49、cture may follow the silo model. In this section, a number of these are listed. Few products embody all of these problems. But most contain instances of at least one of these problems. And even a single instance of the silo model is enough to prevent a learning resource or architecture from being us 。

50、ed as part of a network. Proprietary StandardsA standard is proprietary when it is secret or when patents, copyrights or other restrictions prohibit its use. The standard is created by a commercial entity and specifies “equipment, practices, or operations unique to that commercial entity.” (National 。

51、 Communications System, 1996) With the advent of the internet, proprietary standards are much less of an issue than in years past. Nonetheless, proprietary standards continue to abound, especially in the realm of multimedia formats. The use of a proprietary standard divides a distribution network in 。

52、to those people or systems able to use the standard, and those people or systems unable to use the standard. For example, a document created using DXF for Autocad may not display properly in Cadkey, which uses CADL, or ACIS, which uses SAT. Another example is XrML, a digital rights management langua 。

53、ge developed by ContentGuard. Developers have been reluctant to use the standard because of Microsofts control over the standard. (DRM Watch, 2002)Proprietary standards pose numerous risks to developers. One risk is that the standard will cease to be supported in new software. Documents encoded in o 。

54、lder MS Word formats, for example, need to be converted before they can be used. There is the risk that licensing terms may change, and as a consequence, require that user pay unexpected licensing fees. If the standard is not widely shared or distributed, as is the case, for example, with Microsoft。

55、Windows, it is difficult to develop new applications, and the holder of the standard enjoys an advantage over competing products. Additionally, the choice of viewing software may be limited. Because of these risks, it is difficult to encourage wide adoption of proprietary standards. Several of the s 。

56、ystems listed in the previous section depend in whole or in part on proprietary standards. Course packs designed for Web CT, for example, cannot easily be used in competing learning management systems. It is necessary to use a content migration utility (some versions of which are no longer supported 。

57、) to obtain interoperability. Overly Strict StandardsEven when a standard is non-proprietary, it may be the case that the standard is too limiting for widespread use. If, for example, a standard requires that only a limited type of data will be transported by a data transmission system, then novel a 。

58、pplications using different types of data will be impossible to develop. Much of the criticism around the Sharable Content Object Reference Model (SCORM) was focused on this sort of objection. SCORM was developed to support self-study modules designed for use by the U.S. Military. Learning objects d 。

59、efined using SCORM are mutually independent, meaning that only the most basic sort of sequencing is enabled. This has led critics to suggest that SCORM is not flexible enough to allow for a variety of pedagogies. (Welsch, 2002)In a similar manner, transport protocols may also be too strict. Just as, 。

60、 for example, a road is much less strict (and therefore much more widely used) than a railroad, so also a distribution network that delivers only learning objects (and not, say, journal articles) is less likely to be used than a network that delivers both.Some of the systems described in the previou 。

61、s section adhere to standards that are too strict. Any system requiring SCORM compliance, for example, will be viewed in this way. So also will repositories that list learning objects only, such as Merlot. Standards may be unreasonably strict in other ways. The GNU General Public License (GPL), for。

62、example, requires that any product developed using GPL software must also be GPL. Since the GPL is intended “to make sure the software is free,” all modifications of GPL software must also be free. (GPL. 1991) While the purpose of this condition is to ensure that developers cannot convert a GPL appl 。

63、ication into a proprietary application, the interpretation is that GPL prohibits the development of any proprietary applications within a given application environment. (Microsoft, 2002) Another issue related to the strictness of standards in the complexity of the standard in question. If the standa 。

64、rd is too complex, use of the standard requires an involved process or development tool. Legacy content, which might have met a laxer standard, must be converted to the new standard. XrML has been criticized because of its complexity (DRM Watch, 2002) as has SCORM (Welsch, 2002).Monolithic SolutionsUnder the name of “enterprise solutions,” learning content management systems have become tightly integrated monolithic software bundles. Such integration is even touted as a benefit by many software companies. Saba Softwa 。

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标题：Design|Design and reusability of learning objects in an academic context A new economy of education( 四 )