Network Working Group H. Xu Internet-Draft DB. Xiao Intended status: Experimental CCNU INC Expires: May 8, 2010 November 4, 2009 An Evaluation Framework for Data Modeling Languages in Network Management Domain draft-xiao-evaluate-dml-05 Abstract With rapid development of next generation networks, it is expected that a separate effort to study data modeling languages in the interest of network management should be undertaken. Based on a good understanding of the requirements of data modeling in next generation network management domain, evaluation on management data modeling languages becomes an essential way for the purpose of standardization to replace proprietary data models in the near future. Our project aims to establish a framework for evaluation to measure the capabilities of management data modeling languages in meeting those requirements by a set of criteria, which are modeling approaches, interoperability, conformance, extensibility, readability, data representation and security considerations. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 8, 2010. Xu & Xiao Expires May 8, 2010 [Page 1] Internet-Draft Evaluation on Data Modeling Languages November 2009 Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Xu & Xiao Expires May 8, 2010 [Page 2] Internet-Draft Evaluation on Data Modeling Languages November 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Proposed Evaluation Framework . . . . . . . . . . . . . . . . 5 2.1. Modeling Approaches . . . . . . . . . . . . . . . . . . . 5 2.2. Interoperability . . . . . . . . . . . . . . . . . . . . . 5 2.2.1. Protocol Independence . . . . . . . . . . . . . . . . 6 2.2.2. Naming Independence . . . . . . . . . . . . . . . . . 6 2.3. Conformance . . . . . . . . . . . . . . . . . . . . . . . 6 2.3.1. Backward Compatibility . . . . . . . . . . . . . . . . 6 2.3.2. Versioning . . . . . . . . . . . . . . . . . . . . . . 6 2.3.3. Definition of Event Notification Messages . . . . . . 7 2.3.4. Definition of Error Messages . . . . . . . . . . . . . 7 2.4. Extensibility . . . . . . . . . . . . . . . . . . . . . . 7 2.4.1. Extensibility of Data Structures . . . . . . . . . . . 7 2.4.2. Extensibility of Data Types . . . . . . . . . . . . . 7 2.4.3. Extensibility of Elements and Attributes . . . . . . . 8 2.5. Readability . . . . . . . . . . . . . . . . . . . . . . . 8 2.5.1. Human Readability . . . . . . . . . . . . . . . . . . 8 2.5.2. Machine Readability . . . . . . . . . . . . . . . . . 8 2.6. Data Representation . . . . . . . . . . . . . . . . . . . 9 2.6.1. Support of Hierarchical Data . . . . . . . . . . . . . 9 2.6.2. Specification of Configuration Data, State Data and Statistics Data . . . . . . . . . . . . . . . . . 9 2.7. Security Considerations . . . . . . . . . . . . . . . . . 9 2.7.1. Granularity of Access Control . . . . . . . . . . . . 10 2.7.2. Lock Mechanism . . . . . . . . . . . . . . . . . . . . 10 3. Validation . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Application of Proposed Framework to NETCONF-based Data Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 20 6. Security Considerations . . . . . . . . . . . . . . . . . . . 21 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. Normative References . . . . . . . . . . . . . . . . . . . 23 8.2. Informative References . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 Xu & Xiao Expires May 8, 2010 [Page 3] Internet-Draft Evaluation on Data Modeling Languages November 2009 1. Introduction The definition of Information Model (IM) and Data Model (DM) should be seriously considered for network management solutions. IMs always model Managed Objects (MOs) at a conceptual level and are protocol- neutral, while DMs are defined at a concrete level, implementing in different ways and are protocol-specific. As for each network management model, a data modeling language is quite necessary for the description of the managed resources. Obviously, the work on evaluating data modeling languages for the sake of next generation network management is comparatively indispensable. However, the fact is that a reused evaluation framework for management data modeling languages is still greatly lacking. The aim of our project is then to establish an evaluation framework to measure the capabilities of management data modeling languages in adapting to the requirements of ever-evolving network management and apply it to examine existing languages for validation. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Xu & Xiao Expires May 8, 2010 [Page 4] Internet-Draft Evaluation on Data Modeling Languages November 2009 2. Proposed Evaluation Framework Nowadays data modeling is under hot research, but it is still a preparatory period for corresponding research on network management. It becomes necessary to put forward a universal evaluation framework for data modeling languages to level their capabilities in satisfying the requirements of future network management. Proposed evaluation framework is based on a set of criteria, and through criteria aggregation, these criteria are adjusted into protocol-independent ones that are modeling approaches, interoperability, conformance and extensibility, and protocol-specific ones that are readability, data representation and security considerations. 2.1. Modeling Approaches Four main modeling approaches should be considered, including data- oriented one, command-oriented one, object-oriented/object-based one and document-oriented one. The data-oriented approach models all management aspects through data objects, and at least two operations ("get" and "set") should be defined. The command-oriented approach defines a large number of management operations, specifying not the details but the commands to get/set selected information. The object-oriented/object-based approach combines the data-oriented approach and the command-oriented approach in view of integration. The document-oriented approach represents state information, statistics information and configuration information of a device as a structured document. Future management data modeling language should implement an integration of various modeling approaches, a possible scenario of which is a data-oriented view for monitoring, a command-oriented view for operations and a document-oriented view for configuration. Note that, the very language should avoid implementing the same function with simple combination of these approaches. 2.2. Interoperability With the development of next generation networks, management in an environment with a heterogeneous set of devices becomes a trend. Hence, standardization of DMs for network management should work at a higher level, making them more close to IMs. Following this way, data modeling languages should accordingly provide interoperability, which is consistent with the understanding of MOs already learned by network operators. Xu & Xiao Expires May 8, 2010 [Page 5] Internet-Draft Evaluation on Data Modeling Languages November 2009 2.2.1. Protocol Independence Protocol independence means that the language defines management data supporting any protocol instead of belonging to some specific protocol. In other words, the DM defined by this language can be implemented on any platform that installs different protocols. In order to integrate with existing network management technologies, DMs should be defined by protocol-neutral modeling languages that can be mapped on different underlying protocols. 2.2.2. Naming Independence Naming independence is a desired mechanism provided by the language that specifies how name collisions are handled, and thus uniquely identifies attributes, groups of attributes, and events. Since a data modeling language for network management is required to be protocol-independent, and protocols typically use different approaches to name instances, it has to support multiple instance naming systems. Being naming independence, the language needs to think about the relationships between DMs. More efforts should then be made to ensure implementation of the language not being interfered by problems of different objects from multiple modules with the same name. 2.3. Conformance When defining MOs, it is also quite necessary to describe machine- readable conformance for the DM. 2.3.1. Backward Compatibility Backward compatibility illuminates that new versions of the data modeling language can be used to define the relevant DM for the purpose of network management as the older one used to do. This capability is quite important, for the reason that it eliminates the need to start over when a new data modeling language is used. From the viewpoint of network management, it means that new versions of the data modeling language that define management content can be rolled out in a way that does not break existing supporters. 2.3.2. Versioning Versioning explains that each version of the data modeling language is complete, thus easy to control. This capability promotes the maintenance of backwards compatibility and does not need to change to Xu & Xiao Expires May 8, 2010 [Page 6] Internet-Draft Evaluation on Data Modeling Languages November 2009 the new language if it is also backwards compatible. 2.3.3. Definition of Event Notification Messages Definition of event notification messages needs to be ensured by the data modeling language to allow a single definition of notification content to be sent either asynchronously or synchronously. Network management protocols are desired to support asynchronous notifications, and with regard to a future data modeling language, not only notification messages but also types of the events should be clearly identified. 