_title => 'Text' } => '...' ],

    [ 'procedure', 'get_cds_by_artist', {artist_name => 'Text'} => '...' ],

    #######################################################################

    [ 'procedure', 'get_artist_by_track', {track_title=>'Text'} => '...' ],

    [ 'procedure', 'get_artist_by_cd', { cd_title => 'Text' } => '...' ],

    #######################################################################

            ] # depot-catalog #
        ]
    ]

EXAMPLE USING HDMD_Perl5_STD DIALECT ^

HDMD_Perl5_STD - the_database

    [
        [ 'Muldis_D', 'http://muldis.com', '0.137.0', 'HDMD_Perl5_STD', {
            catalog_abstraction_level => 'rtn_inv_alt_syn',
            op_char_repertoire => 'basic'
        } ],

        [ 'depot',
            [ 'depot-catalog' => [
                [ 'self-local-dbvar-type', 'nlx.lib.' ],

    #######################################################################

    [ 'database-type', '', [
        [ 'attr', 'artists', 'nlx.lib.artists' ],
        [ 'attr', 'cds'    , 'nlx.lib.cds'     ],
        [ 'attr', 'tracks' , 'nlx.lib.tracks'  ],
        [ 'constraint', 'nlx.lib.sc_artist_has_cds' ],
        [ 'constraint', 'nlx.lib.sc_cd_has_tracks'  ],
    ] ],

    #######################################################################

    [ 'relation-type', 'artists', [
        [ 'tuple-type', 'nlx.lib.T' ],
        [ 'with' => [ 'tuple-type', 'T', [
            [ 'attr', 'artist_id'  , 'Int'  ],
            [ 'attr', 'artist_name', 'Text' ],
        ] ] ],
        [ 'constraint', 'nlx.lib.pk' ],
        [ 'with' => [ 'primary-key', 'pk', 'artist_id' ] ],
        [ 'constraint', 'nlx.lib.sk_artist_name' ],
        [ 'with' => [ 'key-constraint','sk_artist_name','artist_name' ] ],
    ] ],

    #######################################################################

    [ 'relation-type', 'cds', [
        [ 'tuple-type', 'nlx.lib.T' ],
        [ 'with' => [ 'tuple-type', 'T', [
            [ 'attr', 'cd_id'    , 'Int'  ],
            [ 'attr', 'artist_id', 'Int'  ],
            [ 'attr', 'cd_title' , 'Text' ],
        ] ] ],
        [ 'constraint', 'nlx.lib.pk' ],
        [ 'with' => [ 'primary-key', 'pk', 'cd_id' ] ],
        [ 'constraint', 'nlx.lib.sk_cd_title' ],
        [ 'with' => [ 'key-constraint', 'sk_cd_title', 'cd_title' ] ],
    ] ],

    [ 'subset-constraint', 'sc_artist_has_cds', {
        parent        => 'artists',
        'using-key'   => 'nlx.lib.artists.pk',
        child         => 'cds',
        'using-attrs' => { artist_id => 'artist_id' }
    } ],

    #######################################################################

    [ 'relation-type', 'tracks', [
        [ 'tuple-type', 'nlx.lib.T' ],
        [ 'with' => [ 'tuple-type', 'T', [
            [ 'attr', 'track_id'   , 'Int'  ],
            [ 'attr', 'cd_id'      , 'Int'  ],
            [ 'attr', 'track_title', 'Text' ],
        ] ] ],
        [ 'constraint', 'nlx.lib.pk' ],
        [ 'with' => [ 'primary-key', 'pk', 'track_id' ] ],
        [ 'constraint', 'nlx.lib.sk_track_title' ],
        [ 'with' => [ 'key-constraint','sk_track_title','track_title' ] ],
    ] ],

    [ 'subset-constraint', 'sc_cd_has_tracks', {
        parent        => 'cds',
        'using-key'   => 'nlx.lib.cds.pk',
        child         => 'tracks',
        'using-attrs' => { cd_id => 'cd_id' }
    } ],

    #######################################################################

    [ 'recipe', 'get_tracks_by_cd',
        [ { track_titles => ['&','array_of.Text'], cd_title => 'Text',
        db => ['::=','nlx.data'] } => '...' ] ],

    [ 'recipe', 'get_tracks_by_artist',
            [ { track_titles => ['&','array_of.Text'],
            artist_name => 'Text', db => ['::=','nlx.data'] } => [
        [ 'op', ':=', [ ['d','track_titles'],
            [ 'curried-func', 'Array_from_attr', [
                [ 'op', 'matching', [ ['acc','db.tracks'],
                    [ 'op', 'matching', [ ['acc','db.cds'],
                        [ 'op', 'matching', [ ['acc','db.artists'],
                            [ '@', [{artist_name => ['d','artist_name']}] ]
                        ] ]
                    ] ]
                ] ]
            ], { name => ['Name','track_title'] } ]
        ] ],
    ] ] ],

    #######################################################################

    [ 'recipe', 'get_cd_by_track',
        [ { cd_title => ['&','maybe_of.Text'], track_title => 'Text',
        db => ['::=','nlx.data'] } => '...' ] ],

