Authority control method and device for micro-front-end architecture, equipment, medium and product

Abstract

The invention provides an authority control method, device, equipment, medium and product for a micro-front-end architecture, and the method comprises the steps: distributing a unique service code for each sub-application of the micro-front-end architecture, and enabling a sub-route of the sub-application to comprise the unique service code and a sub-path; defining different user roles, and allocating user permissions to the user roles; based on the unique service code and a preset permission rule, configuring a routing permission for the sub-application through a content delivery network (CDN); generating a dynamic routing table through a recursive algorithm based on the user permission and the routing permission; and receiving an access request from a user, and determining whether the user has permission to access the sub-application based on the dynamic routing table and the user role.

Description

Technical Field

[0001] The present application relates to the field of computers, and in particular to a permission control method, apparatus, device, medium, and product for a micro-front-end architecture. Background Art

[0002] In complex business scenarios and with numerous permission categories, front-end projects based on a micro-frontend architecture face numerous challenges in controlling permissions for individual routes across multiple independently deployed business sub-applications. Existing technologies require each sub-application's corresponding business entity to process permission status determined on the backend, then determine the displayed page or issue a permission blocking prompt based on the permission error code. This increases development costs and creates a lot of duplication within the system. Summary of the Invention

[0003] This application proposes a permission control method for a micro-frontend architecture to improve the permission judgment of the existing micro-frontend architecture.

[0004] The method includes: assigning a unique service code to each sub-application of the micro-frontend architecture, wherein the sub-route of the sub-application includes the unique service code and a sub-path; defining different user roles and assigning user permissions to the user roles; configuring routing permissions for the sub-application through a content delivery network (CDN) based on the unique service code and preset permission rules; generating a dynamic routing table through a recursive algorithm based on the user permissions and the routing permissions; receiving an access request from a user, and determining whether the user has permission to access the sub-application based on the dynamic routing table and the user role.

[0005] Optionally, generating a dynamic routing table by a recursive algorithm based on the user authority and the routing authority includes:

[0006] Filter the sub-routes corresponding to the sub-applications that are inaccessible to the user;

[0007] Incorporating the routing authority into the routing structure of the sub-router;

[0008] The dynamic routing table is generated by the recursive algorithm.

[0009] Optionally, receiving an access request from a user and determining, based on the dynamic routing table and the user role of the user, whether the user has permission to access the sub-application includes:

[0010] Setting a routing guard middleware, which determines whether to respond to the user's request through a hook function according to the dynamic routing table;

[0011] Encapsulate a high-order component, the high-order component receives the sub-path, and before rendering the page of the sub-application corresponding to the sub-path, determines whether to render the page of the sub-application requested to be accessed according to the dynamic routing table.

[0012] Optionally, the routing authority includes service error routing and routing whitelist.

[0013] Optionally, the business error routing includes an error code mapping table, the error code mapping table includes a first error code, a second error code and a third error code, the first error code indicates that the login is not completed or the session has expired, the second error code indicates that the resource does not exist, and the third error code is a custom error code.

[0014] Optionally, when it is determined that the page of the sub-application is not to be rendered, a corresponding error routing page is generated based on the error code mapping table, and the page accessed by the user is directed to the error routing page.

[0015] Optionally, after the permission rule is updated, the CDN automatically updates the configured routing permission based on a preset cache time.

[0016] Optionally, the updated routing authority configured by the CDN is received, and the dynamic routing table is updated.

[0017] Optionally, the permission rule includes the user role required to perform a specified operation on the sub-application.

[0018] This application also proposes a permission control device for a micro-frontend architecture, wherein the micro-frontend architecture includes a base and a sub-application, and further includes:

[0019] a routing identification unit configured to assign a unique service code to each sub-application of the micro-frontend architecture, wherein the sub-route of the sub-application includes the unique service code and a sub-path;

[0020] a user rights unit configured to define different user roles and assign user rights to the user roles;

[0021] a routing permission unit configured to configure routing permissions for the sub-application via a content delivery network (CDN) based on the unique service code;

[0022] A dynamic routing unit configured to generate a dynamic routing table through a recursive algorithm based on the user authority and the routing authority;

[0023] The permission determination unit is configured to receive an access request from a user and determine whether the user has permission to access the sub-application based on the dynamic routing table and the user role.

