collectionAPI.h

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//
// Copyright 2016 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef USD_GENERATED_COLLECTIONAPI_H
#define USD_GENERATED_COLLECTIONAPI_H

/// \file usd/collectionAPI.h

#include "pxr/pxr.h"
#include "pxr/usd/usd/api.h"
#include "pxr/usd/usd/apiSchemaBase.h"
#include "pxr/usd/usd/prim.h"
#include "pxr/usd/usd/stage.h"
#include "pxr/usd/usd/tokens.h"

#include "pxr/usd/usd/collectionMembershipQuery.h"
#include "pxr/usd/usd/primFlags.h"
#include "pxr/usd/usd/tokens.h"
#include "pxr/usd/sdf/pathExpression.h"


#include "pxr/base/vt/value.h"

#include "pxr/base/gf/vec3d.h"
#include "pxr/base/gf/vec3f.h"
#include "pxr/base/gf/matrix4d.h"

#include "pxr/base/tf/token.h"
#include "pxr/base/tf/type.h"

PXR_NAMESPACE_OPEN_SCOPE

class SdfAssetPath;

// -------------------------------------------------------------------------- //
// COLLECTIONAPI                                                              //
// -------------------------------------------------------------------------- //

/// \class UsdCollectionAPI
///
/// A general purpose API schema used to describe a collection of prims
/// and properties within a scene. This API schema can be applied to a prim
/// multiple times with different instance names to define several collections
/// on a single prim.
/// 
/// A collection's membership is specified one of two ways. The first way uses
/// the built-in relationships `includes` and `excludes`, and the attribute
/// `includeRoot` to determine membership. The second way is termed a
/// pattern-based collection, and uses the built-in attribute
/// `membershipExpression` to determine membership. Here we will refer to
/// collections using `includes`, `excludes` and `includeRoot` as being in
/// *relationship-mode* and those using the `membershipExpression` as being in
/// *expression-mode*.
/// 
/// The `mode` attribute controls which mode the collection uses.  When set to
/// `relationship` the collection is explicitly in *relationship-mode*, and when
/// set to `expression` it is explicitly in *expression-mode*.  Properties
/// belonging to the non-selected mode are ignored.  When `mode` is `automatic`
/// (the default), the mode is inferred from the collection's authored
/// properties: the collection is in *relationship-mode* when either or both of
/// its `includes` and `excludes` relationships have valid targets, or the
/// `includeRoot` attribute is set to `true`; otherwise it is in
/// *expression-mode* and the `membershipExpression` attribute applies.
/// 
/// In *relationship-mode* the `includes` and `excludes` relationships specify
/// the collection members as a set of paths to include and a set of paths to
/// exclude.  Whether or not the descendants of an included path belong to a
/// collection is decided by its expansion rule (see below).  If the collection
/// excludes paths that are not descendent to included paths, the collection
/// implicitly includes the root path `</>`.  If such a collection also
/// includes paths that are not descendent to the excluded paths, it is
/// considered invalid since the intent is ambiguous.
/// 
/// In *expression-mode*, the pattern-based `membershipExpression` attribute is
/// used with the `expansionRule` attribute to determine collection membership.
/// See the detailed descriptions of the built-in properties below for more
/// details.
/// 
/// \section usd_collectionapi_properties Collection API Properties
/// 
/// The built-in properties for this schema are in the `collection:instanceName`
/// namespace, where `instanceName` is the user-provided applied API schema
/// instance name.
/// 
/// <ul>
/// <li>`uniform token collection:instanceName:expansionRule` - in
/// *relationship-mode*, specifies how to expand the `includes` and `excludes`
/// relationship targets to determine the collection's members.  In
/// *expression-mode*, specifies how matching scene objects against the
/// `membershipExpression` proceeds.  Possible values include:
/// <ul>
/// <li>`expandPrims` - in *relationship-mode*, all the prims descendent
/// to the `includes` relationship targets (and not descendent to `excludes`
/// relationship targets) belong to the collection.  Any `includes`-targeted
/// property paths also belong to the collection. This is the default
/// behavior. In *expression-mode*, the functions
/// UsdComputeIncludedObjectsFromCollection() and
/// UsdComputeIncludedPathsFromCollection() only test prims against the
/// `membershipExpression` to determine membership.
/// </li>
/// <li>`expandPrimsAndProperties` - like `expandPrims`, but in
/// *relationship-mode*, all properties on all included prims also belong to
/// the collection. In *expression-mode*, the functions
