A Virtual Enterprise Using Multiagent Systems

Published Date: 02 Nov 2017

Abstract

Information technology and particularly the Internet have changed the way business is done. The Internet offers businesses technical infrastructure that allows an online presence across the globe that can communicate with customers and business partners whenever and wherever they are. The road to global information society, modern company, with the ongoing digitization of information and also develop new techniques of communication, turns into a virtual enterprise or business on the web.

Thus, in this paper we intend to present how to achieve a virtual enterprise by using multi-agent systems. In the first part, we reviewed the concept of virtual enterprise towards the traditional enterprise, highlighting the differences between them, we emphasized the need for and objectives of creating virtual enterprise, the advantages and disadvantages of these types of organizations, after which, we present the design and coordination of the virtual enterprise using multi-agent systems, and we concluded that through these systems can provide effective solutions to very complex problems.

1. Introduction

In the era of globalization, the competition has become fierce in the companies, so enterprises are forced to seek solutions to enter the market with quality products and services at attractive prices, which leads of the permanent decrease of the innovation cycles, permanent changes in market, increasing specialization in individual market segments, increasing cooperation between enterprises.

Due to progress in ICT enterprises have no geographical boundaries and socio-cultural, act on the global market, and dimensioned their resources on the international market. The general trend is to create strategic alliances, in which companies work together to achieve a common goal.

In the context of technological developments, enterprise, main link in the value chain must operate in order to achieve their goals and gain and profit in various ways. However, in the road to modernity, the actual company is the conducting theater of the operations transition towards the future information society global. With the continuous digitization of information, along with the development of new techniques of communication, is increasingly sensed the virtual company or organization web.

2. Virtual enterprise vis-à-vis traditional enterprise

A virtual enterprise can be defined as a temporary alliance of independent companies united by information technology in order to exploit market opportunities. Each partner contributes with their knowledge, understanding and skill in achieving virtual enterprise. When the objective has been achieved or market opportunity disappeared, virtual enterprise is dissolved.

According to Molina and Flores (2000) Virtual enterprise is "a temporary network of independent companies, in connection with each other by means of information technology, by which are divided skills, infrastructure and business processes in order to meet specific market requirements". Virtual enterprise is a subdivision of the network, which it can reconfigure, with own management, productive resources and targets own production.

One can say that a virtual enterprise is a group of companies that decide to form a virtual community, namely platform that allows to sharing information about group members. There are also situations of the enterprise, which address customers via the Internet, which makes from this establishment a virtual enterprise. Typically, such a virtual enterprise is on the value chain: suppliers-producers-customers.

Creating virtual enterprise has appeared as a result of the need to meet the requirements of both the investor who wants to launch into production and consequently on the market a product with short production cycle and cost, as well as organizations with manufacturing activity, which it is, in some participants potential in the virtual enterprise structure to capitalize on maximum production capacity.

To start a traditional business, it takes of the particular physical capital, while for the creating a virtual enterprise starts around a market opportunity, and engages into mesh in generally, more resources than possesses company currently.

Overall, virtual enterprise, from an operational perspective, with the structure and the operational functions and logistics of a traditional enterprise, but appear at the functional level, where it has into account the structure on the "nuclei" of the virtual organization.

In the traditional enterprises all functions necessary to provide products and services developed are integrated into a unified whole, whose major benefit is that all resources and activities are under one the control point (are easily optimized flows of the operations), which allows the integration of the results, monitoring of the activities and making decisions to achieve short and long term objectives.

Disadvantages of the traditional enterprises are determined by the fact that, integration into a single organization of all activities requiring massive capital investment, but also, organizational arrangements for them (vertical - in which each department has its own internal organization, its information system, own management principles), which carries the true internal barriers between departments. The results are reflected in the average satisfaction of the customer, higher costs for serving customers and selling products, which lead to the necessity of implementing a customer relationship management to meet their requirements, both in terms of product and service quality offered and especially of the customer orientation.

To implement a new business idea, is sometimes more profitable to be outsourced or subcontracted the some production processes, than being restructured and re-engineered, which would result in additional costs that the company may not have. In this sense, an option taken into account, is finding partners to conclude an association agreement only to seize appeared market opportunities, or to realize or integrate in a virtual enterprise.