[0024] The present application also proposes an electronic device, which includes a memory storing computer-executable instructions and a processor; when the instructions are executed by the processor, the device implements any of the methods described above.

[0025] The present application also proposes a computer-readable medium, which stores one or more programs. The one or more programs can be executed by one or more processors to implement any of the methods described above.

[0026] The present application also proposes a computer program product, comprising a computer program, which implements any of the aforementioned methods when executed by a processor.

[0027] Based on the aforementioned permission control method for a micro-frontend architecture and the corresponding apparatus, electronic device, computer-readable medium, and computer program product, this application can dynamically control page access to different sub-applications based on the corresponding permissions of different users, and ensure access security through multiple permission verifications. Furthermore, by assigning user roles and unique service codes and utilizing a CDN for dynamic routing, the speed of permission configuration updates is greatly improved, the rendering time of error pages is shortened, and the performance and usability of web applications are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flowchart of the permission control method according to the implementation method of this application.

[0029] Figure 2 Schematic diagram of a permission control device according to an embodiment of the present application.

[0030] Figure 3 is a schematic diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] Next, the technical solution of this application will be described in detail with reference to the accompanying drawings.

[0032] First, the technical terms involved in this application are explained.

[0033] Micro-frontend architecture: Divide a large front-end application into multiple independent and flexible sub-applications. Each sub-application can be developed, run, and deployed independently, and then combine multiple sub-applications into a single user-oriented application.

[0034] Micro front-end base: The micro front-end base is the core hub of the micro front-end architecture, responsible for unified application scheduling, resource management, and life cycle control of sub-applications. It is referred to as the base.

[0035] Figure 1It is a flowchart of the permission control method for micro front-end architecture.

[0036] In step 101, a unique service code is assigned to each sub-application in the micro-frontend architecture. A sub-route for a sub-application consists of a unique service code and a sub-path. Each sub-application corresponds to a different service in the business domain, such as a restaurant management service, an office management system service, a financial system service, and a human resources system service. Each sub-application includes multiple resources, each with its own functionality and access sub-paths and sub-routes. When registering a sub-application, the base assigns a unique name to the sub-application based on the service code of the sub-application's corresponding service. Based on this name, a unique service code is generated for each resource in the sub-application. For example, the unique service codes corresponding to different resources in the restaurant management service sub-application may include code1, code2, and code3. The unique service code is then combined with the sub-path corresponding to the resource to form a sub-route. For example, the routing address of one resource in the restaurant management service sub-application is code1 / a / b, the routing address of another resource is code2 / a / b, and the routing address of another resource is code3 / a / c. As can be seen, when different resources have the same sub-path, for example, all sub-paths are / a / b, sub-route conflicts can be avoided by setting the unique service code in the sub-route. At the same time, during the subsequent permission verification process, the base needs to parse the full path before it can quickly locate the target sub-application and the sub-application's related permissions through the unique service code.

[0037] In step 102, different user roles are defined, and user permissions are assigned to the user roles. This step is performed in the back-end system. User permissions are used to determine whether users with corresponding user roles have the permission to access the corresponding sub-application page. For each sub-route of each sub-application, a corresponding resource permission code will be configured for each element on its corresponding routing address page, that is, to determine whether the user can access the resource content corresponding to the element, and then the resource permission code will be combined with the user role to generate the user permission. For example, {"role":"admin","accessibleApps":["code1"]} means that the sub-application accessibleApps accessible to users with the user role of administrator is the restaurant management service sub-application code1.

[0038] In step 103, based on the unique service code and the preset permission rules, routing permissions are configured for the sub-application through the content delivery network (CDN). Configuring routing permissions for a sub-application means configuring corresponding routing permissions for each resource in the sub-application. The preset permission rules are set by the micro-frontend administrator, and the permission rules are used to set the user roles required for performing certain operations on a sub-application, or the user roles that have the permission to perform the operations. For example, when performing a setting operation on a resource of the restaurant management service sub-application (for example, through the instruction / setting), it is set that the user must have the user role of an administrator (for example, "admin" identity) to perform the operation.