/// UsdComputeIncludedObjectsFromCollection() and
/// UsdComputeIncludedPathsFromCollection() test both prims and
/// properties against the `membershipExpression` to determine membership.
/// </li>
/// <li>`explicitOnly` - in *relationship-mode*, only paths in the
/// `includes` relationship targets and not those in the `excludes`
/// relationship targets belong to the collection. Does not apply to
/// *expression-mode*. If set in *expression-mode*, the functions
/// UsdComputeIncludedObjectsFromCollection() and
/// UsdComputeIncludedPathsFromCollection() return no results.
/// </li>
/// </ul>
/// </li>
/// 
/// <li>`bool collection:instanceName:includeRoot` - boolean attribute
/// indicating whether the pseudo-root path `</>` should be counted as one
/// of the included target paths in *relationship-mode*. This separate attribute
/// is required because relationships cannot directly target the root. When
/// `expansionRule` is `explicitOnly`, this attribute is ignored. The fallback
/// value is false. When set to `true`, this collection is in
/// *relationship-mode*. This attribute is ignored in *expression-mode*.  </li>
/// 
/// <li>`rel collection:instanceName:includes` - in *relationship-mode*,
/// specifies a list of targets that are included in the collection. This can
/// target prims or properties directly. A collection can insert the rules of
/// another collection by making its `includes` relationship target the
/// `collection:otherInstanceName` property from the collection to be included
/// (see UsdCollectionAPI::GetCollectionAttr).  Note that including another
/// collection does not guarantee the contents of that collection will be in the
/// final collection; instead, the rules are merged.  This means, for example,
/// an exclude entry may exclude a portion of the included collection.  When a
/// collection includes one or more collections, the order in which targets are
/// added to the includes relationship may become significant, if there are
/// conflicting opinions about the same path. Targets that are added later are
/// considered to be stronger than earlier targets for the same path.  This
/// relationship is ignored in *expression-mode*.</li>
/// 
/// <li>`rel collection:instanceName:excludes` - in *relationship-mode*,
/// specifies a list of targets that are excluded below the <b>included</b>
/// paths in this collection. This can target prims or properties directly, but
/// <b>cannot target another collection</b>. This is to keep the membership
/// determining logic simple, efficient and easier to reason about. Finally, it
/// is invalid for a collection to exclude paths that are not included in
/// it. The presence of such "orphaned" excluded paths will not affect the set
/// of paths included in the collection, but may affect the performance of
/// querying membership of a path in the collection (see
/// UsdCollectionMembershipQuery::IsPathIncluded) or of enumerating the
/// objects belonging to the collection (see
/// UsdCollectionAPI::ComputeIncludedObjects).  This relationship is ignored in
/// *expression-mode*.</li>
/// 
/// <li>`uniform opaque collection:instanceName` - opaque
/// attribute (meaning it can never have a value) that represents the collection
/// for the purpose of allowing another collection to include it in
/// *relationship-mode*. When this property is targeted by another collection's
/// `includes` relationship, the rules of this collection will be inserted
/// into the rules of the collection that includes it.</li>
/// 
/// <li>`uniform pathExpression collection:instanceName:membershipExpression` -
/// in *expression-mode*, defines the SdfPathExpression used to test
/// objects for collection membership.</li>
/// 
/// </ul>
/// 
/// \subsection usd_collectionapi_implicit_inclusion Implicit Inclusion
/// 
/// In some scenarios it is useful to express a collection that includes
/// everything except certain paths.  To support this, a *relationship-mode*
/// collection that has an exclude that is not descendent to any include will
/// include the root path `</>`.
/// 
/// \section usd_collectionapi_creating_cpp Creating Collections in C++
/// 
/// \snippet examples_usd.cpp ApplyCollections
/// 
///
/// For any described attribute \em Fallback \em Value or \em Allowed \em Values below
/// that are text/tokens, the actual token is published and defined in \ref UsdTokens.
/// So to set an attribute to the value "rightHanded", use UsdTokens->rightHanded
/// as the value.
///
class UsdCollectionAPI : public UsdAPISchemaBase
{
public:
    /// Compile time constant representing what kind of schema this class is.
    ///
    /// \sa UsdSchemaKind
    static const UsdSchemaKind schemaKind = UsdSchemaKind::MultipleApplyAPI;