    [ 'recipe', 'get_cds_by_artist',
        [ { cd_titles => ['&','array_of.Text'], artist_name => 'Text',
        db => ['::=','nlx.data'] } => '...' ] ],

    #######################################################################

    [ 'recipe', 'get_artist_by_track',
        [ { artist_name => ['&','maybe_of.Text'], track_title => 'Text',
        db => ['::=','nlx.data'] } => '...' ] ],

    [ 'recipe', 'get_artist_by_cd',
        [ { artist_name => ['&','maybe_of.Text'], cd_title => 'Text',
        db => ['::=','nlx.data'] } => '...' ] ],

    #######################################################################

            ] ], # depot-catalog #

            [ 'depot-data' => [ 'Database', {
                artists => ['@',['artist_id','artist_name']],
                cds     => ['@',['cd_id','artist_id','cd_title']],
                tracks  => ['@',['track_id','cd_id','track_title']]
            } ] ] # depot-data #
        ]
    ]

HDMD_Perl5_STD - insert_db

    [
        [ 'Muldis_D', 'http://muldis.com', '0.137.0', 'HDMD_Perl5_STD', {
            catalog_abstraction_level => 'rtn_inv_alt_syn',
            op_char_repertoire => 'basic'
        } ],

        [ 'depot',
            [ 'depot-catalog' => [
                [ 'self-local-dbvar-type', 'Database' ],

                [ 'stimulus-response-rule', 'bootstrap',
                    ['after-mount' => 'main'] ],

    #######################################################################

    [ 'procedure', 'main', [ {} => [
        # Connect to the_database in read-write mode. #
        # The "..." has likes of filename, server name, user, pass, etc. #
        [ 'iproc-imp-invo', 'create_depot_mount', { name => ['Name','db'],
            we_may_update => ['Bool','True'],
            details => [ '@', 'OVLScaValExprNodeSet', '...' ] } ],

        # Add test data to the_database, as a single atomic transaction. #
        # This might fail if records with same titles/etc already there. #
        [ 'try-catch',
            [ 'iproc-imp-invo', 'nlx.lib.insert_records' ],
            [ 'iproc-imp-invo', 'nlx.lib.insert_failed' ]
        ],

        # Disconnect the_database now that we're done with it. #
        [ 'iproc-imp-invo', 'drop_depot_mount', {name => ['Name','db']} ],
    ] ] ],

    [ 'procedure', 'insert_failed', [ { err => 'Exception' } => [
        [ 'iproc-imp-invo', 'write_Text_line',
            [ 'Failed to insert, maybe because of duplicates.' ] ]
    ] ] ],

    #######################################################################

    [ 'recipe', 'insert_records', [ { db => ['&','::=','fed.data.db'],
        src => ['::=','nlx.data'] } => '...' ] ],

    #######################################################################

            ] ], # depot-catalog #

            [ 'depot-data' => [ 'Database', {
                artists => [ '@', [ [ 'artist_name' ] => [
                    [ 'Michael Jackson' ],
                    [ 'Eminem'          ]
                ] ] ],
                cds => [ '@', [ [ 'cd_title','artist_name' ] => [
                    [ 'Thriller'               , 'Michael Jackson' ],
                    [ 'Bad'                    , 'Michael Jackson' ],
                    [ 'The Marshall Mathers LP', 'Eminem'          ]
                ] ] ],
                tracks => [ '@', [ [ 'track_title','cd_title' ] => [
                    [ 'Beat It'        , 'Thriller'                ],
                    [ 'Billie Jean'    , 'Thriller'                ],
                    [ 'Dirty Diana'    , 'Bad'                     ],
                    [ 'Smooth Criminal', 'Bad'                     ],
                    [ 'Leave Me Alone' , 'Bad'                     ],
                    [ 'Stan'           , 'The Marshall Mathers LP' ],
                    [ 'The Way I Am'   , 'The Marshall Mathers LP' ]
                ] ] ]
            } ] ] # depot-data #
        ]
    ]

HDMD_Perl5_STD - test_db

    [
        [ 'Muldis_D', 'http://muldis.com', '0.137.0', 'HDMD_Perl5_STD', {
            catalog_abstraction_level => 'rtn_inv_alt_syn',
            op_char_repertoire => 'basic'
        } ],

        [ 'depot',
            [ 'depot-catalog' => [
                [ 'stimulus-response-rule', 'bootstrap',
                    ['after-mount' => 'main'] ],

    #######################################################################

    [ 'procedure', 'main', [ {} => [
        # Connect to the_database in read-only mode. #
        # The "..." has likes of filename, server name, user, pass, etc. #
        [ 'iproc-imp-invo', 'create_depot_mount', { name => ['Name','db'],
            details => [ '@', 'OVLScaValExprNodeSet', '...' ] } ],

        # Fetch test data, in a transaction for read-consistency. #
        [ 'iproc-imp-invo', 'nlx.lib.get_records' ],

        # Disconnect the_database now that we're done with it. #
        [ 'iproc-imp-invo', 'drop_depot_mount', {name => ['Name','db']} ],
    ] ] ],

