//Storage.fsi
module Storage

[<Sealed>]
type Storage =
    new : unit -> Storage
    member AddActivity      : string * string -> unit
    member GetActivity      : string -> string option
    member RemoveActivity   : string -> unit
    member AddWorkflow      : string * string -> unit
    member GetWorkflow      : string -> string option
    member RemoveWorkflow   : string -> unit

//Storage.fs
module Storage

[<Sealed>]
type Storage() =
    let mutable Activities = Map.empty<string, string>
    let mutable Workflows  = Map.empty<string, string>

    member this.AddActivity (key,value) = Activities <- Activities.Add(key, value)
    member this.GetActivity key         = Activities.TryFind(key)
    member this.RemoveActivity key      = Activities <- Activities.Remove(key)
    member this.AddWorkflow (key,value) = Workflows  <- Workflows.Add(key, value)
    member this.GetWorkflow key         = Workflows.TryFind(key)
    member this.RemoveWorkflow key      = Workflows  <- Workflows.Remove(key)