The content of the invention
To achieve these goals, according to an aspect of the invention, there is provided a kind of cloud atomic unit is delivered and deploymentMethod.
The cloud atomic unit be one can independent operating minimum cloud service cell cube, comprising service entities (GIS takeBusiness) and operation service environment.Cloud atomic unit provides service ability description, service status information by service interface, passes throughResource interface provides virtual resources demand and status information, and by data access interface the number in unified storage system is accessedAccording to.
Cloud atomic unit is by cloud atomic unit VM template generations.The cloud atomic unit VM templates encapsulate cloud atomic unitWhole environment composition required for operation, its inside is soft mainly to include VME operating system, middleware container, GIS serverSystem and related system configuration, adjoint service system and cloud service operational system.Wherein, GIS server system mainly provides groundFigure service and geoanalysis service.Map Services mainly provide the acquisition of map datum, the main net for including meeting international standardNetwork Map Services (WMS), network map tile service (WMTS) and web feature service (WFS) etc..Geoanalysis service masterGeodata analytic function is provided, for the computing of complicated map datum, analysis etc., including network processes service (WPS),Reason network analysis service, space three-dimensional Analysis Service etc..
The present invention is using the service system framework based on cloud atomic unit.It is main including cloud service fortune in described frameworkMaintain system and cloud Resource directory center.
Cloud service operational system mainly has cloud resource subscription module, user management module, Service Management and proxy module, clothesBusiness display module and O＆M supporting module.Cloud resource subscription resume module service publisher ordered with the identity application of cloud tenantThe cloud resource required for issuing service is read, such as storage and computing resource.User management module is responsible for creating all types of user and dimensionShield subscriber data.Service management module mainly includes service registry, service examination ＆ verification, classification of service, Service Statistics, service metadataThe function such as synchronous.The core of proxy module is, using reverse proxy mechanism, third party's service to be polymerized, is managed collectively.ClothesBusiness display module provides service search, service subscription and shows the functions such as the service effectiveness that user obtains.O＆M supporting moduleEach cloud atomic unit, service, the real data of user when mainly being run by gathering system, monitor in real time is whole with analysisSystem running state, including service access monitoring, server state monitoring, User operation log management etc. function.
Cloud Resource directory center relies on bottom cloud computing basic platform to be integrated to various information resource and Unified SetMiddle management.Resource layer, resource management layer and resource access interface layer can be divided into, wherein, resource layer include the cloud platform communication resource,GIS service resource, cloud basic resource and cloud atomic unit resource etc..Resource pool management layer provides the function of management resource, according toAction type is divided into resource registering, planning, delivers and the generic operation of O＆M four.Resource access interface layer provides unified service accessInterface, including resource registering interface, MRP interface, resource delivery interface, resource O＆M interface.
Cloud atomic unit is delivered and includes resource registering the step of deployment, by the metadata information of cloud atomic unit and operationResource information needed for cloud atomic unit is registered to Resource directory center；MRP, by the related resource tool of cloud atomic unitBody, instantiation；Cloud atomic unit is delivered, and cloud atomic unit will become actual available resource after the completion of delivery, and each cloud is formerSpecific GIS service example is run in subelement the inside；Resource O＆M, the operation management operation to each cloud atomic unit willThe operation management operation of the GIS service example being associated with inside it.
Further, cloud atomic unit resource registering operation includes registering the operation of cloud interface and tenant's information, for realityExisting Resource directory center and bottom cloud computing platform interface communication；The operation of registration GIS service disposition data source, for positioningConfiguration database information needed for GIS service, is that the GIS service planning of following cloud atomic unit is prepared；Registration GIS serviceThe operation of data source, the tile or vector database information needed for for positioning GIS service；The behaviour of registration GIS service metamessageMake, for registering the information such as GIS service species, numbering；The operation of registration GIS service VM template, for by different GIS service classesThe corresponding VM templates of type are uploaded in corresponding cloud platform, and by the corresponding information registering of VM templates to Resource directory center；The operation of registration cloud basic resource, for by the cloud basic resource such as the calculating used in different type GIS service, network and storageAllocative decision is registered to Resource directory center.