The virtual enterprises does not mean the end of the traditional enterprises, they are business processes, people and technology with varying degrees of connectivity, and the degree of connectivity is higher, with both the enterprise is more virtual, while the border between firms is almost invisible. To be operational and efficient, a virtual enterprise must widely used the Internet, intranet, communication tools (email, teleconferences, etc.), groupware applications, virtual employees with skills in using computers, communication, confidentiality in the activities performed, professionalism and seriousness. In the virtual enterprise, all partners are treated equally, but it can appear the some situations, when the coordinator, which is usually the initiator, has a decisive role in definitive decision, but as a general rule, the decision-making style is open and democratic.

An enterprise with the virtual organizational structure is a form of cooperation between several different enterprises or between their parts. Virtual enterprises can take many forms:

communities which have common interests related through the Internet;

individual businesses grouped by common goals that are located in different geographical areas;

distributed enterprises with independent support systems;

Independent enterprises united to achieve a particular project.

The virtual enterprise depends of the technology infrastructure as much as by the cultural infrastructure - the intellectual capital that facilitates the use of new technologies. For achieving the objective of the virtual enterprise, each component entity, participates with their strong skills (basic) respectively those activities, products, services, technologies, knowledge and skill that are strength and "job heart" of the enterprise.

3. Motivation of achieving virtual enterprises

For setting up a virtual enterprise is important to identify the purpose or motivation of a company to reunite in a network. Motivation can be varied, from expanding company boundaries, to maintain control over vital partners (e.g. for to maintain quality control) or to participate with certain basic skills to divide opportunities by market.

To understand in the real mode, the need to achieve a virtual enterprise, we start from the following situation: we intend to manufacture solid wood furniture of outstanding quality from a relatively cheap raw material. Through the Internet, we find information on places where we can buy raw materials. To transport raw materials, is needed to attract a specialized company, which to transport raw materials to the manufacturer, which will carry furniture for our company.

Our desire is that furniture should be very attractive and useful, to have a nice design, making it necessary, not to employ a team of designers, but to contact an agency of designers who collaborate with us on this project. After finding these partners, remains to be determined where it will loosen market our products. In this regard, to make sure that our products meet customer requirements, we contact a marketing agency to explore the market, it became a strategic partner. To distribute our products, we will not invest money in a retail store, but we will contact the merchants who distribute through their network of shops our products. Following the collaborations made, we can say that we have achieved a virtual enterprise, which is perceived by the population as a very strong company with many employees, expanded manufacturing facilities, wide distribution network etc.

Reasons for the realization of virtual enterprises can be found in various aspects:

 operational flexibility through reaction to changes - the system adapts natural at the changes from the tasks profile, adaptation and learning taking place at the unit level and system level. Flexibility will be guaranteed by changing tasks between units, which provide functional redundancy. Operational independence of the components leads to greater reliability of the whole system. Errors may occur in components, but they will not affect other units, that will function properly;

 high maintainability can be achieved by independent designing for each unit within the virtual company. Where relationship between units, is sufficiently weak, then, their internal design can be effectively encapsulated, leading to the possibility of introducing of changes in the localized mode, where needed, without redesigning the entire system. With a reduction in complexity, by designing smaller units, will increase maintainability and operational independence of components makes possible and facilitates on-line updating of tasks and information.

The initiator of the virtual enterprise, you have to go through the following steps:

• carry out a market study;

• to draw up a business plan, which to base the necessary of the organizational resources for creating virtual enterprise;

•setting parameters that will be met by potential partners;

• Identify potential partners in the market, and making a pre-selection;

• negotiations with selected companies and preparation of data for the second stage of selection;

• data analysis and information on a mathematical model, adapted on the specific product or service in question;

• select organizations that meet the conditions in the required utmost;

• negotiating and concluding contracts for collaboration;

• the team building mixed inter-organizational;

• realization the project (with all steps as are appropriate);

• transfer in production or in manufacturing;

• launching and marketing the product or service;

• dissolution of the virtual enterprise (at the disappearance of market demand, at the decision of the partners, or by transforming a classic supply chain).

In conclusion, to create a virtual enterprise, the investor must take the following steps:

the launch of an application with regard to his desire to produce a product (realize of service), and defining the product / service;

to stating technological specifications and construction of the object;

dialing potential participants, who possess the required technologies in the support list or via a specialized portal, specifying technological requirements imposed;

select the partners between the respondents.