2.3.4. Definition of Error Messages Definition of error messages indicates that error messages generated by network management applications should be recognized by the data modeling language. Error messages, which are created by applications as a result of performing network management operations against the related DM, need to be included in the modeling language. 2.4. Extensibility With increase of isomerization and complexity of the Internet, there is a great need for data modeling languages to have the ability to extend data structures, data types, elements and attributes easily for the practice of developing related software or systems to manage future heterogeneous networks. 2.4.1. Extensibility of Data Structures Extensibility of data structures shows that the data modeling language has the capability to add new data structures with no need to affect available ones, and thus expresses the relations among data effectively and operates on data effortlessly. 2.4.2. Extensibility of Data Types Extensibility of data types reveals that data types defined by the modeling language can be extended easily, so that the language can support various kinds of management data both simply and clearly. Considering application of future protocols to manage next generation networks, especially for the use of configuration management, more and more new data types should be added to satisfy different presentation needs. Xu & Xiao Expires May 8, 2010 [Page 7] Internet-Draft Evaluation on Data Modeling Languages November 2009 2.4.3. Extensibility of Elements and Attributes Extensibility of elements and attributes means that types of element nodes and attributes defined by the data modeling language shouldn't be too fixed to extend. When there is a need to add new types of elements or new attributes for existing elements, the operation of "creation" should be done properly conveniently. Objects of great variety need to be managed in next generation network management, which means the demand of adding object types. Hence, the data modeling language should have this capability, in order that everyone can manage the objects both simply and effectively. 2.5. Readability It is desired that management data modeling languages should be easily understood by both operators and computers. Human readability is necessary for convenient study and use. And machine readability is required to accelerate automatic process of network management, since both DMs and IMs are now being complemented by semantic models, where the meaning of concepts used in network management and relationships existing between them are made explicit. 2.5.1. Human Readability Human readability is the capability by which administrators can directly read and understand representations including input and output (requirements, responses, error messages, etc). Only if administrators conveniently read and understand meanings of the DM, can they efficiently write and use it. This also does favor to the interoperation between DMs and administrators. It is then desirable that all DMs used for a network management solution are well formed according to the data modeling language. 2.5.2. Machine Readability Machine readability refers to the feature that description of the relevant DM can be understood by computers, thus related applications can be quickly developed. Its implementation largely depends on semantic expressiveness, and its speed also has very close relation with the parse-ability of machines. Note that, each data modeling language has a different level of semantic expressiveness, which includes several facets like concepts, relations and behaviors, and it is not easy to measure semantic expressiveness. Nowadays, this problem can be temporally reduced to a problem of integrating different management data modeling languages. Xu & Xiao Expires May 8, 2010 [Page 8] Internet-Draft Evaluation on Data Modeling Languages November 2009 Future network management protocol aims in enabling the system to automate its management process. From this point of view, semantic expressiveness is quite essential for better machine readability. For example, the behavior defined by data modeling languages should be well understood, so that the automation requirements towards network management can be promoted and become much more promising. 2.6. Data Representation Traditional network management solutions are often not strong in configuration management mostly as a result of modeling problems related to data representation, such as configuration objects being not easily identified. Consequently, the level of data representation ability should be taken into consideration. 