Further, cloud atomic unit MRP includes that the GIS service of cloud atomic unit is planned, for according to cloud atomGIS service type, service name, GIS service data corresponding to unit is arranged and generates corresponding GIS service configuration information, andThe configuration information is entered into into Resource directory center；The cloud basic resource planning of cloud atomic unit, for according to cloud atomic unitCorresponding GIS service planning, selects corresponding calculating, storage and network foundation resource；The title planning of cloud atomic unit, is used forResource directory center and cloud computing platform carry out network positions using the title of cloud atomic unit to it；The quantity of cloud atomic unitPlanning, for supporting resource polymerization and scheduling, and is extended to GIS service example, reaches and once deliver multiple same typesThe purpose of cloud atomic unit.
Further, when cloud atomic unit resource is delivered, according to the planning information of previous step cloud atomic unit, correspondence is generatedGIS service VM example.
Further, after the completion of the delivery of cloud atomic unit, its internal cloud service operational system can be according to the time cycleOr external condition triggering, actively or passively to Resource directory center report its CPU, internal memory, network bandwidth flowDeng O＆M status information, these O＆M information are notified resource polymerization and scheduler module by Resource directory center, and the latter is according to judgeIndex determines to carry out elastic telescopic process to cloud atomic unit resource.
According to a further aspect in the invention, the application apparatus that a kind of cloud atomic unit is delivered and disposed is additionally provided.
In the device of the delivery of cloud atomic unit and the deployment of the present invention, cloud atomic unit will be counted as calculating containerThe configuration data and GIS data for calculating needs is external.So be conducive to each role of calculating service routine (such as computing, numberAccording to role) separate, with loose framework composition service cluster.The framework of loose coupling can reduce resource on to greatest extent and damageConsumption, meanwhile, each cloud atomic unit can configure cloud platform numerical procedure according to the performance requirement of self-role.
Further, need to set up independent data-storage system during actual deployment, storage content includes cloud atomic unitThe data source configuration and the storage of GIS service data source of service, all of cloud atomic unit and cloud service are shared the data and are depositedStorage system.
Further, cloud atomic unit deliver with deployment when adopt CentOS operating systems, virtual chemical industry VMWare tool,Cloudstack basis cloud platform, MySQL Server data base management systems, GIS service operational system GeoGlobe, systemEnvironment also includes Apache Tomcat Server, Apache Http Server, JDK etc..
Further, cloud atomic unit is delivered has with the work mainly included during deployment：Cloud Resource directory center is set up, is bornDuty is safeguarded all cloud atomic unit masterplate maintenances, the delivery of cloud atomic unit, the establishment of GIS service and is issued and management, GISThe maintenance of service data source；Cloud atomic unit is delivered, by setting up cloud atomic unit system VM masterplate, unified cloud atom is set upCellular system delivers pattern；Deployment cloud service, in cloud atomic unit delivery process, cloud Resource directory center simultaneously takes GISBusiness management module is deployed in cloud atomic unit, and cloud Resource directory center service management module is by calling each cloud atomic unitUnified interface carry out the establishment of cloud service and issue, and for cloud service in uniform data storage system registration service parameter withData source；Instantiation cloud service, cloud service deployment after the completion of, according to the service numerical procedure of user configure cloud service operation withExpansion scheme, arranges spreading parameter, completes the instantiation of cloud service.
Beneficial effect
The present invention integrates GIS service and cloud computing resources using Intel Virtualization Technology, cloud atomic unit is built, by cloud atomDelivery of the unit under privately owned cloud environment and deployment, solve the problems, such as Distributed Services release quickly, renewal, delete and safeguard.
The service arrangement environment set up using cloud atomic unit, can flexibly process service computing request, by serviceAggregation Proxy, request segmentation user's request are submitted to respectively different cloud atomic units and are processed, and can fully be utilizedThe computing resource of cloud platform, substantially increases the processing speed of service.When system is expanded, the addition of new resources also can divideThe computing pressure of load existing resource, and then directly improve the treatment effeciency of whole system.
Specific embodiment
(1) cloud atomic unit structure
Cloud atomic unit be one can independent operating service unit body, comprising service entities (GIS service) and operation clothesThe environment of business, as shown in Figure 1.Cloud atomic unit provides service ability description, service status information by service interface, by moneySource interface provides virtual resources demand and status information, and by data access interface the data in unified storage system are accessed.