[0039] Based on the existing permission rules, the permission rules will first be stored according to the unique service code. For example, the whitelist of routing permissions is stored in the following format:

[0040]

[0041]

[0042] The above whitelist indicates that for resource code1 in the restaurant management service sub-application, calling the function route associated with the dashboard requires administrator permissions; calling the function route associated with setting requires manager permissions; and for resource code2 in the restaurant management service sub-application, calling the function route associated with report requires auditor permissions.

[0043] In addition to the whitelist, routing permissions also include business error routing, which is used to import the corresponding error page when there is no permission or an error occurs. The business error routing can include an error code mapping table, which includes the first error code 401 indicating login failure or session expiration, the second error code 404 indicating resource non-existence, and the third error code 403, which can be customized, for example, to indicate no permission to access.

[0044] In step 104, a dynamic routing table is generated by a recursive algorithm based on the user authority and the routing authority.

[0045] Specifically, first, the sub-routes corresponding to the sub-applications that the user rights of the corresponding user role cannot access are filtered. For example, if a user role cannot access the financial system sub-application, the financial system sub-application and its sub-routes are filtered out for this user role.

[0046] Then, the routing permissions are incorporated into the routing structure of the sub-routes. The routing structure is the standardized routing configuration of a sub-application. It describes each route within the sub-application and provides a mapping between routing components. For example, `[{path:"dashboard",component:Dashboard}]` represents the mapping between the path of the dashboard within a sub-application and the routing component Dashboard. For all sub-applications and their corresponding sub-routes, the routing permissions dynamically configured by the CDN are recursively incorporated into the routing structure, thus achieving a combination of routing permissions and routing structure. This allows the dynamic routing table to dynamically adjust the access permissions and corresponding routes between user roles and sub-applications.

[0047] Furthermore, when the micro-frontend administrator modifies permission rules—for example, changing the permissions for the setting operation for resource code1 in the restaurant management service sub-application from admin to super-admin—the change is submitted to the CDN to reconfigure routing permissions. The CDN automatically updates the configured routing permissions after a preset cache time, such as automatically refreshing the new routing permission whitelist after 30 seconds of caching. The base then re-pulls the new routing permission whitelist and dynamically updates the dynamic routing table. When the user navigates to the routing page, dynamic routing takes effect immediately based on the new dynamic routing table without refreshing the page.

[0048] In step 105 , an access request from a user is received, and based on the dynamic routing table and the user role, it is determined whether the user has the authority to access the sub-application.

[0049] In one embodiment, permission determination can be performed using a dual interception approach. First, a routing guard middleware can be set as the first level of interception. For example, when using the React Router routing library, based on the current content of the dynamic routing table, the hook function onRouteChangeBefore can be used to perform permission verification before jumping to the route, thereby determining whether to respond to the user's access request.

[0050] At the same time, a high-order component can also be encapsulated as a second level of interception. The high-order component can receive the sub-path of the sub-application that the user requests to access. Before rendering the page of the sub-application corresponding to the sub-path, it is determined based on the dynamic routing table whether to render the page of the sub-application requested to access. The page of the sub-application will be rendered only when it is determined that the user has the right to access it. Otherwise, the corresponding error routing page will be generated based on the aforementioned error code mapping table, and the page accessed by the user will be redirected to the error routing page. The error routing page can automatically generate situational prompt text based on user roles, user permissions, permission rules, the path requested to access, etc.

[0051] Therefore, through the double interception method, the accuracy of permission judgment and interception is improved to ensure the data security of the micro front-end.

[0052] It is understood that the above steps do not necessarily have to be performed in the order of steps 101 to 105. Instead, they are merely used to describe the control logic of the permission control method and can be performed in any order or simultaneously without affecting the overall process. For example, step 102 can be performed first, followed by step 101.

[0053] Next, using the React platform as an example, we will explain the operational process of the micro-frontend performing permission control on a user's access request to a sub-application in the micro-frontend.