    /// Construct a UsdCollectionAPI on UsdPrim \p prim with
    /// name \p name . Equivalent to
    /// UsdCollectionAPI::Get(
    ///    prim.GetStage(),
    ///    prim.GetPath().AppendProperty(
    ///        "collection:name"));
    ///
    /// for a \em valid \p prim, but will not immediately throw an error for
    /// an invalid \p prim
    explicit UsdCollectionAPI(
        const UsdPrim& prim=UsdPrim(), const TfToken &name=TfToken())
        : UsdAPISchemaBase(prim, /*instanceName*/ name)
    { }

    /// Construct a UsdCollectionAPI on the prim held by \p schemaObj with
    /// name \p name.  Should be preferred over
    /// UsdCollectionAPI(schemaObj.GetPrim(), name), as it preserves
    /// SchemaBase state.
    explicit UsdCollectionAPI(
        const UsdSchemaBase& schemaObj, const TfToken &name)
        : UsdAPISchemaBase(schemaObj, /*instanceName*/ name)
    { }

    /// Destructor.
    USD_API
    virtual ~UsdCollectionAPI();

    /// Return a vector of names of all pre-declared attributes for this schema
    /// class and all its ancestor classes.  Does not include attributes that
    /// may be authored by custom/extended methods of the schemas involved.
    USD_API
    static const TfTokenVector &
    GetSchemaAttributeNames(bool includeInherited=true);

    /// Return a vector of names of all pre-declared attributes for this schema
    /// class and all its ancestor classes for a given instance name.  Does not
    /// include attributes that may be authored by custom/extended methods of
    /// the schemas involved. The names returned will have the proper namespace
    /// prefix.
    USD_API
    static TfTokenVector
    GetSchemaAttributeNames(bool includeInherited, const TfToken &instanceName);

    /// Returns the name of this multiple-apply schema instance
    TfToken GetName() const {
        return _GetInstanceName();
    }

    /// Return a UsdCollectionAPI holding the prim adhering to this
    /// schema at \p path on \p stage.  If no prim exists at \p path on
    /// \p stage, or if the prim at that path does not adhere to this schema,
    /// return an invalid schema object.  \p path must be of the format
    /// <path>.collection:name .
    ///
    /// This is shorthand for the following:
    ///
    /// \code
    /// TfToken name = SdfPath::StripNamespace(path.GetToken());
    /// UsdCollectionAPI(
    ///     stage->GetPrimAtPath(path.GetPrimPath()), name);
    /// \endcode
    ///
    USD_API
    static UsdCollectionAPI
    Get(const UsdStagePtr &stage, const SdfPath &path);

    /// Return a UsdCollectionAPI with name \p name holding the
    /// prim \p prim. Shorthand for UsdCollectionAPI(prim, name);
    USD_API
    static UsdCollectionAPI
    Get(const UsdPrim &prim, const TfToken &name);

    /// Return a vector of all named instances of UsdCollectionAPI on the 
    /// given \p prim.
    USD_API
    static std::vector<UsdCollectionAPI>
    GetAll(const UsdPrim &prim);