For selecting potential partners, it is important that the initiator to know what, when, who and how to ask:

 what to ask - if co-opting a producer , this must have the operating permits and approvals for raw materials, production lines, storages space, packaging, cargo handling equipment and finished products, possibly auto fleet, marine or railway;

 when ask, initiator (if and coordinates the activities of virtual enterprise) has the obligation to ensure continuous dissemination of accurate and complete information, to all members of the supply chain;

 whose to ask - every member of the virtual enterprise is specialized in something, but also may occur cases when needed experience of a third companies, which have not been taken into account from the beginning (consultation a specialist in commercial law, cooperation with laboratories accredited etc.).

 how to ask - initiator must ask tactfully information, or fulfilling certain tasks, or to act as mediator in case of disagreements between members.

Of the choice of partners in a virtual enterprise is responsible, in the greatest extent, its initiator, in other words the company that has identified a new business opportunity in the market but can not capitalize individual, alone. Virtual enterprise activity will be held in interdisciplinary teams, inter-organizational, which can be geographically distributed. Thus, specialists of the virtual enterprise creates teams, distributed remotely, which using to communicate, virtual environments of the communications.

"Virtual team" designates a group of individuals working together to achieve a common goal, to achieve a innovation or to resolve a problem or a crisis, and which communicate through information and communication technologies, what links some others, beyond the barriers of time, space and cultural differences.

Virtual team must first, to define common goals, establish the agenda, deadlines, responsibility and role of each member individually.

Unlike traditional management teams, the ones virtual may face additional obstacles: cultural differences, communication problems, lack of confidence, insufficient training in communication technologies and so on, for which must consider:

 virtual team leadership, manager acts as a catalyst and coordinator of communication, actively pursuing the emergence of any problems, encouraging the provision of information to all team members. Leaders have an overview of the entire project, and are responsible to inform the team about deadlines, at work status, or any issues arising;

 Creating a climate of trust, there will be an initial workshop which aims to bring all parties together, for to know. Maintaining a climate of trust is the attribute of the team manager, but each member must meet ethical standards of communication undertaken by the group;

 Training of the virtual team members for to collaborate and use of communication information means.

Management activity at the level of virtual enterprises requires a dynamic and flexible allocation of abstract claims by manufacturers and production sites. In this respect, one of the most used methods used in decision-making processes in the virtual enterprises are multiagent methods.

Multiagent systems have their origin in biological and economic systems - like the virtual enterprise - are by their nature distributed (as opposed to hierarchical, feature in the management of the traditional enterprise). Performance is not planned, it stems from interactions between agents. Distributed multiagent systems offer several advantages over traditional systems of the management and control:

 any agent is very close to the real world, being able to track the status their own behavior, no longer needed centralized database, large size;

 agents react only to the local environment, thus, disappearance, adding or the errors to any other agent in the system will not negatively affect the whole system;

 system interacts only with its environment, so the system configuration dependencies are more relaxed than the centralized method;

 the simplicity of the necessary software involves an easier coding.

New information and communication technologies based on the Internet, allow distribution of information and knowledge, being extremely suitable for establishment of the networks of agent type, for the concurrent design or work in virtual teams.

In conclusion, we can say that virtual enterprise is an entity in connection with a finite set of companies, being responsible with formulating economic objectives to meet customer needs as quickly as possible. For the consumer, virtual enterprise is a typical undertaking represented by a network structure type and for participants is an effort of integration and the creation of new types of interdependencies and relationships that can be addressed especially optimized in terms of agents and multiagent systems.

4. Advantages and disadvantages of virtual enterprise

1 Advantages

The virtual enterprise based on information and communication technologies for next generation, facilitates fast data transfers, low cost and coordination within the organization without geographical boundaries and time. The success of virtual enterprises is due to the following:

 the low cost facilitates the flexibility of the relationships between partners, answers prompt thereof, and individual firms focus on the core competences and on the effective activities;

 the flexibility of the virtual enterprises refers to the possibility of redefining the goals and the fast and competitive reconfiguration of the resources to respond quickly to market opportunities;

 efficiency is determined by flexible links between network partners and can quickly break these links.