2.6.1. Support of Hierarchical Data Support of hierarchical data implies that hierarchical data can be clearly described by the modeling language so that it can be easily understood by both operators and computers. It is said to be better that management data defined by a modeling language should be hierarchical and emphasis should be placed on creating application-level ones especially for the configuration. 2.6.2. Specification of Configuration Data, State Data and Statistics Data Configuration data is the set of read-write data, while both state data and statistic data are read-only, only different in the scope of practical use. The DM specified for a network device should identify what is configuration data, what is state data and what is statistic data, without the trouble to separate container elements. When a device is performing configuration operations, a number of problems would arise if state data and statistic data were included in configuration data, and in order to account for these issues, future network management protocol should recognize the differences among state data, statistic data and configuration data, and provides operations for each. Thus as for the data modeling language, it then becomes necessary to make a clear distinction between (a) configuration data and (b) state data and statistic data. 2.7. Security Considerations Security cannot be ignored by modeling languages to ensure confidentiality and integrity of management data. Xu & Xiao Expires May 8, 2010 [Page 9] Internet-Draft Evaluation on Data Modeling Languages November 2009 2.7.1. Granularity of Access Control Granularity of access control refers to the precision of accessing data from the relevant DM. There are mainly two levels of granularity, which are coarse one and fine one. Using coarse granularity of access control, a bulk of data can be retrieved and edited from the DM, such as getting the whole data from MIB. And fine granularity refers to a detailed operation to a small part of data, such as elements. Both coarse granularity and fine granularity have their advantages and disadvantages. For example, implementation of coarse granularity is simple, while reusability is very poor. Hence, the tradeoff between coarse granularity and fine granularity becomes quite necessary for data modeling especially when merging and mapping information across multiple systems or data stores, since granularity may not match in the process of mapping. 2.7.2. Lock Mechanism Lock mechanism cannot be ignored by management data modeling languages in order to guarantee security of the configuration. As to some devices, it is quite hard to determine which parameters are administratively configured and which are obtained via mechanisms such as routing protocols. Taking configuration management into consideration, an implementation should figure out how users lock an entire configuration database, even if users do not have "write" access to the entire database. Furthermore, it is also of great importance to a partial lock of a configuration data store. Although it's not clear how serious this problem is, the solution is now an open issue. Xu & Xiao Expires May 8, 2010 [Page 10] Internet-Draft Evaluation on Data Modeling Languages November 2009 3. Validation The languages being measured are Guidelines for the Definition of Managed Objects (GDMO) for CMIP, Structure of Management Information (SMI) with its different versions for SNMP, Management Information Format (MIF) for DMI, Managed Object Format/Common Information Model (MOF/CIM) for WBEM, and Structure of Management Information, next generation (SMIng) for both SNMP and COPS-PR, all of which are available nowadays in the field of network management. First, Table 1 shows which modeling approach each language adopts in the interest of network management. As is indicated in Table 1, object-based approach is especially distinguished from object- oriented approach, since the former one is an incomplete version of the latter one. +----------------------------+------+-----+-----+---------+-------+ | | GDMO | SMI | MIF | MOF/CIM | SMIng | +----------------------------+------+-----+-----+---------+-------+ | Data-Oriented Approach | | # | | | | | | | | | | | | Command-Oriented Approach | | | | | | | | | | | | | | Object-Based Approach | | | # | | # | | | | | | | | | Object-Oriented Approach | # | | | # | | | | | | | | | | Document-Oriented Approach | | | | | | +----------------------------+------+-----+-----+---------+-------+ Table 1: Modeling approach adopted by each language Second, Table 2 illustrates the