    /// Checks if the given name \p baseName is the base name of a property
    /// of CollectionAPI.
    USD_API
    static bool
    IsSchemaPropertyBaseName(const TfToken &baseName);

    /// Checks if the given path \p path is of an API schema of type
    /// CollectionAPI. If so, it stores the instance name of
    /// the schema in \p name and returns true. Otherwise, it returns false.
    USD_API
    static bool
    IsCollectionAPIPath(const SdfPath &path, TfToken *name);

    /// Returns true if this <b>multiple-apply</b> API schema can be applied,
    /// with the given instance name, \p name, to the given \p prim. If this 
    /// schema can not be a applied the prim, this returns false and, if 
    /// provided, populates \p whyNot with the reason it can not be applied.
    /// 
    /// Note that if CanApply returns false, that does not necessarily imply
    /// that calling Apply will fail. Callers are expected to call CanApply
    /// before calling Apply if they want to ensure that it is valid to 
    /// apply a schema.
    /// 
    /// \sa UsdPrim::GetAppliedSchemas()
    /// \sa UsdPrim::HasAPI()
    /// \sa UsdPrim::CanApplyAPI()
    /// \sa UsdPrim::ApplyAPI()
    /// \sa UsdPrim::RemoveAPI()
    ///
    USD_API
    static bool 
    CanApply(const UsdPrim &prim, const TfToken &name, 
             std::string *whyNot=nullptr);

    /// Applies this <b>multiple-apply</b> API schema to the given \p prim 
    /// along with the given instance name, \p name. 
    /// 
    /// This information is stored by adding "CollectionAPI:<i>name</i>" 
    /// to the token-valued, listOp metadata \em apiSchemas on the prim.
    /// For example, if \p name is 'instance1', the token 
    /// 'CollectionAPI:instance1' is added to 'apiSchemas'.
    /// 
    /// \return A valid UsdCollectionAPI object is returned upon success. 
    /// An invalid (or empty) UsdCollectionAPI object is returned upon 
    /// failure. See \ref UsdPrim::ApplyAPI() for 
    /// conditions resulting in failure. 
    /// 
    /// \sa UsdPrim::GetAppliedSchemas()
    /// \sa UsdPrim::HasAPI()
    /// \sa UsdPrim::CanApplyAPI()
    /// \sa UsdPrim::ApplyAPI()
    /// \sa UsdPrim::RemoveAPI()
    ///
    USD_API
    static UsdCollectionAPI 
    Apply(const UsdPrim &prim, const TfToken &name);

protected:
    /// Returns the kind of schema this class belongs to.
    ///
    /// \sa UsdSchemaKind
    USD_API
    UsdSchemaKind _GetSchemaKind() const override;

private:
    // needs to invoke _GetStaticTfType.
    friend class UsdSchemaRegistry;
    USD_API
    static const TfType &_GetStaticTfType();

    static bool _IsTypedSchema();

    // override SchemaBase virtuals.
    USD_API
    const TfType &_GetTfType() const override;

public:
    // --------------------------------------------------------------------- //
    // EXPANSIONRULE 
    // --------------------------------------------------------------------- //
    /// Specifies how the paths that are included in
    /// the collection must be expanded to determine its members.
    ///
    /// | ||
    /// | -- | -- |
    /// | Declaration | `uniform token expansionRule = "expandPrims"` |
    /// | C++ Type | TfToken |
    /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Token |
    /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
    /// | \ref UsdTokens "Allowed Values" | explicitOnly, expandPrims, expandPrimsAndProperties |
    USD_API
    UsdAttribute GetExpansionRuleAttr() const;

