Inventory of the Microsoft.ML public types: what to rename, move, hide there.

[sfilipi]

This is the list of the types in the Microsoft.ML namespace, as seen from the docs site. Taking a first pass at what doesn't need to be there, what needs to be hidden, and what needs to be moved to a different namespace.

Microsoft.ML namespace type	Rename/Move/Hide
BinaryClassificationCatalog
BinaryClassificationCatalog.BinaryClassificationTrainers
BinaryClassificationMetricsStatistics
BinaryLoaderSaverCatalog
CategoricalCatalog
ChannelMessage	move to Microsoft.ML.Data
ChannelMessageKind	move to Microsoft.ML.Data
ClusteringCatalog
ClusteringCatalog.ClusteringTrainers
ComponentCatalog	move to Microsoft.ML.Core
ConversionsCatalog
ConversionsExtensionsCatalog
CustomMappingCatalog
DataOperationsCatalog
DataReaderExtensions
DebuggerExtensions
ExplainabilityCatalog
ExpLoss	move to Microsoft.ML.Trainers.Loss
ExpLoss.Arguments	move to Microsoft.ML.Trainers.Loss
ExtensionsCatalog
FactorizationMachineExtensions
FeatureSelectionCatalog
HalLearnersCatalog
HingeLoss	move to Microsoft.ML.Trainers.Loss
HingeLoss.Arguments	move to Microsoft.ML.Trainers.Loss
IChannel	move to Microsoft.ML.Data
IChannelProvider	move to Microsoft.ML.Data
IClassificationLoss	move to Microsoft.ML.Trainers.Loss
IComponentFactory	move to Microsoft.ML.Data
IComponentFactory	move to Microsoft.ML.Data
IComponentFactory<TArg1,TComponent>	move to Microsoft.ML.Data
IComponentFactory<TArg1,TArg2,TComponent>	move to Microsoft.ML.Data
IComponentFactory<TArg1,TArg2,TArg3,TComponent>	move to Microsoft.ML.Data
IExceptionContext	move to Microsoft.ML.Core
IFileHandle	move to Microsoft.ML.Data
IHost	move to Microsoft.ML.Data
IHostEnvironment	move to Microsoft.ML.Data
ILossFunction<TOutput,TLabel>	move to Microsoft.ML.Trainers.Loss
ImageEstimatorsCatalog
IParameterValue	move to Microsoft.ML.Sweeper
IParameterValue	move to Microsoft.ML.Sweeper
IPipe	move to Microsoft.ML.Data
IPredictionTransformer
IPredictor
IPredictorProducing
IProgressChannel	move to Microsoft.ML.Data
IProgressChannelProvider	move to Microsoft.ML.Data
IProgressEntry	move to Microsoft.ML.Data
IRegressionLoss	move to Microsoft.ML.Trainers.Loss
IRunResult	move to Microsoft.ML.Sweeper
IRunResult	move to Microsoft.ML.Sweeper
IScalarOutputLoss	move to Microsoft.ML.Trainers.Loss
ISingleFeaturePredictionTransformer
ISupportClassificationLossFactory	move to Microsoft.ML.Trainers.Loss
ISupportRegressionLossFactory	move to Microsoft.ML.Trainers.Loss
ISupportSdcaClassificationLoss	move to Microsoft.ML.Trainers.Loss
ISupportSdcaClassificationLossFactory	move to Microsoft.ML.Trainers.Loss
ISupportSdcaRegressionLossFactory	move to Microsoft.ML.Trainers.Loss
ISweeper	move to Microsoft.ML.Sweeper
ISweepResultEvaluator	move to Microsoft.ML.Sweeper
IValueGenerator	move to Microsoft.ML.Sweeper
KMeansClusteringExtensions
LearningPipelineExtensions
LightGbmExtensions
LoggingEventArgs
LogLoss	move to Microsoft.ML.Trainers.Loss
LogLossFactory	move to Microsoft.ML.Trainers.Loss
MessageSensitivity	move to Microsoft.ML.Data
MetricsStatisticsBase	move to Microsoft.ML.Data
MetricStatistics	move to Microsoft.ML.Data
MLContext
ModelOperationsCatalog
ModelOperationsCatalog.ExplainabilityTransforms
ModelOperationsCatalog.SubCatalogBase
MulticlassClassificationCatalog
MulticlassClassificationCatalog.MulticlassClassificationTrainers
MultiClassClassifierMetricsStatistics	move to Microsoft.ML.Data
NormalizerCatalog
OnnxCatalog
OnnxExportExtensions
ParameterSet	move to Microsoft.ML.Sweeper
PcaCatalog
PermutationFeatureImportanceExtensions	move to Microsoft.ML.Data
PoissonLoss	move to Microsoft.ML.Trainers.Loss
PoissonLossFactory	move to Microsoft.ML.Trainers.Loss
PredictionEngine<TSrc,TDst>
PredictionEngineBase<TSrc,TDst>
PredictionEngineExtensions
PredictionKind
ProgressHeader	move to Microsoft.ML.Data
ProjectionCatalog
QuantileStatistics	move to Microsoft.ML.Data
RankerMetricsStatistics	move to Microsoft.ML.Data
RankingCatalog
RankingCatalog.RankingTrainers
RecommendationCatalog
RecommendationCatalog.RecommendationTrainers
RecommenderCatalog
RegressionCatalog
RegressionCatalog.RegressionTrainers
RegressionMetricsStatistics	move to Microsoft.ML.Data
RunMetric	move to Microsoft.ML.Sweeper
RunResult	move to Microsoft.ML.Sweeper
SignatureClassificationLoss	move to Microsoft.ML.Trainers.Loss
SignatureRegressionLoss	move to Microsoft.ML.Trainers.Loss
SignatureSuggestedSweepsParser	move to Microsoft.ML.Sweeper
SignatureSweeper	move to Microsoft.ML.Sweeper
SignatureSweepResultEvaluator	move to Microsoft.ML.Sweeper
SimpleFileHandle	move to Microsoft.ML.Data
SmoothedHingeLoss	move to Microsoft.ML.Trainers.Loss
SmoothedHingeLoss.Arguments	move to Microsoft.ML.Trainers.Loss
SquaredLoss	move to Microsoft.ML.Trainers.Loss
SquaredLossFactory	move to Microsoft.ML.Trainers.Loss
StandardLearnersCatalog
TensorflowCatalog
TextCatalog
TextLoaderSaverCatalog
TrainCatalogBase
TrainCatalogBase.CatalogInstantiatorBase	hide
TrainerInfo
TransformExtensionsCatalog
TransformsCatalog
TransformsCatalog.CategoricalTransforms
TransformsCatalog.ConversionTransforms
TransformsCatalog.FeatureSelectionTransforms
TransformsCatalog.ProjectionTransforms
TransformsCatalog.SubCatalogBase
TransformsCatalog.TextTransforms
TreeExtensions
TweedieLoss	move to Microsoft.ML.Trainers.Loss
TweedieLoss.Arguments	move to Microsoft.ML.Trainers.Loss