Cloud atomic unit has run specific GIS service by cloud atomic unit VM template generations, is an independent serviceNode.Cloud atomic unit VM templates encapsulate the whole environment composition required for the operation of cloud atomic unit, using installing in advance, match somebody with somebodyPut and packed with virtual disk mirror-image format, in cloud environment deployment manual intervention is not needed.It is internal soft main including voidThe configuration of plan machine operating system, middleware container, GIS server system and related system, adjoint service system and O＆M service systemSystem.
(1) GIS server system
GIS server system mainly provides Map Services and geoanalysis service.Map Services mainly provide map datumAcquisition, main Map Service of Network (WMS), network map tile service (WMTS) and the network for including meeting international standardFeature Service (WFS) etc..Geoanalysis service is main to provide geodata analytic function, for the computing of complicated map datum,Analysis etc., including network processes service (WPS), geographical network Analysis Service, space three-dimensional Analysis Service etc..
(2) with service system
It is with the Main Function of service system work：
A) corresponding cloud atomic unit GIS service configuration information is searched according to cloud atomic unit VM examples
B) corresponding configuration information is fetched locally from Resource TOC
C) it is applied to locally configured in service moulding plate bag so as to run into certain certain types of GIS service
(3) O＆M service system
After the completion of cloud atomic unit is delivered, cloud Resource directory center needs the operation shape for grasping cloud atomic unit resource in real timeState.The effect of O＆M service system is exactly actively or passively to give cloud resource by the O＆M status information reporting of cloud atomic unitCatalogue center, and transfer to cloud Resource directory center to be processed accordingly according to feedback result.
(2) the service system framework based on cloud atomic unit
The service system framework based on cloud atomic unit that the present invention is adopted is as shown in Figure 2.It is main in described frameworkIncluding cloud service operational system and cloud Resource directory center, wherein, cloud service operational system is the intermediate axle of user and cloud serviceBeam, on the one hand provides service issue required resource to service publisher, realizes that cloud service is polymerized, and forms unified service emptyIntend address, set up unified service node, and be registered to cloud Resource directory center, there is provided service ability.On the one hand it is responsible for userManagement, is that user gives the authority for accessing cloud service, according to service user's search and the request of subscription service, and to user'sService access request carries out authority identification and accesses the statistics of record, submits request to actual cloud service node.Cloud resourceCatalogue center relies on bottom cloud computing basic platform to be integrated to various information resource and unified centralized management.
(1) cloud service operational system
Cloud service operational system mainly has cloud resource subscription module, user management module, Service Management and proxy module, clothesBusiness display module and O＆M supporting module.
Cloud resource subscription module
Cloud resource subscription resume module services publisher with the cloud required for the identity application subscription issuing service of cloud tenantResource, such as storage and computing resource.During cloud resource bid, cloud tenant needs to submit the data in unified storage system, thenBy cloud resource subscription module, hardware configuration, the quantity of cloud atomic unit, COS, the association required for issuing service is selectedView and service data source, the application after system manager's examination ＆ verification obtains hardware and the system resource that data, services are issued, finallyIssuing service, creates cloud atomic unit.
User management module
User management module is responsible for creating all types of user and safeguards subscriber data, and user perspective is broadly divided into three major types：
System manager
System manager is responsible for the management of whole cloud platform and safeguards.System manager's authority mainly includes private clound resourceCloud atomic unit masterplate is managed and safeguards, examination ＆ verification service is issued, examination ＆ verification service subscription application etc..
Cloud platform tenant (service publisher)
Service publisher is according to actual data processing needs by renting the issue that cloud atomic unit is serviced.Yun PingPlatform tenant authority mainly includes that cloud atomic unit is rented in application, and application is rented by cloud atomic unit in system manager's examination ＆ verificationAfterwards, cloud platform tenant just has the right to use of cloud atomic unit, and clothes are issued in cloud atomic unit using service issuing functionBusiness.Each service can possess multiple expanding nodes in cloud atomic unit, and expanding node is more, and service processing ability is justIt is higher.
Service user
Service user retrieves the service for needing by service search function, carries out service subscription, including subscription serviceUse range, time, figure layer and required resource load ability etc..After authentication, service is used system managerPerson i.e. can be using service.