    /// See GetExpansionRuleAttr(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
    /// If specified, author \p defaultValue as the attribute's default,
    /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
    /// the default for \p writeSparsely is \c false.
    USD_API
    UsdAttribute CreateExpansionRuleAttr(VtValue const &defaultValue = VtValue(), bool writeSparsely=false) const;

public:
    // --------------------------------------------------------------------- //
    // INCLUDEROOT 
    // --------------------------------------------------------------------- //
    /// Boolean attribute indicating whether the pseudo-root
    /// path `</>` should be counted as one of the included target
    /// paths.  The fallback is false.  This separate attribute is
    /// required because relationships cannot directly target the root.
    ///
    /// | ||
    /// | -- | -- |
    /// | Declaration | `uniform bool includeRoot` |
    /// | C++ Type | bool |
    /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Bool |
    /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
    USD_API
    UsdAttribute GetIncludeRootAttr() const;

    /// See GetIncludeRootAttr(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
    /// If specified, author \p defaultValue as the attribute's default,
    /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
    /// the default for \p writeSparsely is \c false.
    USD_API
    UsdAttribute CreateIncludeRootAttr(VtValue const &defaultValue = VtValue(), bool writeSparsely=false) const;

public:
    // --------------------------------------------------------------------- //
    // MEMBERSHIPEXPRESSION 
    // --------------------------------------------------------------------- //
    /// Specifies a path expression that determines membership in this
    /// collection.
    ///
    /// | ||
    /// | -- | -- |
    /// | Declaration | `uniform pathExpression membershipExpression` |
    /// | C++ Type | SdfPathExpression |
    /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->PathExpression |
    /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
    USD_API
    UsdAttribute GetMembershipExpressionAttr() const;

    /// See GetMembershipExpressionAttr(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
    /// If specified, author \p defaultValue as the attribute's default,
    /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
    /// the default for \p writeSparsely is \c false.
    USD_API
    UsdAttribute CreateMembershipExpressionAttr(VtValue const &defaultValue = VtValue(), bool writeSparsely=false) const;

public:
    // --------------------------------------------------------------------- //
    // MODE 
    // --------------------------------------------------------------------- //
    /// Specifies which mode the collection uses to determine
    /// membership: `automatic`, `relationship`, or `expression`.
    /// <ul>
    /// <li>`automatic` - the collection's mode is inferred from its authored
    /// properties.  If either or both of the `includes` and `excludes`
    /// relationships have valid targets, or the `includeRoot` attribute is set
    /// to `true`, the collection is in *relationship-mode* and the
    /// `membershipExpression` attribute is ignored.  Otherwise, the collection
    /// is in *expression-mode* and the `membershipExpression` attribute
    /// applies.  This is the default behavior and is backward compatible with
    /// collections that predate this attribute.</li>
    /// <li>`relationship` - the collection is explicitly in
    /// *relationship-mode*.  The `includes`, `excludes`, and `includeRoot`
    /// attributes determine membership, and `membershipExpression` is
    /// ignored.</li>
    /// <li>`expression` - the collection is explicitly in *expression-mode*.
    /// The `membershipExpression` attribute determines membership, and
    /// `includes`, `excludes`, and `includeRoot` are ignored.</li>
    /// </ul>
    /// The fallback value is `automatic`.
    ///
    /// | ||
    /// | -- | -- |
    /// | Declaration | `uniform token mode = "automatic"` |
    /// | C++ Type | TfToken |
    /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Token |
    /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
    /// | \ref UsdTokens "Allowed Values" | automatic, relationship, expression |
    USD_API
    UsdAttribute GetModeAttr() const;

    /// See GetModeAttr(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
    /// If specified, author \p defaultValue as the attribute's default,
    /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
    /// the default for \p writeSparsely is \c false.
    USD_API
    UsdAttribute CreateModeAttr(VtValue const &defaultValue = VtValue(), bool writeSparsely=false) const;

public:
    // --------------------------------------------------------------------- //
    // COLLECTION 
    // --------------------------------------------------------------------- //
    /// This property represents the collection for the purpose of 
    /// allowing another collection to include it. When this property is 
    /// targeted by another collection's <i>includes</i> relationship, the rules
    /// of this collection will be inserted into the rules of the collection
    /// that includes it.
    /// 
    ///
    /// | ||
    /// | -- | -- |
    /// | Declaration | `uniform opaque __INSTANCE_NAME__` |
    /// | C++ Type | SdfOpaqueValue |
    /// | \ref Usd_Datatypes "Usd Type" | SdfValueTypeNames->Opaque |
    /// | \ref SdfVariability "Variability" | SdfVariabilityUniform |
    USD_API
    UsdAttribute GetCollectionAttr() const;