    #######################################################################

    [ 'transaction', 'get_records', [ {} => [
        [ 'iproc-imp-invo', 'nlx.lib.get_tracks_by_cd',
            { cd_title => 'Bad' } ],
        [ 'iproc-imp-invo', 'nlx.lib.get_tracks_by_artist',
            { artist_name => 'Michael Jackson' } ],

        [ 'iproc-imp-invo', 'nlx.lib.get_cd_by_track',
            { track_title => 'Stan' } ],
        [ 'iproc-imp-invo', 'nlx.lib.get_cds_by_artist',
            { artist_name => 'Michael Jackson' } ],

        [ 'iproc-imp-invo', 'nlx.lib.get_artist_by_track',
            { track_title => 'Dirty Diana' } ],
        [ 'iproc-imp-invo', 'nlx.lib.get_artist_by_cd',
            { cd_title => 'The Marshall Mathers LP' } ],
    ] ] ],

    #######################################################################

    [ 'procedure', 'disp_list', [ { h1 => 'Text', h2 => 'Text',
            list => 'array_of.Text' } => [
        [ 'var', 'eol', 'Text' ],
        [ 'iproc-imp-invo', 'end_of_line_Text', [ ['&',['d','eol']] ] ],
        [ 'var', 'msg', 'Text' ],
        [ 'atomic-stmt' => [
            [ 'op', ':=', [ ['d','msg'], [ 'op', '~', [
                ['d','h1'], '(', ['d','h2'], '):',
                ['d','eol'],
                [ 'func-invo', 'cat_with_sep', [ ['d','list'] ],
                    { 'sep' => ['d','eol'] } ],
                ['d','eol'], ['d','eol']
            ] ] ] ]
        ] ],
        [ 'iproc-imp-invo', 'write_Text', [ ['d','msg'] ] ],
    ] ] ],

    [ 'procedure', 'disp_item', [ { h1 => 'Text', h2 => 'Text',
        item => 'maybe_of.Text' } => '...' ] ],

    #######################################################################

    [ 'procedure', 'get_tracks_by_cd', [{ cd_title => 'Text' } => '...'] ],

    [ 'procedure', 'get_tracks_by_artist', [ { artist_name => 'Text' } => [
        [ 'var', 'track_titles', 'array_of.Text' ],
        [ 'iproc-imp-invo', 'fed.lib.db.get_tracks_by_artist',
            { track_titles => ['&',['d','track_titles']],
            artist_name => ['d','artist_name'] } ],
        [ 'iproc-imp-invo', 'nlx.lib.disp_list',
            { h1 => 'get_tracks_by_artist', h2 => ['d','artist_name'],
            list => ['d','track_titles'] } ],
    ] ] ],

    #######################################################################

    [ 'procedure', 'get_cd_by_track', [{track_title => 'Text'} => '...'] ],

    [ 'procedure', 'get_cds_by_artist', [{artist_name=>'Text'} => '...'] ],

    #######################################################################

    [ 'procedure', 'get_artist_by_track', [{track_title=>'Text'}=>'...'] ],

    [ 'procedure', 'get_artist_by_cd', [{ cd_title => 'Text' } => '...'] ],

    #######################################################################

            ] ] # depot-catalog #
        ]
    ]

EXPECTED OUTPUT ^

Each copy of the example should have identical output on STDOUT, which is:

    get_tracks_by_cd(Bad):
    Dirty Diana
    Leave Me Alone
    Smooth Criminal

    get_tracks_by_artist(Michael Jackson):
    Beat it
    Billie Jean
    Dirty Diana
    Leave Me Alone
    Smooth Criminal

    get_cd_by_track(Stan):
    The Marshall Mathers LP

    get_cds_by_artist(Michael Jackson):
    Bad
    Thriller

    get_artist_by_track(Dirty Diana):
    Michael Jackson

    get_artist_by_cd(The Marshall Mathers LP):
    Eminem

SEE ALSO ^

Go to Muldis::D::Manual for the majority of distribution-internal references.

Go to DBIx::Class::Manual::Example to see the original version of the "Simple CD database example" from which this document was originally derived/translated.

AUTHOR ^

The original document that this current document was translated from, DBIx::Class::Manual::Example, cites as its authors:

    sc_ from irc.perl.org#dbix-class
    Kieren Diment <kd@totaldatasolution.com>
    Nigel Metheringham <nigelm@cpan.org>

This current document was written/derived by:

    Darren Duncan <darren@DarrenDuncan.net>

LICENSE AND COPYRIGHT ^

This file is part of the Muldis D language and implementations manual.

Muldis D Manual is Copyright © 2008-2010, Muldis Data Systems, Inc.

See the LICENSE AND COPYRIGHT of Muldis::D::Manual for details.

TRADEMARK POLICY ^

The TRADEMARK POLICY in Muldis::D::Manual applies to this file too.

ACKNOWLEDGEMENTS ^

The ACKNOWLEDGEMENTS in Muldis::D::Manual apply to this file too.

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