Service Management and proxy module
Service management module mainly includes：Service registry, service examination ＆ verification, classification of service, Service Statistics, service metadata are sameThe functions such as step.Service registry includes the abilities such as application for registration, editor and the deletion of service metadata, is noted by system manager's examination ＆ verificationVolume, application is nullified, information and service ability of service metadata etc. are verified.Service metadata synchronizing function is mainly usedIn management branch website, including site registration, renewals, delete and query function, and the metadata of website can be carried out manually togetherStep or Timing Synchronization.
The core of proxy module is, using reverse proxy mechanism, third party's service to be polymerized, is managed collectively, and is divided into generationReason Service Management and agency service network sub-module.Agency service manages submodule and obtains service group letter from cloud Resource directory centerBreath, by aggregating algorithm, generates a unique agency service (service aggregating), and address of service is registered to into Service Management mouldBlock, provides the user the final address of service.Agency service network sub-module is used for the address of service of analysis request, is servicedActual address list, and by load balancing agent algorithms, detect the service load situation of each cloud atomic unit, enterThe delivery forwarding of row service, the service request for making user is ultimately routed on the served processing nodes of private clound.
Service display module
Service display module provides service search, service subscription and shows the functions such as the service effectiveness that user obtains.ClothesThe user that make sures obtains the service for needing by service search function, and carries out service subscription.Service search support keyword query,The way of search of the various ways such as space querying, time range inquiry, classification of service inquiry.Service Management is connecing with proxy moduleAfter receiving the service request of service user and subscribing to, to service user the virtual address of agency service is returned.Service is usedAfter person is serviced, the details that can be checked, including service metadata information, service capability information, cartographic information etc..
O＆M supporting module
Each cloud atomic unit, service, the actual number of user when O＆M supporting module is mainly run by gathering systemAccording to, monitor in real time and analysis whole system running status, including service access monitoring, server state monitoring, user operation dayThe functions such as will management.
(2) cloud Resource directory center
Cloud Resource directory center relies on bottom cloud computing basic platform to be integrated to various information resource and Unified SetMiddle management.Resource layer, resource pool management layer and resource access interface layer can be divided into, wherein, resource layer includes cloud platform communication moneySource, GIS service resource, cloud basic resource and cloud atomic unit resource etc..
The cloud platform communication resource
Cloud Resource directory center does not rely on specific cloud computing platform, and it is provided to various using the cloud platform communication resourceThe support of cloud computing platform (such as VMWare VCloud, Apache CloudStack).Cloud platform communication resource management layer isOne level of abstraction, compatible various IaaS cloud platform interfaces, in data bottom the flexibility of service and cross-platform characteristic are increased.CloudPlatform communication resource mainly includes following information：
● cloud platform interface message
Concrete network communication address, port and protocol of the cloud platform interface message comprising cloud platform.Cloud platform is for differenceUser different access interfaces are provided.
For cloud tenant, cloud platform provides cloud atomic unit and rents interface and service issuing interface for it, and cloud is rentedFamily submits the lease request of cloud atomic unit to by renting application to system, after obtaining the access right of cloud atomic unit, passes throughThe issue that service issuing interface is serviced.
For service user, cloud platform provides the service request handling interface of cloud atomic unit for it, and service makesUser submits Service Source request for utilization to by service subscription function, after obtaining the access right for servicing, by aggregated service generationReason forwarding, using the service of cloud atomic unit.
● cloud tenant's information management
Cloud Resource directory center is set firstly the need of tenant's information is registered by tenant's information acquisition cloud basisApply resource allocation and access right.System manager distributes cloud atomic unit according to request for tenant.Cloud platform tenant utilizes cloudAtomic unit rents interface and obtains rental cloud atomic unit, and using service issuing interface its service is issued.
GIS service resource
GIS service resource includes all data, services configuration informations related to GIS service, including GIS service configuration numberAccording to source, GIS data source, GIS service metamessage, GIS service VM Template Information etc..
Cloud basic resource
Cloud basic resource refers to cloud computing virtualization basic resource and its allocation strategy needed for the operation of GIS service VM, such asVirtual cpu, internal memory, disk and the network information, mainly including computing resource, storage resource and Internet resources etc..
Cloud atomic unit resource
Cloud atomic unit is to carry concrete GIS service resource information and cloud basic resource information, and logical using cloud platformThe VM instance objects that letter resource is generated.Cloud atomic unit corresponds to specific GIS service VM example, and its Resource Properties is mainly includedThe information of two aspects：
● the base attribute information of cloud atomic unit
Title comprising VM, ID numberings, description information and GIS service resource information associated with it and cloud basis moneySource information.