    /// See GetCollectionAttr(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create.
    /// If specified, author \p defaultValue as the attribute's default,
    /// sparsely (when it makes sense to do so) if \p writeSparsely is \c true -
    /// the default for \p writeSparsely is \c false.
    USD_API
    UsdAttribute CreateCollectionAttr(VtValue const &defaultValue = VtValue(), bool writeSparsely=false) const;

public:
    // --------------------------------------------------------------------- //
    // INCLUDES 
    // --------------------------------------------------------------------- //
    /// Specifies a list of targets that are included in the collection.
    /// This can target prims or properties directly. A collection can insert
    /// the rules of another collection by making its <i>includes</i>
    /// relationship target the <b>collection:{collectionName}</b> property on
    /// the owning prim of the collection to be included
    ///
    USD_API
    UsdRelationship GetIncludesRel() const;

    /// See GetIncludesRel(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create
    USD_API
    UsdRelationship CreateIncludesRel() const;

public:
    // --------------------------------------------------------------------- //
    // EXCLUDES 
    // --------------------------------------------------------------------- //
    /// Specifies a list of targets that are excluded below
    /// the included paths in this collection. This can target prims or
    /// properties directly, but cannot target another collection. This is to
    /// keep the membership determining logic simple, efficient and easier to
    /// reason about. Finally, it is invalid for a collection to exclude
    /// paths that are not included in it. The presence of such "orphaned"
    /// excluded paths will not affect the set of paths included in the
    /// collection, but may affect the performance of querying membership of 
    /// a path in the collection (see
    /// UsdCollectionAPI::MembershipQuery::IsPathIncluded) 
    /// or of enumerating the objects belonging to the collection (see 
    /// UsdCollectionAPI::GetIncludedObjects).
    ///
    USD_API
    UsdRelationship GetExcludesRel() const;

    /// See GetExcludesRel(), and also 
    /// \ref Usd_Create_Or_Get_Property for when to use Get vs Create
    USD_API
    UsdRelationship CreateExcludesRel() const;

public:
    // ===================================================================== //
    // Feel free to add custom code below this line, it will be preserved by 
    // the code generator. 
    //
    // Just remember to: 
    //  - Close the class declaration with }; 
    //  - Close the namespace with PXR_NAMESPACE_CLOSE_SCOPE
    //  - Close the include guard with #endif
    // ===================================================================== //
    // --(BEGIN CUSTOM CODE)--

public:
    /// Returns the collection represented by the given collection path, 
    /// \p collectionPath on the given USD stage.
    USD_API
    static UsdCollectionAPI GetCollection(const UsdStagePtr &stage, 
                                          const SdfPath &collectionPath);

    /// Returns the schema object representing a collection named \p name on 
    /// the given \p prim.
    USD_API
    static UsdCollectionAPI GetCollection(const UsdPrim &prim, 
                                          const TfToken &name);

    /// Returns all the named collections on the given USD prim.
    /// \deprecated Use GetAll(prim) instead.
    USD_API
    static std::vector<UsdCollectionAPI> GetAllCollections(const UsdPrim &prim);

    /// Returns the canonical path that represents this collection. 
    /// This points to the property named "collection:{collectionName}" on the 
    /// prim defining the collection. This is the path to be used to "include" 
    /// this collection in another collection.
    ///
    /// \sa GetCollectionAttr()
    USD_API
    SdfPath GetCollectionPath() const;