[0054] First, a user authentication service can be set up to obtain user-related information (such as user role information) when the user logs in, and store the information in the global state management library to facilitate access to the information in various processes of permission control.

[0055] Once a user logs in, all page routing resources for the sub-application the user requested are available, including the sub-application's routing configuration, corresponding page components, navigation components, etc. At the same time, the CDN's configured routing permission whitelist and business error routing are retrieved to match the user permissions corresponding to the user's role, and the corresponding page access permissions are assigned.

[0056] The micro-frontend architecture system then dynamically registers or updates the React Router dynamic routing table based on routing permissions and the permission rules set by the micro-frontend administrator. Due to user requests, the access route will change to the requested sub-route page. At this point, a double interception process will be used to determine whether to redirect and render the requested page, preventing unauthorized users from viewing the static resources of that page. If the user is determined to have access to the corresponding page, the route is redirected to that page and rendered. If the user is determined to have no access permissions or an error occurs during the access, the route is redirected to an error page, which is rendered according to the error code mapping table. For example, in the aforementioned example, if the permissions for the settings operation in the restaurant management service sub-application code1 are changed from admin to super-admin, a user with standard admin permissions accessing the corresponding route code1 / settings will trigger a third error code 403, which is customized to indicate no access permissions. The route will be redirected to the error page, and the error message "super=admin role required" will be rendered on the error page.

[0057] Another aspect of the present application provides a permission control device 200 for a micro front-end architecture, wherein the micro front-end architecture includes a base and a sub-application. Figure 2 As shown, the authority control device 200 includes:

[0058] The route identification unit 201 is configured to assign a unique service code to each sub-application of the micro-frontend architecture, wherein the sub-route of the sub-application includes a unique service code and a sub-path.

[0059] The user rights unit 202 is configured to define different user roles and assign user rights to the user roles.

[0060] The routing permission unit 203 is configured to configure routing permissions for the sub-application through a content delivery network (CDN) based on the unique service code.

[0061] The dynamic routing unit 204 is configured to generate a dynamic routing table through a recursive algorithm based on user permissions and routing permissions.

[0062] The permission determination unit 205 is configured to receive an access request from a user and determine whether the user has permission to access the sub-application based on the dynamic routing table and the user role.

[0063] It is understandable that the permission control device 200 can run on various computers and servers, and can use the aforementioned permission control method to perform dynamic permission control management in the micro-front-end architecture.

[0064] Now refer to Figure 3 , which is a block diagram of an electronic device 300 according to one embodiment of the present application. The electronic device 300 may include one or more processors 302, a system control logic 308 connected to at least one of the processors 302, a system memory 304 connected to the system control logic 308, a non-volatile memory (NVM) 306 connected to the system control logic 308, and a network interface 310 connected to the system control logic 308.

[0065] The processor 302 may include one or more single-core or multi-core processors. The processor 302 may include any combination of general-purpose processors and special-purpose processors (e.g., graphics processors, application processors, baseband processors, etc.). In the embodiments of this document, the processor 302 may be configured to execute one or more embodiments of the permission control method proposed in this application.

[0066] In some embodiments, system control logic 308 may include any suitable interface controller to provide any suitable interface to at least one of processors 302 and / or any suitable device or component in communication with system control logic 308 .

[0067] In some embodiments, the system control logic 308 may include one or more memory controllers to provide an interface to the system memory 304. The system memory 304 may be used to load and store data and / or instructions. In some embodiments, the system memory 304 of the electronic device 300 may include any suitable volatile memory, such as a suitable dynamic random access memory (DRAM).

[0068] The non-volatile memory 306 may include one or more tangible, non-transitory computer-readable media for storing data and / or instructions. In some embodiments, the non-volatile memory 306 may include any suitable non-volatile memory such as flash memory and / or any suitable non-volatile storage device, such as at least one of an HDD (Hard Disk Drive), a CD (Compact Disc) drive, and a DVD (Digital Versatile Disc) drive.

[0069] The non-volatile memory 306 may include a portion of storage resources installed on the device of the electronic device 300, or it may be accessible to the device but not necessarily a part of the device. For example, the non-volatile memory 306 may be accessed over a network via the network interface 310.

