One of many Sonos services in the F# type system

ZoneGroupTopology.fs

namespace Peelio.ZonePlayer.ZoneGroupTopology

open System
open System.Linq
open System.Xml.Linq
open Peelio

/// Union types for those state vars with a set of allowed values.
type A_ARG_TYPE_UpdateType = | All | Software
    with
        override __.ToString() = match __ with | All -> "All" | Software -> "Software"
        static member Parse(x:string) = match x with | "All" -> All | "Software" -> Software | _ -> failwith "Cannot parse value."

type A_ARG_TYPE_UnresponsiveDeviceActionType = | Remove | VerifyThenRemoveSystemwide
    with
        override __.ToString() = match __ with | Remove -> "Remove" | VerifyThenRemoveSystemwide -> "VerifyThenRemoveSystemwide"
        static member Parse(x:string) = match x with | "Remove" -> Remove | "VerifyThenRemoveSystemwide" -> VerifyThenRemoveSystemwide | _ -> failwith "Cannot parse value."

type A_ARG_TYPE_Origin = | Healthcheck | Server | User
    with
        override __.ToString() = match __ with | Healthcheck -> "Healthcheck" | Server -> "Server" | User -> "User"
        static member Parse(x:string) = match x with | "Healthcheck" -> Healthcheck | "Server" -> Server | "User" -> User | _ -> failwith "Cannot parse value."

/// Record type to hold all state values.
type ZoneGroupTopologyState = {
    AvailableSoftwareUpdate : String
    ZoneGroupState : String
    ThirdPartyMediaServersX : String
    AlarmRunSequence : String
    ZoneGroupName : String
    ZoneGroupID : String
    ZonePlayerUUIDsInGroup : String
    }

// Action response types (only for responses containing values).
type CheckForUpdateResponse = { UpdateItem : String }
type SubmitDiagnosticsResponse = { DiagnosticID : UInt32 }
type ZoneGroupAttributesResponse = { CurrentZoneGroupName : String; CurrentZoneGroupID : String; CurrentZonePlayerUUIDsInGroup : String }
type ZoneGroupStateResponse = { ZoneGroupState : String }

/// ZoneGroupTopology Service
type ZoneGroupTopologySvc private (device:Device, service:Service) =
    inherit Peelio.CpService(device, service)
    let (state:ZoneGroupTopologyState option ref) = ref None
    let onStateChange = Event<ZoneGroupTopologyState>()
    static let svcPath = DevicePart("ZonePlayer", 1, ServicePart("ZoneGroupTopology", 1))
    
    static member TryCreate(device) =
        match Upnp.tryFindService svcPath device with
        | Some(svc) -> Some(ZoneGroupTopologySvc(device, svc))
        | None -> None
    
    override __.OnUpnpEvent(eventXml:string) =
        let propMap = Upnp.eventPropStateMap eventXml
        match !state with
        | Some(s) -> ()//TODO update
        | None ->
            let newState =
                {
                    AvailableSoftwareUpdate = propMap.["AvailableSoftwareUpdate"]
                    ZoneGroupState = propMap.["ZoneGroupState"]
                    ThirdPartyMediaServersX = propMap.["ThirdPartyMediaServersX"]
                    AlarmRunSequence = propMap.["AlarmRunSequence"]
                    ZoneGroupName = propMap.["ZoneGroupName"]
                    ZoneGroupID = propMap.["ZoneGroupID"]
                    ZonePlayerUUIDsInGroup = propMap.["ZonePlayerUUIDsInGroup"]
                }
            state := Some newState
            onStateChange.Trigger(newState)
    
    
    [<CLIEvent>]
    member __.StateChanged = onStateChange.Publish
    
    member __.CheckForUpdate(updateType : A_ARG_TYPE_UpdateType, cachedOnly : Boolean, version : String) =
        async {
            let vals = ["UpdateType", updateType.ToString();"CachedOnly", cachedOnly.ToString();"Version", version.ToString();]
            let! resValMapOrEx = __.DoAction("CheckForUpdate", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2({ CheckForUpdateResponse.UpdateItem = valMap.Item("UpdateItem") })
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.BeginSoftwareUpdate(updateURL : String, flags : UInt32, extraOptions : String) =
        async {
            let vals = ["UpdateURL", updateURL.ToString();"Flags", flags.ToString();"ExtraOptions", extraOptions.ToString();]
            let! resValMapOrEx = __.DoAction("BeginSoftwareUpdate", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2(())
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.ReportUnresponsiveDevice(deviceUUID : String, desiredAction : A_ARG_TYPE_UnresponsiveDeviceActionType) =
        async {
            let vals = ["DeviceUUID", deviceUUID.ToString();"DesiredAction", desiredAction.ToString();]
            let! resValMapOrEx = __.DoAction("ReportUnresponsiveDevice", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2(())
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.ReportAlarmStartedRunning() =
        async {
            let vals = []
            let! resValMapOrEx = __.DoAction("ReportAlarmStartedRunning", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2(())
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.SubmitDiagnostics(includeControllers : Boolean, t : A_ARG_TYPE_Origin) =
        async {
            let vals = ["IncludeControllers", includeControllers.ToString();"Type", t.ToString();]
            let! resValMapOrEx = __.DoAction("SubmitDiagnostics", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2({ SubmitDiagnosticsResponse.DiagnosticID = Convert.ChangeType(valMap.Item("DiagnosticID"), typeof<UInt32>) :?> UInt32 })
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.RegisterMobileDevice(mobileDeviceName : String, mobileDeviceUDN : String, mobileIPAndPort : String) =
        async {
            let vals = ["MobileDeviceName", mobileDeviceName.ToString();"MobileDeviceUDN", mobileDeviceUDN.ToString();"MobileIPAndPort", mobileIPAndPort.ToString();]
            let! resValMapOrEx = __.DoAction("RegisterMobileDevice", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2(())
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.GetZoneGroupAttributes() =
        async {
            let vals = []
            let! resValMapOrEx = __.DoAction("GetZoneGroupAttributes", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2({ ZoneGroupAttributesResponse.CurrentZoneGroupName = valMap.Item("CurrentZoneGroupName"); CurrentZoneGroupID = valMap.Item("CurrentZoneGroupID"); CurrentZonePlayerUUIDsInGroup = valMap.Item("CurrentZonePlayerUUIDsInGroup") })
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }
    member __.GetZoneGroupState() =
        async {
            let vals = []
            let! resValMapOrEx = __.DoAction("GetZoneGroupState", vals)
            match resValMapOrEx with
            | Choice1Of2(valMap) -> return Choice1Of2({ ZoneGroupStateResponse.ZoneGroupState = valMap.Item("ZoneGroupState") })
            | Choice2Of2(ex) -> return Choice2Of2(ex)
        }

You'll note that the properties for this service are quite stringy. Wont be like that for long.