    /// Returns the canonical path to the collection named, \p name on the given
    /// prim, \p prim.
    /// 
    /// \sa GetCollectionPath()
    USD_API
    static SdfPath GetNamedCollectionPath(
        const UsdPrim &prim, 
        const TfToken &collectionName);

    /// Obtain a complete SdfPathExpression from this collection's
    /// membershipExpression.  First, UsdAttribute::Get() the value of
    /// GetMembershipExpressionAttr(), then resolve any contained references.
    /// Replace any remaining "weaker" references (%_) with
    /// SdfPathExpression::Nothing().  Replace other references by recursively
    /// resolving the expressions from the collections on the referenced prims.
    /// If no such prims or no such collections exist, replace those references
    /// with SdfPathExpression::Nothing() as well.
    USD_API
    SdfPathExpression ResolveCompleteMembershipExpression() const;
    
    // Convenient alias for UsdCollectionMembershipQuery object
    using MembershipQuery = UsdCollectionMembershipQuery;

    /// Computes and returns a UsdCollectionMembershipQuery object which can
    /// be used to query inclusion or exclusion of paths in the collection.
    USD_API
    UsdCollectionMembershipQuery ComputeMembershipQuery() const;

    /// Populates the UsdCollectionMembershipQuery object with data from this
    /// collection, so it can be used to query inclusion or exclusion of paths.
    USD_API
    void ComputeMembershipQuery(UsdCollectionMembershipQuery *query) const;

    /// Return true if the collection cannot possibly include anything.
    ///
    /// For collections in relationships-mode, this is the case if the includes
    /// relationship has no target paths, and the includeRoot attribute is
    /// false.
    ///
    /// For collections in expression-mode, this is the case if the
    /// membershipExpression attribute has either no opinion or if it is
    /// SdfPathExpression::Nothing().
    ///
    /// Note that there may be cases where the collection includes no objects
    /// despite HasNoIncludedPaths() returning false.  For example, if the
    /// included objects are unloaded, or if the included objects are also
    /// excluded, or if an authored non-empty membershipExpression happens not
    /// to match any objects on the stage.
    USD_API
    bool HasNoIncludedPaths() const;

    /// Return true if this collection is *relationships-mode*.  That is, if it
    /// uses the `includes` and `excludes` relationships to determine membership
    /// and not the `membershipExpression` attribute.  This is the case when the
    /// `mode` attribute is set to `relationship`, or when the mode attribute is
    /// set to `automatic` and either or both of its `includes` and `excludes`
    /// relationships have valid targets, or the `includeRoot` attribute is set
    /// `true`.  This is equivalent to `!IsInExpressionMode()`.
    USD_API
    bool IsInRelationshipsMode() const;

    /// Return true if this collection is *expression-mode*.  That is, if it
    /// uses the `membershipExpression` attribute to determine membership and
    /// not the `includes` and `excludes` relationships.  This is the case when
    /// the `mode` attribute is set to `expression`, or when the mode attribute
    /// is set to `automatic` and none of the relationship-mode related
    /// properties are authored.  Equivalent to `!IsInRelationshipsMode()`.
    bool IsInExpressionMode() const {
        return !IsInRelationshipsMode();
    }

    /// Returns all the usd objects that satisfy the predicate, \p pred in the
    /// collection represented by the UsdCollectionMembershipQuery object, \p
    /// query.
    /// 
    /// The results depends on the load state of the UsdStage, \p stage.
    USD_API
    static std::set<UsdObject> ComputeIncludedObjects(
        const UsdCollectionMembershipQuery &query,
        const UsdStageWeakPtr &stage,
        const Usd_PrimFlagsPredicate &pred=UsdPrimDefaultPredicate);

    /// Returns all the paths that satisfy the predicate, \p pred in the
    /// collection represented by the UsdCollectionMembershipQuery object, \p
    /// query.
    /// 
    /// The result depends on the load state of the UsdStage, \p stage.
    USD_API
    static SdfPathSet ComputeIncludedPaths(
        const UsdCollectionMembershipQuery &query,
        const UsdStageWeakPtr &stage,
        const Usd_PrimFlagsPredicate &pred=UsdPrimDefaultPredicate);