cc @yaeldekel @TomFinley @glebuk see if any of my suggestions need to change.
For the cases marked with move, where should they live?

[TomFinley]

If I read through your list, I notice two main themes here among your "moves:" losses, and things relating to IHostEnvironment.

Losses seem most relevant to trainers (e.g., they are often moved there), so if not in ML.NET they should live somewhere there, I'd expect? Maybe Microsoft.ML.Trainers, since the concept of loss is so general? But they're also useful in evaluation -- we might want to consider the possibility that loss is so fundamental a concept that it may even deserve its own special namespace, though I hardly insist on this. Another note about losses: Note that ISupportSdcaClassificationLossFactory and suchlike ought to be hidden, and the public API should not expose them. See #1973.

You did not mention moving IHost. Anything related to IHostEnvironment (including ProgressHeader, ChannelMessage, ComponentCatalog, and other such things) should live in some special namespace that users won't be bothered with. (I am somewhat indifferent as to choice of name, just, something user's won't use.) This would include I suppose also any other types that have to be public for "reasons" but that are nonetheless only useful to component authors. That definitely shouldn't be in people's faces.

[TomFinley]

Also why do we have the sweeper DLL part of Microsoft.ML nuget? 😄 That's not right.

[TomFinley]

Also also: this is necessarily a breaking change to API, so why is it filed under documentation and not under project 13 and API? I hope you don't mind, going to add those labels, since those strike me as more appropriate.

[TomFinley]

One thing I noticed is that IHostEnvironment and its friends are sitll in the main Microsoft.ML. While MLContext must be in Microsoft.ML, IHostEnvironment should be somewhere else, somewhere where user non-component authoring code won't be too likely to run into it. I'm somewhat indifferent as to where.

[eerhardt]

Also why do we have the sweeper DLL part of Microsoft.ML nuget?

It is no longer after #2690.

[TomFinley]

I might prefer that IHostEnvironment and its friends not be in any API that a typical user would stumble upon. This seems to disqualify not only Microsoft.ML but Microsoft.ML.Data. @eerhardt jokingly suggested Microsoft.ML.Runtime, but might we want to make his joke real? That's not such a problematic namespace really, considering that it deals with component authorship. (I don't insist on that name, I just think it should be a namespace that only component authors would tend to be on.)

[TomFinley]

Otherwise at first glance things look pretty good. Some of these will become internalized and hidden w.r.t. #1973 and related downstream work being done by @ganik.

[sfilipi]

Closed with #2885