comparison result in terms of the evaluation criteria listed in Section 2 except for modeling approaches, the comparison on which has been presented in Table 1. Note that, our measurement is classified as the following four levels. a. A minus sign (-) means that the language does not have such a capability. b. An asterisk sign (*) denotes that the language is weak in this capability. c. A plus sign (+) is used when the language is good at this capability. Xu & Xiao Expires May 8, 2010 [Page 11] Internet-Draft Evaluation on Data Modeling Languages November 2009 d. Two plus sign (++) is placed when the language completely possesses this capability. It can be concluded from Table 2 that, SMIng is the language with best implementation of most criteria, while SMI and MOF/CIM are near SMIng capabilities. Xu & Xiao Expires May 8, 2010 [Page 12] Internet-Draft Evaluation on Data Modeling Languages November 2009 +------------------------------+------+-----+-----+---------+-------+ | Language | GDMO | SMI | MIF | MOF/CIM | SMIng | +------------------------------+------+-----+-----+---------+-------+ | Interoperability | | | | | | | | | | | | | | Protocol Independence | - | - | + | - | * | | | | | | | | | Naming Independence | - | - | - | - | - | | | | | | | | | Conformance | | | | | | | | | | | | | | Backward Compatibility | - | + | * | * | - | | | | | | | | | Versioning | - | - | - | + | * | | | | | | | | | Definition of Event | - | ++ | - | - | ++ | | Notification Messages | | | | | | | | | | | | | | Definition of Error | - | - | - | - | - | | Messages | | | | | | | | | | | | | | Extensibility | | | | | | | | | | | | | | Extensibility of Data | - | - | - | - | - | | Structures | | | | | | | | | | | | | | Extensibility of Data | - | + | - | + | + | | Types | | | | | | | | | | | | | | Extensibility of Elements | - | - | - | - | + | | and Attributes | | | | | | | | | | | | | | Readability | | | | | | | | | | | | | | Human Readability | * | * | * | * | + | | | | | | | | | Machine Readability | + | * | * | + | + | | | | | | | | | Data Representation | | | | | | | | | | | | | | Support of Hierarchical | - | * | - | - | - | | Data | | | | | | | | | | | | | | Specification of | - | - | - | - | - | | Configuration Data,State | | | | | | | Data and Statistics Data | | | | | | | | | | | | | | Security Considerations | | | | | | Xu & Xiao Expires May 8, 2010 [Page 13] Internet-Draft Evaluation on Data Modeling Languages November 2009 | Granularity of Access | - | + | - | - | + | | Control | | | | | | | | | | | | | | Lock Mechanism | - | - | - | - | - | +------------------------------+------+-----+-----+---------+-------+ Table 2: Summary of the compared characteristics Undoubtedly, existing data modeling languages play an important role in traditional network management. Especially, SMI has commendably implemented performance management in SNMP-based network management. However, networks have become more and more complex and heterogeneous as well, so DMs based on these data modeling languages don't seem to have enough ability to meet the requirements towards future network management. Using our proposed evaluation framework, the deficiencies of available languages have been clearly shown above, the main point of which is summarized as follows. a. All of them only use a single modeling approach not integration demanded by data modeling. b. Their interoperability is insufficient, though some efforts have been made. Traditional DMs are designed especially for certain protocols, always having close relation with specific operations of the protocols, and take their individual naming rules, way of expression, and so on, all of which lead to the poverty of universality in meeting the interoperable requirements of next generation network management solutions. c. Their human readability is quite weak, while their machine readability is also fairly poor, which is far from the automatic aim of next generation network management. d. Traditional DMs put emphasis on performance management, but take little consideration into configuration management. Future DMs should strengthen this point in order to satisfy a higher demand of configuration management, which has been clearly shown as one of the most important objectives of next generation network management. e. As for conformance required by data modeling, backward compatibility and versioning are two features that are related but with a different focus. Additionally, few of the languages lay emphases on definition of event notification messages with exception of SMI and SMIng, which are in full procession of this capability. Furthermore, all these languages pay no attention to definition of error messages. Xu & Xiao Expires May 8, 2010 [Page 14] Internet-Draft Evaluation on Data Modeling Languages November 2009 f. Their extensibility is quite deficient, which can not satisfy application needs of network management solutions. g. In DMs specified by traditional modeling languages, mechanisms related to access control and lock is so simple that it cannot satisfy the demands of network security and adapt to complex network operations as well. Additionally, the level of network security requirements is being higher and higher with the popularity of next generation networks. Xu & Xiao Expires May 8, 2010 [Page 15] Internet-Draft Evaluation on Data Modeling Languages November 2009 4. Application of Proposed Framework to NETCONF-based Data Modeling Using our proposed evaluation framework, we compare the possible NETCONF data modeling languages that are XML Schema, RELAX NG and YANG, the result of which is presented in Table 3 and Table 4. +----------------------------+------------+----------+------+ | | XML Schema | RELAX NG | YANG | +----------------------------+------------+----------+------+ | Data-Oriented Approach | | | | | | | | | | Command-Oriented Approach | | | | | | | | | | Object-Based Approach | | | # | | | | | | | Object-Oriented Approach | | | | | | | | | | Document-Oriented Approach | # | # | # | +----------------------------+------------+----------+------+ Table 3: Modeling approach adopted by compared languages Xu & Xiao Expires May 8, 2010 [Page 16] Internet-Draft Evaluation on Data Modeling Languages November 2009 +------------------------------------------+---------+-------+------+ | Language | XML | RELAX | YANG | | | Schema | NG | | +------------------------------------------+---------+-------+------+ | Interoperability | | | | | | | | | | Protocol Independence | ++ | ++ | - | | | | | | | Naming Independence | ++ | ++ | - | | | | | | | Conformance | | | | | | | | | | Backward Compatibility | + | + | + | | | | | | | Versioning | ++ | ++ | ++ | | | | | | | Definition of Event Notification | - | - | ++ | | Messages | | | | | | | | | | Definition of Error Messages | - | - | ++ | | | | | | | Extensibility | | | | | | | | | | Extensibility of Data Structures | ++ | ++ | ++ | | | | | | | Extensibility of Data Types | ++ | ++ | ++ | | | | | | | Extensibility of Elements and | ++ | ++ | ++ | | Attributes | | | | | | | | | | Readability | | | | | | | | | | Human Readability | + | + | ++ | | | | | | | Machine Readability | * | * | + | | | | | | | Data Representation | | | | | | | | | | Support of Hierarchical Data | ++ | ++ | ++ | | | | | | | Specification of Configuration | ++ | ++ | ++ | | Data,State Data and Statistics Data | | | | | | | | | | Security Considerations | | | | | | | | | | Granularity of Access Control | ++ | ++ | ++ | | | | | | Xu & Xiao Expires May 8, 2010 [Page 17] Internet-Draft Evaluation on Data Modeling Languages November 2009 | Lock Mechanism | - | - | ++ | +------------------------------------------+---------+-------+------+ Table 4: Comparsion result First of all, as is demonstrated in Table 3 and Table 4, it can be summarized that, most properties of XML Schema surpass those of previous data modeling languages, especially in aspects such as interoperability, data representation and extensibility, which have been quite well-known by its numerous users. However, its machine readability is not so satisfying, for the reason that, what it is accomplished in is not semantic expressiveness but content definition. Furthermore, compared to its wide application, XML Schema is both too complicated and excessively general as a data modeling language for special use only in the scope of network management. On the other hand, definition of a NETCONF-based management DM is much more than an XML instance document description, or in other words, XML Schema is still not expressive enough with a view to NETCONF-based data modeling. All these reasons above lead to the fact that, there are still no DMs defined by XML Schema yet. Currently, IETF Operations & Management (OPS) Area is focusing the solutions on SMI-to-XML Schema conversion and XSD for accessing SMIv2 DMs, since SNMP-based network management has been supplemented with a lot of proprietary MIB modules defined by different device vendors, and discarding MIB objects and SMI syntax when designing a new DM does reduce this benefit from experience of so many years. But more work has to be done on standardizing a NETCONF-based data modeling language for network management. Additionally, as is indicated in Table 3 and Table 4, the information modeling capability of RELAX NG is roughly equal with that of XML Schema for the sake of network management. And RELAX NG may be a little more advantageous than XML Schema in some