[0070] In particular, system memory 304 and non-volatile memory 306 may each include a temporary copy and a permanent copy of instructions 320. Instructions 320 may include instructions that, when executed by at least one of processors 302, cause electronic device 300 to implement the methods provided herein. In some embodiments, instructions 320, hardware, firmware, and / or software components thereof may additionally or alternatively be located in system control logic 308, network interface 310, and / or processor 302.

[0071] In some embodiments, the network interface 310 may be integrated with other components of the electronic device 300. For example, the network interface 310 may be integrated with at least one of the processor 302, the system memory 304, the non-volatile memory 306, and a firmware device (not shown) having instructions. When at least one of the processors 302 executes the instructions, the electronic device 300 implements one or more embodiments of the permission control method described herein. The network interface 310 may further include any suitable hardware and / or firmware to provide a multiple-input multiple-output radio interface.

[0072] In one embodiment, at least one of the processors 302 may be packaged together with logic for one or more controllers of the system control logic 308 to form a system-in-package (SiP). In one embodiment, at least one of the processors 302 may be integrated on the same die with logic for one or more controllers of the system control logic 308 to form a system-on-chip (SoC).

[0073] The electronic device 300 may further include an input / output (I / O) device 312. The input / output (I / O) device 312 may include a user interface to enable a user to interact with the electronic device 300; and a peripheral component interface may be designed to enable peripheral components to interact with the electronic device 300.

[0074] In some embodiments, the user interface may include, but is not limited to, a display (e.g., an LCD display, a touch screen display, etc.), a speaker, a microphone, one or more cameras (e.g., a still image camera and / or a video camera), a flashlight (e.g., an LED flash), and a keyboard.

[0075] In some embodiments, the peripheral component interface may include, but is not limited to, a non-volatile memory port, an audio jack, and a power interface.

[0076] It should be understood that the structure illustrated in the embodiment of the present invention does not constitute a specific limitation on the electronic device 300. In other embodiments of the present application, the electronic device 300 may include more or fewer components than shown, or may combine or separate certain components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0077] Program code can be applied to input instructions to perform the functions described herein and generate output information. The output information can be applied to one or more output devices in a known manner. For the purposes of this application, a processing system includes any system having a processor such as, for example, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), or a microprocessor.

[0078] Program code can be implemented with a high-level programming language or an object-oriented programming language to communicate with the processing system. Where necessary, program code can also be implemented with assembly language or machine language. In fact, the mechanism described herein is not limited to the scope of any particular programming language. In either case, the language can be a compiled language or an interpreted language.

[0079] One or more aspects of at least one embodiment may be implemented as representative instructions stored on a computer-readable storage medium, which represent various logic within a processor and, when read by a machine, causes the machine to fabricate logic for performing the techniques described herein. These representations, known as "IP cores," may be stored on a tangible, computer-readable storage medium and supplied to various customers or manufacturing facilities to load into fabrication machines that actually manufacture the logic or processor.

[0080] An embodiment of the present application discloses a computer-readable medium storing one or more programs executable by one or more processors to implement the permission control method of the present application.

[0081] An embodiment of the present application discloses a computer program product, including a computer program, which implements the permission control method of the present application when executed by a processor.

[0082] The above is an explanation of the embodiments of the present application by specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Although the description of the present application will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this embodiment. In addition, in order to avoid confusion or blurring the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other unless there is a conflict.

[0083] Furthermore, various operations will be described as multiple discrete operations in a manner that is most helpful in understanding the illustrative embodiments; however, the order of description should not be construed as implying that these operations are necessarily order dependent. In particular, these operations do not need to be performed in the order presented.

[0084] Unless the context dictates otherwise, the terms "comprising," "having," and "including" are synonymous. The phrase "A / B" means "A or B." The phrase "A and / or B" means "(A and B) or (A or B)."

[0085] As used herein, the term "module" or "unit" may refer to, be or include: an application specific integrated circuit (ASIC), an electronic circuit, a (shared, dedicated or group) processor and / or memory that executes one or more software or firmware programs, a combinational logic circuit and / or other suitable components that provide the described functionality.

