You can validate an XML document on demand or automatically when you save the document.

可以在需要时验证XML文档，或在保存文档时自动验证。

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AXIOM provides a virtual document model it expands on demand, building only as much of the tree structure document model representation as has been requested by the client application.

AXIOM提供了一种可以按需扩展的虚拟文档模型，仅构建客户端应用程序所请求的树结构文档模型表示。

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The plan stresses the need for versatility provided by an Army that is adaptable, expansible and networked, according to the document, which also recognizes the demand for affordability.

该计划强调组建一支适应性强、可扩展的网络化多功能陆军的必要性，同时也承认对负担能力的需求。

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Venezuelan President Chavez threatened to refuse to sign the declaration to protest Cuba's absence from the hemispheric gathering, and to protest the document's failure - as it is now reportedly written - to demand an end to the U.S.embargo of the island.

VOA: standard.2009.04.18

Diplomats at the United Nations are working on a document that would demand restrictions on oil and other commercial business with the Syrian regime if it refuses to implement the Annan peace plan for a cease-fire and a transitional government.

CNN: Clinton slams Russia, China over Syria

This usually means a refusal to supply a document or a piece of information on demand.

ECONOMIST: Jacob Soderman, wrist-tapper general

By the same token, a constitutional reform may be aimed at fixing imperfections in the system of representation or other imperfections that demand amendments from the original constitutional document.

CENTERFORSECURITYPOLICY: Chavez's repression continues