● the O＆M information of cloud atomic unit
The O＆M packet of cloud atomic unit contains real-time service operation state, CPU, internal memory and network consumption information.The O＆M information of cloud atomic unit is polymerized for cloud and provide GIS service real time information with scheduling, is cloud atomic unit elastic telescopicMain Basiss.
Resource pool management layer provides the function of management resource, is divided into resource registering, planning according to action type, delivers and transportTie up four generic operations.Wherein, first three generic operation completes speed delivery of the resource in cloud and deployment jointly, and resource O＆M is used to serviceLookup, status monitoring and error tracking and amendment etc..
Resource access interface layer provides unified service access interface, including resource registering interface, MRP interface, moneyDeliver interface, resource O＆M interface in source.
The Core Feature of cloud Resource directory center is exactly delivery, the deployment of service and the cloud atomic unit of cloud atomic unitState control, mainly include that the management of cloud atomic unit, cloud atomic unit are delivered and order management etc..Wherein, cloud atomic unitThe quantity of cloud atomic unit, service name and COS etc. under managing for inquiring about each service group, check each clothesThe details of all cloud atomic units under business group, including the configuration of cloud atomic unit, address of service and system mode etc..It is rightIn each cloud atomic unit, there is provided the operation such as startup, stopping, destruction, and send a message in cloud service operational system.
(3) cloud atomic unit delivers the flow process with deployment
Cloud atomic unit is delivered as shown in Figure 3 with the step of deployment.
Cloud atomic unit is stored in Resource directory center in the form of resource.According to resource process from scratch, Yun YuanSubelement is delivered and includes resource registering the step of deployment, by the metadata information of cloud atomic unit and operation cloud atomic unit instituteThe resource information for needing is registered to Resource directory center；MRP, the related resource of cloud atomic unit is embodied, instantiation；Cloud atomic unit is delivered, and cloud atomic unit will become actual available resource after the completion of delivery, each cloud atomic unit the inside fortuneSpecific GIS service example is gone；Resource O＆M, the operation management operation to each cloud atomic unit will be associated with its insideGIS service example operation management operation.
1. cloud atomic unit resource registering
Cloud atomic unit resource firstly the need of being registered in cloud Resource directory center, deliver and portion by cloud atomic unitThe resource registering operation arrived used in the process of administration is as follows：
(1) cloud interface and tenant's information are registered
Registration cloud interface should be completed with the operation of tenant's information before the operation of all other resource registering, the step operationFor realizing Resource directory center and bottom cloud computing platform interface communication.
(2) GIS service disposition data source is registered
The registration operates the configuration database information needed for for positioning GIS service, is the GIS of following cloud atomic unitService planning is prepared.
(3) GIS service data source is registered
The registration operates the tile or vector database information needed for for positioning GIS service.
(4) GIS service metamessage is registered
The registration is operated for registering the information such as GIS service species, numbering.
(5) GIS service VM template is registered
Corresponding VM templates encapsulation is provided for various GIS service types.By the corresponding VM templates of different GIS service typesIn uploading to corresponding cloud platform, and by the corresponding information registering of VM templates to Resource directory center.
(6) cloud basic resource is registered
The cloud basic resource allocative decision such as the calculating used in different type GIS service, network and storage is registered to into moneySource directory center.
2. cloud atomic unit MRP
(1) the GIS service planning of cloud atomic unit
It is corresponding that GIS service type, service name, GIS service data according to corresponding to cloud atomic unit arranges generationGIS service configuration information, and the configuration information is entered into into Resource directory center, form GIS service planning.
(2) the cloud basic resource planning of cloud atomic unit
According to the corresponding GIS service planning of cloud atomic unit, corresponding calculating, storage and network foundation resource, shape are selectedInto the planning of cloud basic resource.
(3) the title planning of cloud atomic unit
Resource directory center and cloud computing platform carry out network positions using the title of cloud atomic unit to it, it is therefore necessary toEnsure the global name uniqueness of cloud atomic unit.
(4) the quantity planning of cloud atomic unit
For the requirement for supporting resource polymerization to extend to GIS service example with scheduling and other possible operation systems, cloudAtomic unit provides the planning to its quantity, reaches the purpose for once delivering multiple same type cloud atomic units.