[0086] In the accompanying drawings, some structural or method features are shown in a specific arrangement and / or order. However, it should be understood that such specific arrangement and / or order may not be required. In some embodiments, these features may be arranged in a manner and / or order different from that shown in the illustrative drawings. In addition, the inclusion of structural or method features in a particular figure does not imply that such features are required in all embodiments, and in some embodiments, these features may not be included or may be combined with other features.

[0087] It should be understood that although the terms "first," "second," and the like may be used herein to describe various elements or data, these elements or data should not be limited by these terms. These terms are used only to distinguish one feature from another. For example, a first feature may be referred to as a second feature, and similarly, a second feature may be referred to as a first feature without departing from the scope of the exemplary embodiments.

[0088] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0089] While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

1. A permission control method for a micro-frontend architecture, characterized in that: include: Assigning a unique service code to each sub-application of the micro-frontend architecture, wherein a sub-route of the sub-application includes the unique service code and a sub-path; Define different user roles and assign user permissions to said user roles; Based on the unique service code and preset permission rules, configuring routing permissions for the sub-application through a content delivery network (CDN); Based on the user authority and the routing authority, a dynamic routing table is generated by a recursive algorithm; An access request from a user is received, and based on the dynamic routing table and the user role, it is determined whether the user has permission to access the sub-application.

2. The method according to claim 1, characterized in that Generating a dynamic routing table based on the user authority and the routing authority by a recursive algorithm includes: Filter the sub-routes corresponding to the sub-applications that are inaccessible to the user; Incorporating the routing authority into the routing structure of the sub-router; The dynamic routing table is generated by the recursive algorithm.

3. The method according to claim 1, characterized in that Receiving an access request from a user and determining, based on the dynamic routing table and the user role of the user, whether the user has permission to access the sub-application includes: Setting a routing guard middleware, which determines whether to respond to the user's request through a hook function according to the dynamic routing table; Encapsulate a high-order component, the high-order component receives the sub-path, and before rendering the page of the sub-application corresponding to the sub-path, determines whether to render the page of the sub-application requested to be accessed according to the dynamic routing table.

4. The method according to claim 3, characterized in that The routing permissions include service error routing and routing whitelist.

5. The method according to claim 4, characterized in that The business error routing includes an error code mapping table, which includes a first error code, a second error code, and a third error code. The first error code indicates that the login is not complete or the session has expired, the second error code indicates that the resource does not exist, and the third error code is a custom error code.

6. The method according to claim 5, characterized in that When it is determined that the page of the sub-application is not to be rendered, a corresponding error routing page is generated based on the error code mapping table, and the page accessed by the user is directed to the error routing page.

7. The method according to claim 1, characterized in that After the permission rules are updated, the CDN automatically updates the configured routing permissions based on a preset cache time.

8. The method according to claim 7, characterized in that Receive the updated routing authority configured by the CDN, and update the dynamic routing table.

9. The method according to claim 8, characterized in that The permission rule includes the user role required to perform a specified operation on the sub-application.

10. A permission control device for a micro-frontend architecture, wherein the micro-frontend architecture includes a base and a sub-application, characterized in that: include: a routing identification unit configured to assign a unique service code to each sub-application of the micro-frontend architecture, wherein the sub-route of the sub-application includes the unique service code and a sub-path; a user rights unit configured to define different user roles and assign user rights to the user roles; a routing permission unit configured to configure routing permissions for the sub-application via a content delivery network (CDN) based on the unique service code; A dynamic routing unit configured to generate a dynamic routing table through a recursive algorithm based on the user authority and the routing authority; The permission determination unit is configured to receive an access request from a user and determine whether the user has permission to access the sub-application based on the dynamic routing table and the user role.

11. An electronic device, characterized in that: The device comprises a memory storing computer-executable instructions and a processor; when the instructions are executed by the processor, the device implements the method according to any one of claims 1 to 9.

12. A computer-readable medium, characterized in that The computer-readable medium stores one or more programs, and the one or more programs can be executed by one or more processors to implement the method according to any one of claims 1 to 9.

13. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 9 is implemented.

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