    /// \anchor UsdCollectionAPI_AuthoringAPI
    /// \name Collection Authoring API
    /// 
    /// Convenience API for adding or removing prims and properties to (or 
    /// from) a collection..
    /// 
    /// @{

    /// Includes or adds the given path, \p pathToInclude in the collection. 
    /// 
    /// This does nothing if the path is already included in the collection. 
    /// 
    /// This does not modify the expansion-rule of the collection. Hence, if the 
    /// expansionRule is <i>expandPrims</i> or <i>expandPrimsAndProperties</i>, 
    /// then the descendants of \p pathToInclude will be also included in the 
    /// collection unless explicitly excluded.
    /// 
    /// \sa UsdCollectionAPI::ExcludePath()
    USD_API 
    bool IncludePath(const SdfPath &pathToInclude) const;

    /// Excludes or removes the given path, \p pathToExclude from the collection.
    /// 
    /// If the collection is empty, the collection becomes one that
    /// includes all paths except the givne path.  Otherwise, this does
    /// nothing if the path is not included in the collection. 
    ///
    /// This does not modify the expansion-rule of the collection. Hence, if the 
    /// expansionRule is <i>expandPrims</i> or <i>expandPrimsAndProperties</i>, 
    /// then the descendants of \p pathToExclude will also be excluded from the 
    /// collection, unless explicitly included.
    ///
    /// \sa UsdCollectionAPI::IncludePath()
    USD_API
    bool ExcludePath(const SdfPath &pathToExclude) const; 

    /// @}
    
    /// Validates the collection by checking the following rules:
    /// * a collection's expansionRule should be one of "explicitOnly", 
    ///   "expandPrims" or "expandPrimsAndProperties".
    /// * a collection should not have have a circular dependency on 
    ///   another collection.
    /// * a collection should not have both includes and excludes
    ///   among its top-level rules
    USD_API 
    bool Validate(std::string *reason) const; 

    /// Resets the collection by clearing both the includes and excludes 
    /// targets of the collection in the current UsdEditTarget.
    /// 
    /// \note This does not modify the "includeRoot" attribute which is used 
    /// to include or exclude everything (i.e. the pseudoRoot) in the USD stage.
    USD_API
    bool ResetCollection() const; 

    /// Blocks the targets of the includes and excludes relationships of the 
    /// collection, making it 
    /// <* <i>empty</i> if "includeRoot" is false (or unset) or
    /// * <i>include everything</i> if "includeRoot" is true.
    /// (assuming there are no opinions in stronger edit targets).
    USD_API
    bool BlockCollection() const;

    /// Test whether a given \p name contains the "collection:" prefix
    ///
    USD_API
    static bool CanContainPropertyName(const TfToken &name);

private:

    // Helper method for computing the UsdCollectionMembershipQuery object for
    // a collection.
    // This makes recursive calls if the collection includes other collections.
    // \p chainedCollectionPaths is used to pass in the set of all seen and
    // included collections in the dependency chain and is used to detect
    // circular dependencies.
    // If \p foundCircularDependency is not nullptr, it is set to true if a
    // circular dependency is detected amongst the included collections.
    // If it is nullptr, a warning is issued when a circular dependency is
    // detected.
    void _ComputeMembershipQueryImpl(
        UsdCollectionMembershipQuery *query,
        const SdfPathSet &chainedCollectionPaths,
        bool *foundCircularDependency=nullptr) const;

    // The same as ResolveCompleteMembershipExpression(), but set
    // `foundCircularDependency` to true if a circular dependency is encountered
    // during resolution.
    SdfPathExpression
    _ResolveCompleteMembershipExpression(bool *foundCircularDependency) const;
};

PXR_NAMESPACE_CLOSE_SCOPE

#endif