2 Disadvantages

The virtual enterprises imply a number of limitations:

 the level of the technological capacities and accessibility may hinder full integration of virtual enterprises, wholly dependent on the quality of electronic information exchanged between the "players" whose transparency is doubtful;

 may appear a number of issues related to the sharing of profits, cost reduction and strategic policies, the intellectual properties and security;

 social implications, psychological effects on employees of virtual enterprises, the lack of direct interactions may raise conflict of loyalty and performance;

 although, the virtual enterprise, not assumes the hierarchical relationships, it is possible the dominance of the companies that form the core of the enterprise;

 the coalitions laws and a taxes, because the virtual enterprises, do not fall within statutory classifications, production can be placed there where legislation is more favorable.

5. Designing an architectures of the virtual enterprise using multi-agent systems

Infrastructure of a virtual enterprise should provide conceptual homogeneity of the resources, the information and the activities, security, trust and confidentiality and at the same time take into account the mutual requirements of its partners, interoperability and exchange of information in real time so that can work as an integrated unit and, at the same time ensure the independence and autonomy of partners.

In building a virtual enterprise are two important issues. The main problem is heterogeneity, which comes from different levels (technological, informational or procedural). The second problem is to develop a distributed workflow management system in virtual enterprise, which must integrate various business processes specific to each partner.

Typically, companies already exist before deciding to ally in a network of the sharing and exchange information. In addition, each enterprise is autonomous, independently developed by others and uses a separate management of the information and the control strategies to provide the best results. To ensure interoperability, each partner must have support for collaboration with other entities heterogeneous virtual enterprise that each node has two main modules:

 Internal Module - is an autonomous unit of a private companies, that includes the structure of the company's information (databases, information systems) and all internal processes of decision making;

 cooperation module - contains all functions for interconnection between companies and network, plays of role communication and coordination and works as an intermediary between the company and network.

This architecture enables companies willing to enter into a virtual relationship to define functions and interfaces of the business processes to enable a rapid and effective integration as a partner in virtual enterprise.

In the era of globalization, the virtual enterprise is faced with a multitude of offerings in the market, which are spread over a fairly large geographic area, called distributed business processes (DBP - Distributed Business Processes). Distributed economic processes represent a complex of the dynamic process and temporary which join together to development of the final product of the virtual enterprise. Because economics processes are performed by different individual businesses, the company which initiates virtual enterprise must coordinate the achieving of the process, to avoid chaos. Value chain management in virtual enterprises is very complex, especially in case of coordination problems.

Multiagent systems are a set of concepts and technologies through which studies the modalities complex of interactions between agents. Thus, each component of the real system, called the agent, has as correspondent an independent software program, by means of which is modeled its behavior and its relationship with the environment. Consequently, due to different the behaviors of systems and subsystems of the economic reality, we will have the heterogeneous programs that will operate independently of each other, but their interaction and the communication, highlight just the complexity of the real world. In a multiagent system, the interaction between agents can be achieved through collaboration, coordination and cooperation.

To fulfill its role in an organizational architecture of the virtual type, the agents must possess certain properties, considered basic, such as: responsiveness, deliberation, efficiency, ability to interact with other agents and adaptability. At the basis of design of autonomous agents which interact and which will form the basis for multiagent system design project in virtual enterprise (MAVE) is INTERRAP architecture in which the agent is represented as an interface to users, composed of a control unit and a base of knowledge.

The first phase of architecture of type agent in the virtual enterprise (MAVE - Multi Agents Virtual Enterprise) is to create a prototype that enables users located on different sites at large geographical distances, to bid for different partial processes of cycle supply-production-outlets, which will form global process of virtual enterprise. Both the auction process and phase by the information are supported by intelligent assistant agents. Steps need to be taken, shall be conducted in a logical sequence, as follows:

1. Planning the specifications

The first step involves planning the specifications (more informal, involving a moving from products to processes) on the provision of products and services by the virtual enterprise, then turning them into specifications (formal) of the economic processes that describe virtual enterprise, namely the description of highly complex procedures such as transforming informal tasks in formal specifications of program or definition of a process on the product description. Through the architecture of the information system ARIS (ARIS-The Architecture of Re-engineering Information System) will be an analysis of economic problems within a company by describing commercial processes, based on a model that is based on two general concepts: table virtual and the descriptive level.