aspects such as human readability and extensibility. At the same time, the mapping of YANG to Document Schema Definition Languages (DSDL, including RELAX NG) is also considered these days. Furthermore, it can also be seen from Table 3 and Table 4 that, as a NETCONF-specific data modeling language, YANG takes semantics such as notification message definitions, error message definitions and lock mechanism into consideration. All these features make YANG much easier to describe DMs in a way that maps to NETCONF in a very straight-forward manner, and due to its focus on the immediate requirements for NETCONF-based network management, YANG has been chosen as the best approach up to now. Xu & Xiao Expires May 8, 2010 [Page 18] Internet-Draft Evaluation on Data Modeling Languages November 2009 As for data modeling languages in network management domain, YANG is designed at the semantic level, while XML-related languages are at the syntactic level. That is to say, description by YANG is at a semantic level, and XSD can be generated from the DMs defined in YANG. Thus in this case, existing tools can be utilized. To sum up, YANG seems to be much more appropriate than XML Schema for NETCONF-based data modeling, due to its focus on immediate requirements for the NETCONF protocol, and in order to meet requirements that potentially have broader applicability, XML Schema and RELAX NG need to be improved by providing more supports for the purpose of NETCONF, while YANG needs to be improved by providing more supports in the interest of protocol independence. Xu & Xiao Expires May 8, 2010 [Page 19] Internet-Draft Evaluation on Data Modeling Languages November 2009 5. Conclusions An evaluation framework for management data modeling languages has been established and validated by applying it to summarize the characteristics of existing languages through comparison. This framework is universal and can be reused to study data modeling in next generation network management domain. Future work includes further study on application of this framework to NETCONF-based data modeling, aiming to promote the standardization progress of data modeling languages for NETCONF-based network management. Xu & Xiao Expires May 8, 2010 [Page 20] Internet-Draft Evaluation on Data Modeling Languages November 2009 6. Security Considerations None. Xu & Xiao Expires May 8, 2010 [Page 21] Internet-Draft Evaluation on Data Modeling Languages November 2009 7. IANA Considerations None. Xu & Xiao Expires May 8, 2010 [Page 22] Internet-Draft Evaluation on Data Modeling Languages November 2009 8. References 8.1. Normative References [RFC1155] Rose, M. and K. McCloghrie, "Structure and identification of management information for TCP/IP-based internets", STD 16, RFC 1155, May 1990. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. Schoenwaelder, Ed., "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999. [RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J. Schoenwaelder, Ed., "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999. [RFC2580] McCloghrie, K., Perkins, D., and J. Schoenwaelder, "Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999. [RFC3216] Elliott, C., Harrington, D., Jason, J., Schoenwaelder, J., Strauss, F., and W. Weiss, "SMIng Objectives", RFC 3216, December 2001. [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between Information Models and Data Models", RFC 3444, January 2003. [RFC3535] Schoenwaelder, J., "Overview of the 2002 IAB Network Management Workshop", RFC 3535, May 2003. [RFC3780] Strauss, F. and J. Schoenwaelder, "SMIng - Next Generation Structure of Management Information", RFC 3780, May 2004. [RFC3781] Strauss, F. and J. Schoenwaelder, "Next Generation Structure of Management Information (SMIng) Mappings to the Simple Network Management Protocol (SNMP)", RFC 3781, May 2004. [RFC4741] Enns, R., "NETCONF Configuration Protocol", RFC 4741, December 2006. Xu & Xiao Expires May 8, 2010 [Page 23] Internet-Draft Evaluation on Data Modeling Languages November 2009 8.2. Informative References [RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart, "Introduction and Applicability Statements for Internet- Standard Management Framework", RFC 3410, December 2002. Xu & Xiao Expires May 8, 2010 [Page 24] Internet-Draft Evaluation on Data Modeling Languages November 2009 Authors' Addresses Hui Xu Institute of Computer Network and Communication Huazhong Normal University WuHan, HuBei 430079 P.R. China Phone: +86 027 6136 8682 Email: xuhui_1004@hotmail.com Debao Xiao Institute of Computer Network and Communication Huazhong Normal University WuHan, HuBei 430079 P.R. China Phone: +86 027 6786 6108 Email: dbxiao@mail.ccnu.edu.cn Xu & Xiao Expires May 8, 2010 [Page 25]