3. cloud atomic unit resource is delivered
According to the planning information of previous step cloud atomic unit, corresponding GIS service VM example is generated, delivery process is mainly completeInto following action：
(1) VM examples are generated according to GIS service VM masterplate, completes VM deliveries；
(2) configuration information of GIS service is written in VM examples according to the planning of the GIS service of cloud atomic unit, makes VMGIS service in example can normally start, run, and carry external request, complete the delivery of GIS service；
(3) network positioning information of cloud atomic unit is entered into into Resource directory center, completes the delivery of cloud atomic unit.
4. cloud atomic unit resource O＆M
After the completion of cloud atomic unit is delivered, its internal cloud service operational system can be according to time cycle or outer stripPart is triggered, and actively or passively reports that the O＆M states such as its CPU, internal memory, network bandwidth flow are believed to Resource directory centerThese O＆M information are notified that resource polymerization and scheduler module, the latter are determined to cloud according to judging quota by breath, Resource directory centerAtomic unit resource carries out elastic telescopic process.
(4) cloud atomic unit delivers the application apparatus with deployment
Deliver in the application apparatus with deployment in the cloud atomic unit of the present invention, including cloud atomic unit, cloud service O＆MSystem and cloud Resource directory center.Cloud atomic unit will calculate the configuration data and GIS data for needing as calculating containerIt is external.So be conducive to each role (such as computing, data role) of calculating service routine to separate, constituted with loose frameworkService cluster.Each role can individually become a cloud atomic unit, it is also possible to will be considered as in all same type role setsOne cloud atomic unit.The framework of loose coupling can reduce resource loss on to greatest extent, meanwhile, each cloud atomic unit canCloud platform numerical procedure is configured according to the performance requirement of self-role.
(1) shared data source
GIS data and GIS service configuration data are then external with database form.Using this structure, in deployment cloud atomA database node is at least needed during unit.
Need to set up independent data-storage system during actual deployment, storage content includes the data of cloud atomic unit serviceSource configures and the storage of GIS service data source, and the data-storage system is shared in all of cloud atomic unit and cloud service.
(2) cloud atomic unit delivers the typical environment with deployment
Cloud atomic unit deliver with the operating system, virtualization instrument, basic cloud platform, system environments adopted during deployment,Data base management system, GIS service operational system, as shown in table 1.
The cloud atomic unit of table 1 delivers the typical environment with deployment
(3) the typical integrated scheme of cloud atomic unit
In the typical integrated scheme of cloud atomic unit, mainly including following work：
Set up cloud Resource directory center
Cloud Resource directory center is responsible for safeguarding all cloud atomic unit masterplate maintenances, the delivery of cloud atomic unit, GIS serviceEstablishment with issue and manage, the maintenance of GIS service data source.
Deliver cloud atomic unit
By setting up cloud atomic unit system VM masterplate, wherein comprising CentOS operating systems, JDK, middleware container,GIS service program, adjoint service etc., set up unified cloud atomic unit system and deliver pattern.Cloud Resource directory center reads cloudAtomic unit template establishment cloud atomic unit, disposes operating system in cloud atomic unit, and is needed for cloud service runsSystem environment and system configuration parameter, and corresponding auto-configuration script is write in systems, while determine the position of mount point, andDistribute corresponding Internet resources.
Deployment cloud service
In cloud atomic unit delivery process, it is former that GIS service management module is deployed to cloud by cloud Resource directory center simultaneouslyIn subelement, cloud Resource directory center service management module carries out cloud service by calling the unified interface of each cloud atomic unitEstablishment with issue, and for cloud service in uniform data storage system registration service parameter and data source.
Instantiation cloud service
After the completion of cloud service deployment, cloud service operation and expansion scheme are configured according to the service numerical procedure of user, ifSpreading parameter is put, the instantiation of cloud service is completed.
Finally it should be noted that：Obviously, above-described embodiment is only intended to clearly illustrate the application example, and andThe non-restriction to embodiment.For those of ordinary skill in the field, can also do on the basis of the above descriptionGo out the change or variation of other multi-forms.There is no need to be exhaustive to all of embodiment.And thus drawnAmong protection domain of the obvious change or variation that Shen goes out still in the application type.