To reduce the complexity of the model, is divided and described by individual virtual tables what representing architectural aspects (design) detailed individual. This decomposition of the general model (the level of definition of requirements, the level of specification description of the design, and the level of implementation of the new system) must be such that the individual views of different analysts can be understood independently using specialized methods.

Modeling the production process involves using the virtual table of control and the highest descriptive level, called the level of definition of the requirements, where economic processes are integrated in the chain management processes (EPCs - Chain Process Engineering System).

2. Decomposition of the processes

Global chain of processes can be decomposed into parts that can be assigned of the individual solvers of problems. It starts from the observation that the functionalities given by classic enterprise models (models supply, production, marketing, sales and distribution) are useful to show how it can be achieved vertical decomposition of tasks. Thus, the overall process chain is decomposed into parts of chain, on the basis of functionality.

3. Modeling of the agents and interactions between agents

The design of the activities of the virtual enterprise achieved in a dynamic and complex virtual environment so must make analysis of the systems by the agent type and interactions between them. In framework of the design proposed of the virtual enterprise architecture, each agent is designed in accordance with the INTERRAP architecture (Architecture Autonomous Agents).

The behavioral basic level of an agent includes its ability to react (reactive patterns of the behavior) used to monitor the new information relevant, from the network or to signal the introduction of a new agent, which means initiating a process of communication (bidirectional).

Local planning level of the agent contains local process description, namely abstract descriptions of the partial processes performed by agents of the virtual enterprise. At this level may be designed models and highlighted classification criteria, achieving thus evaluation of the processes local.

These local assessments form the decisions basis for the cooperation level planned, where are localized the knowledge that activates agencies for to participate in the auction. The knowledge require (in general models of negotiation proposed by Rosenschein and Zlotkin (1994)): a set of information to negotiate or set of acceptable results, the characteristics of the negotiation protocol, and the negotiation strategy. The protocols of the different forms of auction and strategies (reflecting the behavior of the agents towards risk) is implemented and experimentally assessed.

4. Modeling and evaluation processes

In the allocation phase, each partial process part of the overall process is activated by an auction process. Obtaining a partially process following the tendering process is based on a high level of the assessment of alternatives. In the bidding process is very important to develop appropriate function, to activate individual agents to assess the quality a partial process candidate . These functions require the use of classification criteria based on a formal description of partial processes. The result of the first phase of design is a restricted model, which, for a given area, allows decisions based on a limited set of classifications. Such a connection is made between part economic and technical enterprise.

The evaluation of the process depends on quantitative economic factors (such as during a partial process, its share in total production costs) and qualitative factors (such as quality of service to customers). Unlike most of the negotiation protocols considered in multiagent systems, the selection of the partial process in virtual enterprise is a problem of the multi-criteria decision. Thus, the selection of bidding is more complex than that protocol of the network agreement, where the selection of the best tender is a simple arithmetic process.

6. Coordination of economic processes in the virtual enterprises

In a virtual enterprise, usually there are several economic processes and their coordination is one of the most difficult tasks of multiagent system. The necessary requirements coordination is determined on the basis of the analysis of the activities within each phase of the life cycle of the virtual enterprise (creation, operation and dissolution).

With the development of information technology, can be advanced coordination of virtual enterprise operation, which involves a series of specialized software modules for implementing coordinated activities of virtual enterprise. Through a high-level software, is performed a integration of the activities by advanced coordination through a platform installed in the components systems of the enterprise (nodes) and their internal modules so that businesses can operate in a "transparent" , achieving a improvement of quality of the management of the process supply-production-sale (supply chain). Platform can contain two basic modules: the level of cooperation and the architecture of the coordination activities functional .

Level of cooperation comprises the software modules semi-autonomous that can provide the company a number of features related to the exchange of commercial data (Internet and WWW), of data on technical products, of information about the quality of products and services, the management of information and the tenders in the virtual enterprise. Communication between this module and the architecture of the activities by the functional coordination, and of both modules with exterior, is achieved by a communication protocol.

Architecture the coordination functional activities includes five modules: editing and configuring economic distributed processes, research of the producers, negotiation, logistics, publishing and configuring the contract.

Editing and configuring economic distributed processes - involves the definition of the processes and elaboration ad (to be distributed in www network to find companies interested and able to realize all or part) and any changes in the contract. The announcement comprises the needs and requirements to be met by a member, including: obligations and rights; proposal of costs; payment arrangements, technical information, rights of access, information to be monitored.

The research of the producers comprises activity by search for potential partners and subtask by the inclusion of a new partner in virtual enterprise, aimed at providing the necessary tools search of the potential producers before publishing a notice. Searching for a producer can be done in the following locations: in the internal database of the virtual enterprise, in the "yellow pages" or the directories of services, on the Internet, in economic virtual centers, by means of a decision support system.

Negotiation is found in the negotiation subtask, but and in reconfiguration activities of the virtual enterprise, and changes in the contract of the economic distributed processes. During creation a virtual enterprise can appear some discrepancies between the initiator requests (specified in the notice distributed) and the interest of producers, or may be situations difficult while a member of the virtual enterprise waives to achieve economic process distributed during the operation of enterprises virtual, which involves solving through a negotiation electronically process .

Configuring editing and signing the contract is specific of the subtasks of legal agreement, of the reconfiguration of the virtual enterprise and by amending of the contract of economic distributed processes. Effective contracting ("legal") of an component enterprise, is performed after the announcing process and negotiation, comprising two modules cooperative:

The elaboration of the contract - usually differs from one company to another, from one product to another, and can be done based on a model contract, a draft published earlier contracts. The contract will contain information about who will prepare the contract, who will negotiate the contract elements, possible penalties, and when is considered a task completed.

b) Electronic Signature - implies activity of acceptance of contractual conditions and signing. The main objective of this activity is to provide a digital way, sure, by send / receive of the contracts already signed.

Logistical support, aims at obtaining, providing and coordinating information to and from virtual enterprise, while permitting procurement process, manufacturing and selling in a reasonably efficient manner, and comprises three modules:

Supervision of the virtual enterprise - provides electronic ways of obtaining information from the manufacturers, so that businesses can plan their production steadily, since generally the enterprises businesses have trouble in getting information from partners about the real situation of contracted business processes that directly affect DBP, in this respect, companies will have to constantly recalculate actions, due to the occurrence of unexpected events which is reflected in delays, leading to an increase in overall costs.

b) the decision support for the Department of Logistics / Supply helps the company to assess various situations and take decisions quickly, especially under conditions of conflict. The system is working in optimal conditions, when receiving relevant information, appropriate and timely from the Supply Department. DSS contains several basic tools that ensure concordance between obtaining the best results and development time of the activities, having a strong interaction with end users.

Analysis of the virtual enterprise, involves extending the principles of classical systems analysis system that offers a holistic approach to virtual enterprise, and allows an analysis of its performance. This tool is effective given that receives real-time updates from members of the virtual enterprise. The coordinator has the ability to optimize requirements and capacity planning depending on flow supply-production-sales (actual and planned) of each member of the company, may review different aspects of the contract.

A view to implementing of the architectures by the functionalities coordination using different techniques depending on the architectures specific which are becoming increasingly heterogeneous, distributed, autonomous, which requires a high level of intelligence and cooperation between modules, are preferable the multiagent models and object oriented. Also, are taking into account the possibilities of the products and software platforms, used in solving specific problems and their social impact.

CONCLUSIONS

The explosion Internet phenomenon and of electronic markets have pushed "companies to reconsider their development strategies and increase market share, allowing primarily the solving common problems and frequently encountered in the business world, through the new means allowing increased efficiency and effectiveness. But, the Internet, also means improved communication between entities participating in the business, and this new solution fully exploit the true potential of the Internet, creating opportunities for new premises for the business-to-business relationships.

The virtual enterprises can be very effective to respond to rapid changes in consumer demands because they are market-oriented and customer and have a great ability to make value-added products. The management of these companies involves a dynamic and flexible allocation of abstract requests by manufacturers and production sites, which involves using appropriate methods, respectively multiagent methods.

Creating virtual enterprises is usually achieved, in view the value chain: suppliers-producers-customers, an important stage in this process being achieving a setup simulator that can test such chains in a dynamic way. Intelligent systems lead to the improvement accessibility and consumer benefits that make to be in continues expansion.

Because virtual enterprise is a distributed organization, coherence and unity of the activities and processes are heterogeneous and complex, it is optimal to use methods and models based on agents and multiagent systems. Following the studies we noted that the optimal combination between multiagent systems and building of virtual entity by production and distribution, may provide efficient solutions to very complex problems.